Ingestible electronic devices have the potential to obviate many of the challenges associated with chronic implants such as risk of infection, chronic inflammation, and costly surgical procedures. Examples of ingestible electronics include edible cameras, ingestible event monitors, and integrated smart drug delivery systems. Ingestible devices have made great advances in the early detection and improved treatment of disease by using commodity polymers and off-the-shelf electronic components. However, currently available materials fundamentally limit how these devices can be used. The potential clinical impact of ingestible electronics could be increased by expanding the application-specific materials toolbox for this class of medical devices. This talk will describe recent advances in bioinspired materials for potential use in edible devices. Examples include flexible biodegradable elastomers as structural polymers and melanin-based pigments as materials for on-board energy storage. Structure-property-processing relationships for these medical materials will be emphasized and prospective uses for these application-specific materials will be discussed.

Green electronics using biodegradable materials, such as protein-based polyelectrolytes, have attracted much interest in recently years because they are safe, nontoxic, and friendly to environment. In this article, we demonstrated two kind of green electronics devices, organic thin film transistor (OTFT) and triboelectric generator (TEG) fabricated with protein-based polyelectrolytes. In OTFT, protein was selected as gate dielectrics. The effective mobility of the device could be enhanced 30-40 times and the threshold voltage value reduced 10-20 times by varying the relative humidity from vacuum to air ambient. In TEG, protein also was chosen as the contact thin film. When the relative humidity was raised from 20% to 60%, the output open-circuit voltage increases to 40-50V and the output short-circuit current increases to 1-2 mu;A. These devices were demonstrated to be potential humidity sensors with good stability and durability
References:
1.Lung-Kai Mao, Jenn-Chang Hwang, Ting-Hao Chang, Chao-Ying Hsieh, Li-Shiuan Tsai, Yu-Lun Chueh, Shawn S.H. Hsu, Ping-Chiang Lyu, Ta-Jo Liu, Pentacene organic thin-#64257;lm transistors with solution-based gelatin dielectric, Organic Electronics, 2013, 14, 1170.
2.Chun-Yi Lee, Jenn-Chang Hwang, Yu-Lun Chueh, Ting-Hao Chang, Yi-Yun Cheng, Ping-Chiang Lyu, Hydrated bovine serum albumin as the gate dielectric material for organic #64257;eld-effect transistors, Organic Electronics,2014, 14, 2645.
3.Ting-Hao Chang, Chen-Pan Liao, Jen-Ching Tsai, Chun-Yi Lee, Jenn-Chang Hwang, I-Min Tso, Yu-Lun Chueh, Ping-Chiang Lyu, Jon-Yiew Gan, Natural polyelectrolyte: Major ampullate spider silk for electrolyte organic #64257;eld-effect transistors, Organic Electronics, 2014, 15,954.

A recent trend in bioelectronics research focuses on the employment of biological and bioinspired materials to realize electronic devices that can operate non-invasively in contact with and within the human body. In particular, increasing efforts are being devoted to the design and production of edible electronic devices that target some relevant biomedical applications, such as gastrointestinal tissue stimulation, monitoring of patients adherence to medications and controlled drug delivery.
The aim of this study is to show that entirely edible organic transistors, both p-type and n-type, can be directly ink-jet printed on a commercial pharmaceutical capsule by using materials that are either biocompatible, nature derived or commonly used in the food industry. The transistor bottom-contacts and top-gate electrode consist of PEDOT:PSS, a very well known conducting polymer, also widely employed as a highly conformable neural electrode. Alternative conductive materials can be adopted, e.g. edible gold used for food decoration. Shellac, a biodegradable bug secreted resin, acts both as smoothing layer and dielectric. Hydrogen-bonded organic pigments such as quinacridone, indigoids and perylene derivatives offer very promising performances as organic semiconductors, reaching hole and electron mobilities exceeding 10^-2 cm²V^-1s^-1 depending on the specific small molecule and deposition techniques. These organic pigments are practically insoluble in water and in many other organic solvents because of the strong intermolecular interactions ascribable to the H-bonds. For this reason the small molecules are deposited exploiting cleavable solubilizing tert-butoxycarbonyl (t-BOC) groups which are then removed by means of exposure to trifluoroacetic acid vapors. The t-BOC groups removal activates the latent H-bonds of the pigments which become completely insoluble and therefore exhibit an extremely low toxic potential, even lower than common food colourings. Moreover, these compounds can be functionalized with proteins without altering their electrical transport properties and the biological functionality of the proteins.
The present work thus demonstrates the all-printed realization of both p-type and n-type transistors on a commercially available pharmaceutical capsule. These devices hold considerable potential as basic multifunctional platforms for biosensors and bioactuators meant to operate within the gastrointestinal tract, as well as building blocks for an emerging class of biomedical devices dedicated to the monitoring of patients compliance to pharmacological treatments.
Rivnay, J., et al. (2013). Chem. Mater., 26(1), 679-685.
Kim, Y. J., et al. (2013). J. Mater. Chem. B, 1(31), 3781-3788.
Irimia-Vladu, et al. (2010). Adv. Funct. Mater., 20(23), 4017-4017.
Fattahi, P., et al. (2014). Adv. Mater., 26(12), 1846-1885.
G#322;owacki, E. D et al. (2013). Adv. Mater., 25(11), 1563-1569.

In a global e-waste totaling ~42 million tons for the year 2014 and expected to surge 33% by 2017, the humanity has already a difficult problem to address-according to the GLOBAL E-WASTE MONITOR 2014 of the United Nations University&’s Institute for the Advanced Study of Sustainability. One alternative to counteract the e-waste could be the fabrication of electronics either with earthly abundant-naturally occurring materials, or with materials derived from them. Our group investigated a large number of natural and nature-inspired materials as substrates, dielectrics, semiconductors and smoothening layers for the fabrication of organic field effect transistors and organic solar cells. The invited presentation will focus on the highlights of our recent research, especially with respect to natural dielectrics (cellulose and cellulose derivatives, waxes, gums, various grades of natural Shellac), flexible substrates resistant to high temperature processing exceeding 200 deg. C (plasticized Shellac) as well as natural and nature inspired semiconductors in the families of indigos, anthraquinones and acridones.

The diverse set of biological electron transport mechanisms continues to be a key source of inspiration for the development of new technologies such as biofuel cells and dye-sensitized solar cells. We focus on an interesting recent example, which involves external electron transport through biological nanowires by the bacterium Shewanella oneidensis [1]. In particular, this form of electron transport allows the bacterium to reduce heavy metals, which has the potential for environmental applications. The nanowires are constructed from cytochrome proteins that arrange stacks of heme molecules through which the transport process takes place. However, the details of this electron transport are difficult to study directly, so we take a computational approach to examine the microscopic mechanism. Using density functional theory (DFT), we set up a system of stacked heme molecules taken from the protein structure of the bacterial nanowire. Then, using time-dependent density functional theory (TDDFT), we simulate electronic excitations as well as charge injections, non-adiabatically propagating the electronic system using TDDFT with the ions following Ehrenfest dynamics. Our simulations reveal the complex nature of electron transfer through bacterial nanowires, and we hope that such a microscopic understanding of this unique electron transport mechanism will aid in the development of new bio-inspired applications.
[1] Breuer, M., Rosso, K. M., & Blumberger, J. (2014). Electron flow in multiheme bacterial cytochromes is a balancing act between heme electronic interaction and redox potentials. Proceedings of the National Academy of Sciences, 111(2), 611-616.

Stretchable conductive metallic structures are essential elements in the development of stretchable electronics. Current progress in this field has been mostly focused on man-made materials and structures for achieving high conductivity and high tensile strains.[1] On the other hand, there are many natural structures that show inherently good stretchability, but they are not electronically conductive. This talk will discuss our latest development of stretchable metal electrodes (either opaque or transparent) on the basis of biologic al templates. Two particular examples will be discussed in detail. The first one is the fabrication of highly stretchable opaque metal electrodes and interconnects, namely “Electronic Petals (E-petals)”, which make use of the topographical micro/nano structures of rose petals to enable superb stretchability to metal thin films.[2] The second example is the fabrication of stretchable transparent electrodes, namely “Vein-based Transparent Electrodes (VTEs)”, by chemical deposition of metal on natural veins of leaves.[3] We demonstrate that these bio-inspired electrodes possess remarkable electro-mechano-opto properties that outweigh most best-performing man-made ones.
References
1. Y. Yu, C. Yan, Z. J. Zheng*, Adv. Mater.2014, 26, 5508-5516.
2. R. Guo, Y. Yu, J. Zeng, X. Liu, X. Zhou, L. Niu, T. Gao, K. Li, Y. Yang, F. Zhou,* Z. J. Zheng*, Adv. Sci.2015, 2, 1400021.
3. Y. Yu, Y. Zhang, K. Li, C. Yan, Z. J. Zheng*, Small2015, DOI: 10.1002/smll.201500529.

In PEDOT:PSS, the PSS polyanion serves as the primary dopant making the p-type PEDOT phase to become electronically conductive. DMSO is commonly added to PEDOT:PSS emulsions to impact the nano-morphology of resulting deposited thin films. By adding this secondary dopant the conductivity of PEDOT:PSS thin films is increased and can reach beyond 1000 S/cm. In the hydrated state, PSS can exhibit high cationic conductivity, in fact reaching 1 mS/cm. The high combined electronic and ionic conductivity of hydrated PEDOT:PSS thin films makes the material system excellent as the electrode and channel in electrochemical transistors, sensors, super-capacitors, fuel cells, bioelectronic delivery devices and more. Further development of these devices, and their crucial device parameters, would benefit from achieving high combined ionic-electronic conductivity in bulky electrode and channel geometries in 3D. However, it has been proven utterly difficult to reach large-scale, easily processable and stable bulky 3D-electrode configurations based on organic materials in general and on PEDOT:PSS in particular.
Nanofibrulated cellulose (NFC) is a 3D-scaffold nano-fiber system that is derived from cellulose biomass. NFC is a truly green material and has a low density, high mechanical properties, is stable in aqueous media, possesses several economic values and is also renewable. It turns out that PEDOT:PSS form conformal coatings along individual NFC fibers and the resulting morphology appears also open for the migration and transport of ions. Large-scale 3D-electrodes, reaching centimeters in size, based on PEDOT:PSS-NFC exhibit 1000 S/cm electronic conductivity in the PEDOT phase and a high ionic conductivity beyond 10 mS/cm. The resulting PEDOT:PSS-NFC electrode has been explored in super-capacitors, electrochemical transistors and conductors resulting in outstanding and record-high device parameters, such as an associated charge storage capacity, transconductance and current levels of 1 F, 1 S and 1 A, respectively.

Thin film transistors employing inorganic or organic semiconductors have proven useful for sensing applications in aqueous environments. Materials stability in aqueous media is a critical parameter for device design and a boundary condition of eventual practical applications. The operational stability of organic semiconductors has improved, but has remained limited. Herein we report on the hydrogen-bonded organic pigments epindolidione and quinacridone as water-stable semiconductors. Low-voltage field-effect transistors show remarkable operational stability in aqueous environments in a pH range of 1-10 without any passivation [1]. We evaluate the effect of the ionic solutions on the transistor characteristics and the impact of insulating the source-drain contacts. Liquid environments do not appreciably effect the saturation current in transistors, however the off current is found to depend on the dielectric constant of the liquid with σprop; e^ε. This is interpreted in terms of an intercrystallite hopping model. The range of stability is unprecedented for organic semiconductors and most inorganic semiconductors as well and suggests these materials are highly suitable for applications in aqueous sensing devices.
[1] Eric Daniel Glowacki, Giuseppe Romanazzi, Cigdem Yumusak, Halime Coskun, Uwe Monkowius, Gundula Voss, Max Burian, Rainer T. Lechner, Nicola Demitri, Günther J. Redhammer, Nevsal Sünger, Gian Paolo Suranna, Serdar Sariciftci, Epindolidiones—Versatile and Stable Hydrogen-Bonded Pigments for Organic Field-Effect Transistors and Light-Emitting Diodes, Adv. Func. Mat., 25, 5, 2015

We demonstrate the direct bioconjugation of hydrogen-bonded organic semiconductors with two different complex functional proteins in an aqueous environment. The representative semiconductors are vacuum evaporated epindolidione and quinacridone
These molecules in thin films react spontaneously with N-hydroxysuccinimide functionalized linkers. Using covalent attachment for Rhodobacter sphaeroides reaction centre (RC) and the biotin-streptavidin lock-and-key system, the proteins were bound to the semiconductors, conserving their biofunctionality.
Surface-functionalization by linkers was investigated by Attenuated Total Reflection, Fourier Transform Infrared Spectroscopy ATR-FTIR, water contact angle measurements, and atomic force microscopy. Presence and integrity of the RC was investigated by charge recombination assay, in the case of biotinylation a quantum-dot labelled streptavidin was used. Preliminary results of investigations with biofunctionalized AFM will be presented, also.
As key results, our work shows that upon bioconjugation, the semiconductors preserve their favourable electrical properties even under water making hydrogen-bonded semiconductors promising platforms for bioelectronics devices.

A wide variety of biological small molecules in nature are able to self-assemble into complex supramolecular structures. The products of these self-assembly processes are held to exacting standards, since their features and size are fundamental to the correct functioning of organisms. The ability to mimic the self-assembly behavior of these molecules to fabricate soft matter materials with interesting optoelectronic characteristics has focused the attention of many researchers. Among the studied materials, eumelanins are a particularly interesting candidate due to an ensemble of different characteristics. However, its structure/function interrelationships within the polymer are still under debate. With the aim to provide insights on the matter, we have been investigating the non-covalent interactions between eumelanin monomers.
In this work, we describe the behavior of one of the eumelanin monomers, 5,6-dihydroxyindole-2-carboxylic acid (DHICA) and its close relative indole-2-carboxylic acid (I2CA) on various metal substrates in Ultra High Vacuum condition. Once on the substrate, the molecules of I2CA form wide 2D structures, with a chevron-like morphology that is relatively independent from the substrate or preparation condition. The increased functionalization of DHICA leads instead to the formation of different structures that are strongly dependent to the substrate reactivity and periodicity that we have investigated by Scanning Tunneling Microscopy (STM). The low symmetry of the molecules, given by the presence of the pyrrole ring, leads to several conformations for each bonding disposition: only with the aid of density functional theory (DFT) calculations, we were able to gain insights of the molecular network structures. From these results, we investigate how the initial monolayer structure can affect the growth of device-ready thin films. By using Kelvin probe force microscopy (KPFM) and impedance spectroscopy, we are able to investigate how different monolayer structure would affect the charge injection in the film.

The unique and diverse functions of biomaterials provide many opportunities in developing concepts, as well as new classes of materials and devices. The knowledge gained in understanding how biological materials are constructed and function has enabled the design of bioinspired/derived functional materials with tailored properties for optics, sensing, catalysis and electronics. We have employed experimental and computational approaches to understand structure-function relationships for the development of biomimetic materials, tailoring interfacial properties features and fabricating functional materials for the development of photonic ad electronic devices based on these biomimetic materials will be discussed. In this talk, I will highlight our efforts on using our fundamental understanding of biomolecular interactions, factors that influence bio-nanomaterials interactions and demonstrate the fabrication of biomimetic materials for sensing, catalysis and decontamination applications.

Eumelanins, the black insoluble pigments of human skin, eyes and substantia nigra (neuromelanin), stand today as a unique source of inspiration for the design and implementation of soft biocompatible multifunctional materials for bio-optoelectronic devices.¹ Interest in eumelanins stems from bioavailability, biocompatibility and a peculiar set of physicochemical properties, i.e. broadband absorption in the UV-visible range, intrinsic free radical character, water-dependent hybrid ionic-electronic conductor behaviour, supporting optimistic feelings about a possible rise of eumelanin-mimics as innovative bioinspired solutions for organic bioelectronics.²
However, a number of conceptual and technological gaps still hinder a rapid progress of melanin-based organic electronics and bioelectronics, including in particular the limited contribution of electronic conductivity and current decay with time under biasing. Herein, we provide a concise overview of the structural and optoelectronic properties of melanins with a view to bringing to focus main issues and challenges en route to bioelectronic applications. Basic structure-property function relationships, fundamental tailoring strategies, processing and the balance of ionic-electronic processes will be addressed along with representative examples of eumelanin-based hybrids to orient ongoing efforts toward efficient and competitive eumelanin-based technology.
(1) d'Ischia, M.; Napolitano, A.; Pezzella, A.; Meredith, P.; Sarna, T. Angew Chem Int Edit2009, 48, 3914-3921.
(2) Organic Electronics: Emerging Concepts and Technologies Fabio Cicoira (Editor), Clara Santato (Editor) ISBN: 978-3-527-41131-3 464 pages September 2013

Eumelanin is a dark-brown pigment present in animals, fungi and microorganisms, featuring functions such as thermoregulation, photoprotection, free radical quenching and properties such as biodegradability, biocompatibility and mixed ionic-electronic conduction [1]. Furthermore, the two types of indolic building blocks impart to eumelanin metal-chelation properties [2].
In hydrated eumelanin thin films deposited between Au electrodes, upon application of an electrical bias (1 V), dendritic nanostructures have been observed, leading to a steep current increase [3]: the phenomenon was due to the combined action of the chlorides present in the pigment and of its chelating units and resembled the resistive switch taking place in memory devices, thus opening to the perspective of using eumelanin for such kind of applications.
Here we report on nanostructures forming in eumelanin films between metal electrodes (Au, Pd and Ag of relevance in microelectronics and Fe and Cu of relevance in biology). Sigma (synthetic, from tyrosine), Sepia (natural, from Sepia Officinalis) and DMSO melanin (synthesized in dimethylsulfoxide, thus featuring sulphonated groups) were used. Sigma and Sepia melanin differ in the ratio of the two indole building blocks and in the chloride content, whereas DMSO melanin lacks the phenolic hydroxyls groups, likely responsible for the chelation of multivalent cations. The formation of nanostructures was studied by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). Preliminary results on both Sigma and Sepia melanin thin films processed in DMSO suggest that the time needed for the formation of nanostructures in the case of Au electrodes is strongly dependent on the amount of chlorides present, with a threshold-like behavior. Counter experiments with pure solvent DMSO showed partial dissolution of the electrode, but no dendrite formation, confirming the role of melanin as a chelating agent and nanostructure-growth favourable matrix. Results on Pd electrodes (Sigma melanin with Cl- 8% w/w) show terrace-shaped bridging structures. We are at present establishing an extended correlation between parameters such as biasing time, chemical eumelanin composition, shape and size of the eumelanin nanostructures to increase the current knowledge of the interactions between the pigment eumelanin and metals, and to give a further insight into the possibility of using eumelanin thin films in memory devices.
[1] M. d&’Ischia et al, Pigm Cell Melanoma R, 26, 5, 616-633, 2013.
[2] L. Hong and J. Simon, J Phys Chem B, 111, 28, 7938-7947, 2007.
[3] J. Wünsche et al, Adv Funct Mater, 23, 45, 5591-5598, 2013.

Biocompatibility and biodegradability make the pigment eumelanin (EuM), which is based on dihydroxyindole and dihydroxyindole carboxylic acid building blocks, an interesting candidate for applications in bioelectronics and sustainable electronics.
In addition, the efficient and reversible charge storage properties of EuM in aqueous electrolytes permits to exploit it as an electrode in electrochemical energy storage/conversion devices, such as batteries and supercapacitors.
Here we report on aqueous micro-supercapacitors making use of EuM-based electrodes.
A preliminary characterization of EuM drop casted on a current collector made of carbon paper (EuM/CP) was performed by cyclic voltammetry (CV) at different scan rates. Different aqueous electrolytes such as ammonium acetate buffer at pH 5.5, sodium sulfate at pH 5.5, phosphate buffered saline at pH 7.4, and ammonia buffer pH 10 were used to test the effect of the pH and of the nature of the electrolyte ions on the storage properties. At pH 5.5, EuM electrodes featured a specific capacitance values as high as 150 F g^-1, which is of great interest for supercapacitor applications. The catechol-quinone moieties present in the EuM and the proton conducting properties of EuM are likely responsible for the reversible pseudocapacitive current observed. Other moieties, such as COOH and aromatic amines, also play a role in determining the pseudocapacitive behavior of eumelanin.
EuM/CP supercapacitors in ammonium acetate buffer at pH 5.5 where tested by repeated galvanostatic charge/discharge cycles between 0 V and 0.75 V at various current densities, namely 0.25, 0.50, 1.25, 2.50, 12.50 mA cm^-2 with the highest current corresponding to ~90 A g^-1 of EuM. The EuM/CP supercapacitors featuring 27 µg of EuM loading displayed a maximum energy density of ~0.1 mWh cm^-2 and a maximum power of ~20 mW cm^-2. The cycling stability of the EuM/CP supercapacitor was demonstrated over 100,000 charge-discharge galvanostatic cycles.
Based on such promising results, flexible bio-micro-supercapacitor were fabricated on polyethylene terephthalate (PET) substrates by conventional lithography technique using Ti/Au as current collector. The conductive carbon Super C-65 and polyvinylidene fluoride (PVDF) binder were blended with eumelanin. The flexible bio-micro-supercapacitor was able to operate at very fast CV scan rates (up to 10 V s^-1). These results suggest that EuM based bio-micro-supercapacitor may serve as biodegradable power source for implantable medical devices.

Integrins, as transmembrane heterodimeric receptors, take over important functions in cell adhesion, migration, proliferation, survival (apoptosis), and signal transduction, in many physio- as well as pathophysiological settings. Characterization of integrins and their ligand/antagonist binding is notoriously difficult due to high integrin redundancy and ubiquity. Bypassing the intrinsic difficulties of cell-based integrin expression, purification, and reconstitution, we present for the functional analysis of such the synthesis of a heterodimeric integrin receptor assembled into a block-copolymeric membrane mimic. We present synthesis and function (interfering in cell adhesion) of functionally active integrin avszlig;3, generated by in vitro membrane-assisted protein synthesis (iMAPS) involving motility studies based on labeling with ligand - functionalized quantum dots as 'molecular lanterns'. This work presents a robust and adaptable polymer-based platform for characterization of time and space resolved integrin - ligand interactions.

Magnetite (Fe₃O₄) is a widespread magnetic iron oxide encountered in geology as well as biomineralization, which also has many technological applications. Its magnetic properties depend largely on the size and shape of the crystals, and at room temperature only 20-80 nm particles display single-domain ferrimagnetic behavior. In nature, magnetotactic bacteria are encountered that indeed produce chains of aligned uniform and monodisperse magnetite crystals in this size range, thereby optimally utilizing their magnetic properties for navigation in the Earth&’s magnetic field.
Although biology achieves such control by applying proteins with defined amino acid sequences, often not these specific sequences/structures but the resulting overall physicochemical properties (such as charge and hydrophobicity) are the governing factors during mineralization. Indeed, in the case of the magnetite biomineralization proteins rich in acidic amino acids (negative charges) are found to dominate the impact on crystal morphology. Although many biomineralization systems can be mimicked synthetically using additives and templates, achieving control over the nucleation and growth of iron oxides is difficult as they are only sparingly soluble in water (-log(Ksp) = 34-44, typically), and biomimetic experiments generally result in polydisperse products that often do not exceed the superparamagnetic size range (<20 nm).
Here we show that control over the size and sipersibility, and thereby over the properties of magnetite can be achieved in aqueous media through polypeptide additives by controlling the supersaturation and thereby the crystallization kinetics. We have developed a synthesis protocol to controllably produce random co-polypeptides to rule out any structural effects, and created a library of these copolymers with varying monomer contents to study their compositional effects. We employ this library in s specifically designed co-precipitation methods, show that a pathway via a poorly ordered precursor material enables a more gradual evolution of the supersaturation, enabling crystals with sizes similar to those encountered in magnetotactic bacteria.

As components of biomaterials, recombinant proteins provide structural and functional specificity, controlled composition, and intrinsic biocompatibility. However, recombinant proteins are often lacking in terms of scalability, durability, and utility outside the biological milieu. We are engineering proteins to address these limitations. For example, the protein crustacyanin is a component of crustacean carapace responsible for pigmentation. Crustacyanin and similar carotenoid-binding proteins have materials applications in food science, artificial coloration, antioxidant biosensing, thermochromics inks, and light- and energy-harvesting. We explore whether carotenoprotein production and isolation is improved upon fusion to an elastin-like polymer. Toward the development of tunable, protein-based, color-changing “smart” materials, we test the hypothesis that in the presence of stimuli-responsive elastin-like polymers, crustacyanin can experience environmental change sufficient to induce reversible changes in bound carotenoid absorption. Other recent optoelectronic/materials applications of elastin-like polymer materials will also be presented.

In 1804, Theodore von Grotthuss proposed a mechanism for proton (H⁺) transport between hydrogen bonded water molecules that involves the exchange of a covalent bond between H and O with a hydrogen bond. This mechanism also supports the transport of OH^- as a proton hole and describes proton transport in intramembrane proton channels. Inspired by the Grotthuss mechanism and its similarity to electron and hole transport in semiconductors, we have developed semiconductor type devices that are able to control and monitor a current of H⁺ as well as OH^- in hydrated biopolymers derived from shrimp and squid. I will present the integration of these devices with enzymes and ion channels. I will also discuss recent data on biopolymers extracted from fish sensory organs.

Cephalopods (squid, octopuses, and cuttlefish) are known as the chameleons of the sea - they can alter their skin&’s coloration, patterning, and texture to blend into the surrounding environment. These remarkable capabilities are enabled by the unique morphology of cephalopod skin, as well as by its constituent proteins and nanoscale structures. I will discuss our work on new types of photonic and protonic devices fabricated from cephalopod-derived materials. Our findings may hold implications not only for the next generation of stealth and bioelectronics technologies, but also for gaining insight into the mechanisms that underpin cephalopods&’ camouflage abilities.

Abasic sites in DNA are of interest due to their prevalence as both naturally-forming defects and as synthetic inclusions for biosensing purposes. The electronic impact of these defects in DNA sensor and device configurations has yet to be clarified. Here we report the effect of an abasic site on the rate and yield of charge transport relative to undamaged and mismatch-containing duplexes through surface-bound DNA electrochemistry on multiplexed chips. This approach enables direct temperature-controlled comparison under biologically relevant conditions with redundancy and ensures identical assembly conditions of each sequence. Transport yield through the abasic site monolayer strongly increases with temperature, but the yield relative to an undamaged monolayer decreases with temperature. This is opposite to the increasing relative yield with temperature from a mismatched base pair, and these effects are accounted for by the unique structural impact of each defect. Notably, the effect of the abasic site is nearly doubled when heated from room temperature to 37 °C. The rate of transport is largely unaffected by the abasic site, showing Arrhenius-type behavior with an activation energy of ~300 meV. Detailed investigation of the electronic impact of an abasic site elucidates the electrical impact of these biologically spontaneous defects and aids in the continued development of electrical and electrochemical biological sensors for DNA damage and DNA damage repair.

One-dimensional organic nanowires have emerged as idealized model systems for investigating charge transport mechanisms at molecular length scales. However, there are significant difficulties associated with the synthesis and electrical characterization of well-defined organic nanowires. By drawing inspiration from oligonucleotide synthesis, we have developed a facile strategy for the assembly of organic semiconductor building blocks in predetermined arrangements on a DNA-like backbone. Not only can the resulting constructs be purified/processed under partially aqueous conditions via known biochemical techniques, but also they feature many of the advantages of standard oligonucleotides, including a well-defined length, geometry, and sequence context. We have self-assembled monolayers of our nanowires on gold substrates and investigated their charge transport properties with electrochemical techniques. Our findings hold significance both for fundamentally understanding nanoscale charge transport phenomena and for the development of new types of biological and molecular electronic devices.

Peripheral nerves are tubular structures carrying parallel axons bundled in fascicules. Following nerve injury, the peripheral nervous system has the ability to regenerate because of a permissive environment and activation of the intrinsic growth capacity of neurons. Yet functional recovery is rarely achieved, especially over long gaps.
In this context, we are developing single and multi-lumen nerve implants based on soft elastomers, biodegradable gels and compliant electrodes to (1) support and promote robust regeneration of axons, (2) understand how peripheral neurons interact with their immediate physical environment, and (3) communicate reliably with the regenerating axons.
Conduits filled with fast-degradable fibrin-laminin gels that encapsulate adipose-derived stem cells support improved and robust outgrowth of neurites. Implant&’s surfaces decorated with dense arrays of soft PDMS micropillars promote alignment of growing neurites. Soft thin-metal film electrodes embedded in the PDMS microchannel implant provide an efficient recording interface with the regenerating neurons.
Combined into a unique implant, these bioinspired designs offer an exciting avenue for efficient regenerative nerve prosthesis.

Leather is a material with long history. Due to its unique properties it is widely used in numerous consumer applications such as apparel, shoe, furniture, automotive and many others. Leather is the byproduct of the meat industry. As such it requires the raising, transporting and slaughtering of animals, which carries a large and unsustainable environmental footprint. In addition to the environmental and resource challenges of the livestock industry, leather presents additional challenges to manufacturers. Due to variations in size and shape and imperfections from the rough lives of animals, only a fraction of available hide material can be used as premium leather. The material that is used in products varies widely in quality from hide to hide. Manufacturers must deal with variability in leather thickness, stretch, color, texture, strength, and other significant properties.
We describe the development of bio-leather, a novel biomaterial. The basic concept underlying bio-leather is that the complex anatomical skin of the animal is not required to produce a material with leather-like properties rather what is needed is the collagen matrix, the major component of skin and the cornerstone of leather. Another novelty of our approach is that it uses established principles of tissue engineering beyond regenerative medicine, its traditional domain of applicability. Specifically, our bio-leather is derived from carefully selected and engineered collagen secreting mammalian cell lines, sourced from live animals. We build a three dimensionally organized collagen matrix, the analogue of the hide of live animals. This tissue is subsequently tanned to prepare it for further processing. Tanning of our material requires the development a novel leather chemistry technologies as historical methods do not apply.
An engineered and sustainable leather would solve many of the problems manufacturers face when using animal-derived leather. The material could be grown to the desired size and shape, optimized for the efficient manufacture of final products. Bioengineered leather can be tuned to the exact physical properties desired by a manufacturer, and could be made in consistent quality. With engineered bio-leather, manufacturers would discard less material as waste, and would be able to produce better and more consistent products. Furthermore, it could be produced at a lower environmental cost and in a no-kill way, without the need to slaughter animals.
Finally, due to its unique method of fabrication, bio-leather could be combined with advances in industries such as electronics and photonics. This would allow, in particular, for built-in biological functionalities into a comfortable wearable material.

Membrane transport is critical to cellular functionality, which makes membrane proteins potentially important components of a bioelectronic toolkit. Integrating membrane proteins with nanoelectronics requires a versatile biocompatible matrix that can preserve and enhance the protein functionality. We accomplish this task by using hierarchical assembly of lipid molecules and membrane proteins onto silicon nanowire transistor to create 1-D bilayer devices—a bioelectronic platform that can convert proton and ion transport events into electrical signals. In this presentation I will discuss several examples of bioelectronic devices that use passive ion channels and active ATP-driven and light-driven pumps, as well as biological modifiers to drive and regulate electronic functionality. I will also talk about our ongoing efforts to create more robust and scalable bioelectronic platforms and membrane transporters.

Introduction: Lactate is a well-known biomolecule which is produced as a result of anaerobic respiration of various organisms. As it is now known that stem cells mainly use anaerobic respiration to produce energy source ^[1], it is meaningful to develop lactate sensor which can be applied to monitor cellular respiration of stem cells in real time manner. Phenylboronic acid (PBA) has an ability to bind to diol compounds, such as lactate and saccharides, which induce negative charge on the boron atom of PBA ^[2]. Our group has been detected the charge changes derived from PBA-sugar equilibrium using field effect transistor (FET), whose extended gate was modified with PBA self-assembly monolayers ^[3]. In this research, we have investigated the possibility of specific detection of lactate by use of FET combined with lactate template molecular imprinted polymer (MIP) gel containing PBA molecule.
Method: MIP gel coated-gate FET with lactate template was prepared by following procedure. First, Au/Ti was sputtered on the glass substrate, and the plastic ring was glued on the surface. After washing Au surface with piranha/ozone, 10 uL of monomer solution with initiator was dropped on it and spin coated. Polymerization was initiated by irradiation of UV light. Finally, polymer was washed with HCl/methanol solution to extract the template molecule, lactate. In the FET analysis, surface potential change was monitored by use of FET real-time monitoring system when the sample solutions (lactate and glucose) were added to the solution system of MIP gel coated-gate FET with lactate template, which was equilibrated with phosphate buffer solution (pH 7).
Result and Future Plan: When lactate was introduced onto the MIP gel coated-gate FET with lactate template, the surface potential shifted clearly in the negative direction based on the increase of negatively charged PBA derived from binding to lactate. Moreover, the decrease of the surface potential in the FET could be observed depending on the concentration of lactate addition, and we have confirmed even at lower concentration of 10 uM, which would be appropriate for sensing in human blood. Thus, we succeeded to develop sensor specific to lactate to some extent. On the other hand, the signal from glucose was controlled by MIP gel interface, even though surface potential decreased for addition of glucose. In the future, we hope to improve further the specificity of the sensor and apply it for sensing living cells.
References
[1] T. Suda, K. Takubo, G. L. Semenza, Cell Stem Cell 9, 298-310 (2011).
[2] F. K. Sartain, X. Yang, C. R. Lowe, Chem. Eur. J.14, 4060 - 4067 (2008).
[3] T. Kajisa, T. Sakata, ChemElectroChem1, 1647 - 1655 (2014).

Films organized at the molecular level are useful systems for a variety of applications since their properties can be easily controlled and manipulated. The Langmuir-Blodgett (LB) technique is a well-established way to produce ultrathin films with the possibility to stack layers transferred from monomolecular films organized at the air-water interface. In this sense, it is growing the interest for the fabrication of LB films produced with biological molecules, such as enzymes, lipids and polysaccharides, originating a type of systems classified as a bioinspired system. In this present work, we used algal exopolysaccharides (EPS) from Cryptomonas sp to serve as an intermediate matrix for the adsorption of enzymes on lipid monolayers at the air-water interface. Firstly, the lipid dioctadecyldimethylammonium bromide (DODAB) was spread on the top of EPS aqueous solutions. After that, the enzyme urease was inserted below the DODAB monolayer, allowing for its incorporation to the interface. The urease was then co-adsorbed with EPS on the lipid monolayer, and the three-component film was compressed by mobile barriers until the collapse of the monolayer. Surface pressure-area isotherms and Polarization modulation reflection-absorption spectroscopy (PM-IRRAS) showed that the presence of EPS enhanced urease adsorption. By keeping the surface pressure of 30 mN/m constant, the film was then transferred to the air-water interface to solid supports. PM-IRRAS spectroscopy showed that the secondary structure of the enzyme kept intact, and atomic force microscopy showed that the morphology of the lipid films was significantly affected with the presence of EPS and urease, with the formation of some aggregates. The enzyme activity of urease was then essayed with UV-vis spectroscopy with several molecular architectures for the LB films, trying all possible combinations involving urease, EPS and DODAB. The results showed that the presence of EPS enhanced the enzyme activity of urease, which was higher than in solution. Enzyme activity was also essayed for urease aggregated with EPS in the aqueous subphase for DODAB monolayer, and the results showed a lower value than for urease without EPS in the aqueous subphase for the same lipid monolayer. These results then indicated that the best molecular accommodation for urease is when it is present in a polysaccharide-lipid surface rather than interacting with EPS in solution. The results also showed a good stability and conservation of the enzyme activity for at least two months. The results of this work, as a proof-of-concept experiment, seem therefore important for the fabrication of urease sensors with easy control of the molecular architecture.
Acknowledgements: FAPESP and CNPq

Charge transport in double-stranded DNA, is involved in many basic chemical and biological processes, and its understanding is critical if they are to be used in electronic devices. This important phenomenon is often described as either coherent tunnelling over a short distance or incoherent hopping over a long distance. Here, we show evidence of an intermediate regime where coherent and incoherent processes coexist in double-stranded DNA. We measure charge transport in single DNA molecules bridged to two electrodes as a function of DNA sequence and length. Generally the resistance of DNA increases linearly with length, as expected for incoherent hopping. However, a periodic oscillation is superimposed on the linear length dependence for DNA sequences with stacked GC base pairs, indicating a partial coherent transport. Our calculations of the molecular orbital distribution also indicates a strong delocalization among the stacked Guanies bases. Finally, by fittting the data with Buttiker's partially coherent in hopping model, we obtained a coherent length of ~0.56 nm, about two base pairs long.

DNA microarrays are a powerful and universal analytical tool in biological/medical research and diagnostics. However, the read-out approach is still relying on fluorescence markers and infrastructures in the form of fluorescence microscopes and/or fluorescence scanners. Here we propose a novel approach to facilitate a purely optical read-out DNA detection by combining enzymatic DNA polymerization^{1, 2} with the diffracting grating principle³. The basic idea is to exploit the strong dependence of the diffraction intensity on the grating height. By patterning oligonucleotide probe strands which get amplified by DNA polymerization only after a target strand hybridizes with the latent grating structure, the grating height increases which will boost the diffraction intensity.
The scheme of our approach is described as follows:(I) a grating of probe oligonucleotide, immobilized at their 3&’ termini, is patterned. The resulting grating is so thin that it shows only minor diffraction intensity. (II) When a matching target DNA strand hybridizes onto the probe oligonucleotide grating, it intercalates, but position the 3&’ terminus of the target strand away from the substrate surface, where it is accessible to serve as an initiator for the subsequent enzymatic DNA polymerization. This hybridized strand is still latent in its diffraction activity, since the hybridization does not significantly alter the grating&’s height. (III) When the grating is incubated with TdT (terminal deoxynucleotidyl transferase) enzyme in the presence of mononucleotides, TdT attaches selectively only to the hybridized gratings with accessible 3&’ termini, and extends the oligonucleotide strands. (IV) This conditional DNA polymerization increase the grating height which in turn amplifies the optical diffraction capability of the grating.
To elucidate the efficacy of our concept, DNA polymerization from a simple oligonucleotide grating was performed. A 600nm period of patterned 5&’ thiol-modified (dA)₂₀ on gold film was fabricated by means of E-beam lithography and incubated with TdT enzyme in the presence of dATP. As a result of enzymatic extension of the oligonucleotide from 3&’ termini, thickness of the oligonucleotide layer increased in the order of 10nm, and incident angle dependent color change, which stem from the light diffraction by the grown grating structure, was confirmed even by visual observation.
Dependence of hybridization/sensing efficiency and optical diffraction activity on probe oligonucleotide density will also be demonstrated.
References:
1. Chow, D. C.; Lee, W.-K.; Zauscher, S.; Chilkoti, A. J. Am. Chem. Soc.2005, 127, 14122.
2. Tjong, V.; Yu, H.; Hucknall, A.; Rangarajan, S.; Chilkoti, A. Anal. Chem.2011, 83, 5153.
3. Lenhert, S.; Brinkmann, F.; Laue, T.; Walheim, S.; Vannahme, C.; Klinkhammer, S.; Xu, M.; Sekula, S.; Mappes, T.; Schimmel, T.; Fuchs, H. Nat. Nanotechnol.2010, 5, 275.

The use of bio-design concepts is a promising strategy to fabricate materials with properties of great scientific and technological interest. There are numerous examples of materials obtained by employing concepts of biomimetics, engineering and bio-inspired and biotemplates that has gained prominence position in the chemistry of the materials, especially when these structured systems are employed in DNA, bacteria or fungi. A variety available of biological structures enables several innovative alternatives to overcome the limitations of conventional synthesis methods. In this context, the fusion of biotechnology with materials chemistry has benefited several areas of strategic technologies such as catalysis, health and sensor development. Thus, this work propose the use of design concept of biomimetic to establish a protocol to fabricate self-organized systems of metal nanoparticles on surfaces with the composition, structure and morphology controlled in the shape of plates, wires, tubes using among other metals, ceramics and polymers. Biomolecules were produced by fungi Penicillium brasilianum, which were added in systems containing surfaces to be coated with metal nanoparticles. Biomolecules act as an agent to induce self-assembly of metal nanoparticles on the surfaces of silicon wafers. The first tests consisted of silicon wafers suspended by a thread in a system containing gold nanoparticles and hyphae of the fungus for a period of 5 days. The experiment indicated that the metabolites produced by the fungi and released in the middle act directly on the stability of the nanoparticles in the colloidal suspension, causing deposition on the available surfaces, are organic or inorganic. The deposition of the nanoparticles of the nanoparticle layer resulting in a self-assembly effect induced by micellar biomolecules produced by fungi. The presence of metabolites produced by the fungi colloidal medium directly affects the stability of the nanoparticles, favoring the formation of successive layers of nanoparticles. The silicon wafers have a surface coated with gold nanoparticles in the form of spheroidal and the surfaces coating variable thickness between 25 nm to 200 nm.

The use of biotemplates concepts is a promising strategy for obtainment materials with properties of great scientific and technological interest. Biotechnology and supramolecular systems usually vary from a few nanometers up to no more than any micrometer, which facilitates their combination for the manufacture of large heterostructures morphological and functional complexity. Inorganic nanoparticles are particularly useful to be used as building blocks of hybrid self-organized systems can be synthesized in large quantities. In this work is proposed use design concept of biotemplate with mycelial fungi Penicillium brasilianum by the fabrication of nanostructured materials in the form meshed network tridimensional microtubes. In first step were prepared microtube by self-organized of metal nanoparticles with 20 nm synthetized by Citrate Methold on surfaces of hyphae fungal. The 2 g of mycelial mass were auditioned in 100 mL of colloidal gold 1,0 mmolL^-1 for 20 days. The second step was lyophilization of microtubes of gold a consolidated wire after heated under oxygen flow at 400 ^oC for 2h and analyzed by SEM and Electrical characterization. Initial examination of images SEM showed substantial changes in the morphology of the surface when compared to original hybrid material before annealing. Instead of a uniform layer of well-characterized gold nanoparticles, it is possible to observe a rough surface of consolidated wires in substitution of the original microtubes. The coalesced nanoparticles, forming a rough surface wires consolidated instead of original microtubes. The resulting material has preserved the original memory biotemplate morphology, forming a surface having high surface area and similar to a sponge with a high mechanical strength and potential catalytic activity The nanostructured materials in the form meshed network have microtube with mean diameter calculated (0,58 mu;m) is almost half of the value calculated for gold microtube (1,24 mu;m) but with approximately the same distribution. Probable, one or more microtubes fused to form a thicker wire, which can be observed by the twisted shape of the gold microwires. Electrical characterization of nanostructured materials, showed a typical metal behavior was observed in the electrical resistance, increasing the resistance with the temperature increasing and the ohmic response indicates continuous, metallic connections across the sample. The low resistance is that expected for grain-boundary-dominated transport in a polycrystalline metal.

Polyaniline (PANI) films in the emeraldine salt form deprotonate in physiological media and thus their conductivity is reduced thereby limiting their potential use in the area of regenerative medicine [1, 2]. Therefore a thorough understanding of deprotonation of PANI thin films is vital. In this study, we demonstrate the utilisation of X-ray photoelectron spectroscopy (XPS) to elucidate and quantify the deprotonation of PANI films upon incubation in physiological conditions. Time of flight secondary ion mass spectroscopy (ToF-SIMS) served as complimentary technique to surface map the presence of anion dopant both before and post incubation. PANI was doped chemically by a small acid molecules; p-toluene sulfonic acid (pTSA) and camphor sulfonic acid (CSA) and thin films fabricated using the spin coating technique. This was followed by incubation in phosphate buffered saline (PBS), at pH 7.4 for 24 hours. Changes in the protonation level of these films were assessed by careful analysis of the N 1s core line spectra, revealing the doping level at the surface if the PANI films. The level of doping was determined by the area ratio of positively charged nitrogen at higher binding energy (401 eV and 402 eV) to the total N 1s spectra. PANI films were found to de-dope as this ratio decreased from 22.5% to 13.3% for pTSA and 29.2% to 18.4% for CSA after 24 hours. This suggests that the dopant bound to the backbone of PANI at fabrication leaches out. To confirm that the decrease in the protonation level is related to the loss of the dopant, the sulfur content of the films was monitored by XPS and its ratio to nitrogen (S 2p/N 1s) was quantified. The ratio decreased as incubation time increased supporting the reduction in the level of doping observed from the N 1s spectra. De-doping of PANI films was further confirmed by the depletion of the dopant fragment (-SO₃^-) indicated by atomic distribution in ToF-SIMS images. This study shows that XPS and ToF-SIMS could be successfully utilised as surface tools to elucidate the deprotonation of PANI films following incubation in physiological conditions [3]. We are currently exploring the improvement of PANI's biostability to retain its functionality through other doping methods.
References
[1] El-Said WA, Yea C-H, Choi J-W, Kwon I-K. Ultrathin polyaniline film coated on an indium-tin oxide cell-based chip for study of anticancer effect. Thin Solid Films. 2009;518:661-7.
[2] Song Y, Lv H, Yang C, Xiao H, Chen X, Zhu X, Li D. Enhanced electroactivity at physiological pH for polyaniline in three-dimensional titanium oxide nanotube matrix Physical Chemistry Chemical Physics. 2014;16:15796-9.
[3] Mahat MM, Mawad D, Nelson GW, Fearn S, Palgrave RG, Payne DJ, Stevens MM. Elucidating the deprotonation of polyaniline films by X-ray photoelectron spectroscopy. Journal of Materials Chemistry C accepted (2015).DOI: 10.1039/C5TC01038A

An Electrolyte-Gated Organic Field-Effect Transistor (EGOFET) can be used as a gas sensor¹ or a biosensor² when a solid/liquid electrolyte or a biopolymer³ is used as a gating medium. The formation of a Debye-Helmholtz double layer, resulting in a capacitance of few mu;F cm^-2, permits sub-volt operation of these devices. Previous studies have demonstrated that the recognition element can be immobilized either onto² the organic semiconductor (OS) or by functionalizing the metal top gate⁴.
In this work we report on the use of a thiol self-assembled monolayer (SAM) for anchoring the bio-receptor onto the gold gate. AFM measurements confirmed the successful bio-functionalization of the gold gate. As a proof of principle the proposed architecture was afterwards used as sensing device for the detection of various concentrations of streptavidin in phosphate buffer solution.
1. Dumitru, L. M.; Manoli, K.; Magliulo, M.; Palazzo, G.; Torsi, L., Low-voltage solid electrolyte-gated OFETs for gas sensing applications. Microelectronics Journal 2014,45 (12), 1679-1683.
2. Magliulo, M.; Mallardi, A.; Mulla, M. Y.; Cotrone, S.; Pistillo, B. R.; Favia, P.; Vikholm#8208;Lundin, I.; Palazzo, G.; Torsi, L., Electrolyte#8208;Gated Organic Field#8208;Effect Transistor Sensors Based on Supported Biotinylated Phospholipid Bilayer. Advanced Materials 2013,25 (14), 2090-2094.
3. Dumitru, L.; Manoli, K.; Magliulo, M.; Ligonzo, T.; Palazzo, G.; Torsi, L., A hydrogel capsule as gate dielectric in flexible organic field-effect transistors. APL Materials 2015,3 (1), 014904.
4. Casalini, S.; Leonardi, F.; Cramer, T.; Biscarini, F., Organic field-effect transistor for label-free dopamine sensing. Organic Electronics 2013,14 (1), 156-163.

Label free, disposable, low cost and printable biosensors are of great interest for fast and cheap diagnosis of diseases. In this direction, organic field effect transistors based bio-electronics, capable of mass fabrication on flexible substrates are widely investigated. Specifically, electrolyte gated field-effect transistors (EGOFETs) are very promising for bio-sensing applications due to their low-voltage operation in aqueous media and high stability of performance in physiologically relevant electrolyte environments such as Phosphate buffered saline (PBS).[1,2] Sensors based on the principle of field effect transduction (FET) offer an advantage of high sensitivity and controlled operation of the device.[3] But enhancing selectivity of such biosensors demands integration of bio-recognition elements at the electrolyte/transducer interface. This can be achieved by surface bio-functionalization of organic semiconductor active layer or electrodes.[4,2] However, modification of the active layer is undesirable because it adversely affects the electronic properties of the semiconductor, consequently degrades device performance. Alternatively, modification of gate electrode by immobilizing bio-recognition element offers ease of fabrication process while maintaining the optimum electrical performance. Moreover, functionalization of gate electrode allows detecting of subtle variations in capacitance at electrolyte/electrode interface, hence enhancement in the sensitivity can be achieved.[5]
Bio-electronic sensor based on Anti-CRP functionalized gate electrode of EGOFET device is herein proposed for the detection of C-reactive protein (CRP). C-reactive protein is relevant to heart disorders; therefore selective detection of CRP is vital for the diagnosis of cardiovascular diseases. EGOFET device fabricated on flexible polyimde substrate was used as transducer. While Anti-CRP antibody was immobilized on detached flexible gold gate electrode using self-assembled monolayers of thiolated molecules bearing carboxylic moieties. Elemental composition after functionalization of gate electrode was determined by X- ray photo-electron spectroscopy (XPS). Surface plasmon resonance (SPR) technique was used to optimize the bio-functionalization process. CRP concentrations starting from sub pico-molar range were detected successfully. Such EGOFET based bio-electronic devices should open new doors for printed, low cost, highly sensitive label free biosensors to detect clinically relevant analytes.
[1] L. Kergoat et al. Adv. Mater., 2010, 22, 2565-9.
[2] M. Magliulo et al. Adv. Mater., 2013, 25, 2090-4.
[3] L. Torsi et al. Nat. Mater., 2008, 7, 412-7.
[4] S. Casalini et al. Org. Electron., 2013, 14, 156-163.
[5] M. Y. Mulla Nat. Commun., 2015, 6, 6010.

Cephalopods are well known for their ability to camouflage to their surroundings within millisecond time scales. One important feature of this fast camouflaging process is the organization of their optical organs. For instance, the longfin inshore squid Loligo pealeii contains organized layers with iridophore reflective organs located below chromatophores, which are pigmented organs that can change their size to filter light. While it is known that chromatophores contain nanoscale granules that contribute to the range in visible color displayed along the L. pealeii dermal tissue, the contribution of pigments and proteins within the granules to bulk coloration remains largely unknown. We hypothesize that the chromatophore granules contain high refractive index biomolecules that contribute to the efficient collection and absorption of light within the dermal tissue. To test this hypothesis, we isolated and purified pigments and proteins extracted from the granules using both acidic and basic conditions. Refractive indices of the soluble extracts were measured with an Abbe refractometer at 589 nm in triplicate and with a serial dilution of both conditions. Our data suggests that even though the refractive index of the soluble pigments vary as a function of extraction procedure, they maintain values greater than 1.5, which is a unique feature for biological materials. This high refractive index suggests that light is refracted closer to the normal of the surface of the skin, elucidating a potential mechanism for the efficient collection and absorption of light within the dermal tissue.

Immunosensors are making significant contributions in the advancement of field of clinical diagnostics by providing applications which are faster, reliable and sensitive. Basically immunosensors combines an immobilized immunological receptor utilized for target analyte detection with a transducer which converts the biological interaction into a measurable signal. The expansion of this area is paralleled with progress in biotechnology, nanotechnology and microfabrication, which contributed in development of better transduction and sensing devices. Whereas in recent times Organic field effects transistors (OFETS) have evolved as ultrasensitive, reproducible and highly responsive sensors. The use of organic semiconductors resulted in enhanced biocompatibility, cost effectiveness and portability to these devices. These advantages fairly justify them as a potential candidate for use as transducers and key sensing element in immunosensors. The current goal is to develop robust electronic ultrasensitive immunosensors capable of detecting low concentration of antibodies in biological fluids. The detection of IgG or IgM immunoglobulins in such samples has clinical relevance especially in the diagnosis of autoimmune and inflammatory diseases. For the immunosensors development, the EGOFET configuration has been selected as chosen approach due to its dual functionalization capabilities along with low voltage and aqueous environment operability. Preliminary results of work being performed for development of organic immunosensing platform will be discussed. The focus area will be results of matrix effect evaluation and on measures taken for reducing the non-specific binding of these P3HT based devices. In future work either the semiconductor surface or gate will be functionalized with antibodies specific for the detection of the target analyte.

Diatoms are a prolific class of single cell photosynthetic algae with microscopic 3D silica shells, called “frustules”, which exhibit highly porous, nanopatterned surfaces with excellent mechanical properties. Upon easy removal of the organic stuff by acidic/oxidative cleaning, the resulting nanostructured biosilica represents a suitable templating material for various applications in photonics, molecular separation, biosensing, and drug delivery.¹
Here we report chemical modification protocols of diatoms frustules leading to natural substrates for bone tissue regeneration. In particular, we have functionalized the nanostructured biosilica of Thalassiosira weissflogii with the cyclic TEMPO (nitroxide 2,6,6-tetramethylpiperidine-N-oxyl) radical, an efficient scavenger of reactive oxygen species (ROS) in biological systems. Drug delivery properties of the hybrid TEMPO-biosilica have been investigated using Ciprofloxacin as antimicrobial drug thoroughly employed for infections of orthopedic or dental implants. The resulting TEMPO-biosilica, combining Ciprofloxacin drug delivery with anti-oxidant properties, has revealed interesting ability as natural substrate for fibroblasts and osteoblast-like cells growth.² This is the first example of frustules-based functional biomaterial reported for tissue regeneration.
[1] Yang W. et al, Analyst, 2011, 136:41-53
[2] S. R. Cicco, D. Vona, E. De Giglio, S. Cometa, M. Mattioli-Belmonte, F. Palumbo, R. Ragni, G.M. Farinola, Chem Plus Chem, 2015,doi: 10.1002/cplu.201402398

The advent of biodegradable and biocompatible materials has inspired a wide-range of environmentally or physiologically benign device architectures fabricated from bio-derived materials. Yet, for such devices to be fabricated on a large scale, readily available biodegradable substrate materials must be sourced and used in conjunction with green surface coatings and solvents, such as shellac or gelatin from aqueous or alcohol solutions. In this presentation, pressure switches, made via ink-jet printing and coating on fully-biodegradable substrates, will be presented. The choice of biodegradable substrate will be explained with experimentally-derived surface energies for several biodegradable roll-to-roll processable foils and solvent solubility parameters for a wide range of green solvents. The effect of surface roughness and methods to mediate these effects will be presented that do not require toxic or non-biodegradable precursors or epoxies. Results will be compared with non-biodegradable substrates and differences will be presented. The application of these findings to other electronic and optoelectronic devices will be discussed with a focus on large-scale fabrication and biodegradability.

The oxygen deprivation to the brain, heart, and peripheral tissues is one of the most important causes of serious illnesses (such as stroke, angina pectoris, heart attack, obesity, diabetes, cancer, autism, Alzheimer's disease), disability, and mortality. In this work, we have monitored the mitochondrial matrix swelling and have investigated interactions of mitochondria with a fluorescent cationic dye rhodamine 123 (Rh 123) evidenced by changes in resonance elastic light scattering (RELS) and fluorescence intensity. The effect of various drugs influencing the potassium ion-channel opening and inner mitochondrial membrane polarization have been analyzed to elucidate the mechanisms of reduced sensitivity of some cells to hypoxia and reperfusion conditions. RELS, fluorescence spectroscopy, as well as the electrochemical and microfluidic techniques designed for capture and analysis of mitochondria and their responses to respiratory modulation agents have been employed in measurements.
Acknowledgements: This research was supported by funding provided by the Grant Sonata No. DEC-2012/05/D/ST4/00320 awarded by the National Science Center and by the Grant Iuventus Plus, No. IP2012058072 awarded by the Polish Ministry of Science and Higher Education

Thin films might be fabricated from aqueous solution by layer-by-layer (LBL) deposition technique for applications in optoelectronic devices based on water soluble electronic materials. In this work, the LBL self-assembled thin films of iron or nickel tetrasulfonated phthalocianines (FeTsPc or NiTsPc) and multiwall carbon nanotubes (MWCNT) with different amounts and number of bilayers were fabricated, in controlled pH, on transparent electrode (ITO) and characterized using spectroscopies (Raman, UV-vis absorption, fluorescence and impedance) and atomic force microscopy (AFM). The structural conformation of MWCNT incorporated in LBL films was analyzed by Raman spectroscopy and the superficial roughness dependence on the LBL thickness films was evaluated from AFM images. The UV-vis analysis results of the LBL FeTsPc/MWCNT and NiTsPc/MWCNT films indicate a linear dependence of absorption intensities with number of layers. No further changes on emission spectra profiles of the films have been verified with increasing of number of bilayer. The AC conductivity properties of both films were measured at 1Hz-10MHz at room temperature showed that the increasing the concentration of MWCNT an increase in the AC conductivity is observed. However, a further increase in the number of bilayers led to a decrease in current due to the increase in film electrical resistance. These results allow us to find the number of bilayer which provides the higher performance for optoelectronic applications, such as photovoltaic devices based on water soluble semiconducting materials.

Organizing gold-nanoparticles (AuNPs) into an ordered two-dimensional array with specified lattice structure is fundamental for making metamaterials with desirable properties. A nascent approach is to combine bio-mimetic strategies of self-assembly with 2D organic templates. It has been successfully shown that AuNPs arrays can be formed and tuned at charged interfaces (ref. 1). We employ grazing incidence small-angle x-ray scattering (GISAXS) and reflectivity (XRR) to determine the structure of AuNPs arrays adsorbed from solution to positively charged lipid monolayers. Our analysis of the XRR shows that bare and single-stranded DNA functionalized AuNPs spontaneously adsorb to a positively charged 2D template forming a single layer. The GISAXS analysis, though challenging, reveals different short-range-order (SRO) packing for bare and DNA functionalized AuNPs. We also discuss the effect of introducing simple salt (NaCl) on the adsorbed AuNPs to the template.
Reference:
1. S. Srivastava, et al. Tunable Nanoparticle Arrays at Charged Interfaces. ACS nano, vol. 8, pp. 9857-9866.

Interfacing electronic devices with biological systems for clinical therapeutics has been of interest for many decades now. Traditionally, devices for such applications have involved the use of mechanical or chemical tissue adhesives and stimulators with bulky and rigid designs. Here, we propose to use naturally forming cellular adhesions to interface silicon-based stimulators with target cells and tissues. More specifically, we demonstrate that primary rat neonatal cardiomyocytes can be cultured onto a polymeric grid and can be electrically stimulated by embedded silicon nanostructures upon light illumination. We propose that this semiconductor-cell hybrid device can be used to promote gap junction formation with localized regions of rat heart tissue and modulate electrical conduction throughout the heart upon optical stimulation. These findings can provide us with a platform to optimize therapeutic strategies for patients who suffer from cardiac arrhythmias.

Lipid photo-oxidation is a natural outcome of life under oxygen and essential for Photodynamic Therapy of cancer tissues.¹ Hydroperoxidation, a prominent pathway for lipid oxidation, results in the insertion of the organic hydroperoxide group OOH at the unsaturated bond site.² At the molecular level, the increased hydrophilicity of the lipid chains carrying the OOH groups changes the statistical distribution of chain conformations and leads noticeably to the increase of the area per lipid. Degree of membrane oxidation, and the associated changes in membrane properties such as membrane shape, elasticity or permeability can thus be monitored by a measure of membrane area increase. Here we evaluate the membrane area increase as an outcome of the oxidation induced by the photosensitizer erythrosin B. The latter is studied in biological membrane mimetic systems based on Langmuir monolayers and giant unilamellar vesicles (GUVs). In addition to the usual measurements of surface pressure, the Langmuir films is combined with polarization-modulated infrared reflection adsorption spectroscopy (PM-IRRAS) to provide information about mechanisms of the lipid membrane oxidation at the molecular level. Complementary, the microscopic effects of oxidation is observed in GUVs and characterized by fluorescence and confocal microscopy.
1. B. N. Ames, M. K. Shigenaga and T. M. Hagen, Proceedings of the National Academy of Sciences of the United States of America, 1993, 90, 7915-7922
2. W. Caetano, P. S. Haddad, R. Itri, D. Severino, V. C. Vieira, M. S. Baptista, A. P. Schroder and C. M. Marques, Langmuir, 2007, 23, 1307-1314.
6. O. Mertins, Isabel O. L. Bacellar, F. Thalmann, Carlos M. Marques, Maurício S. Baptista and R. Itri, Biophysical Journal, 2014, 106, 162-171.

Among various materials utilized in resistive switching memories, an increasing attention has been given to the organic molecules due to their flexibility, transparency, scalability, and compatibility with different substrates. Biocompatible natural polymers are the most attractive organic materials for switching layer of ReRAMs because of their natural abundance as well as environmental benignity.
This work is an attempt to fabricate emerging nonvolatile memory devices to get advantage of solution process in a simple metal/insulator/metal structure. We demonstrate fabrication of a solution-assisted natural polymer-based memory device dependent upon resistive switching effect integrated into a crossbar array.
An Ag-doped chitosan solid polymer electrolyte was used as the resistive switching layer which was sandwiched between active and inert electrodes to make an Ag/Ag-doped chitosan/Pt structure. The fabricated ReRAM devices showed bipolar switching behavior according to the applied bias polarities.
Reproducible and reliable resistance changes from high-resistance state to low-resistance state or vice versa were obtained. Additionally, the reliability of the chitosan-based nonvolatile device was confirmed by measuring the data retention. The memory device based on naturally-abundant material has promisingly satisfied the nonvolatile memory functional requirements. A comparable resistive switching behavior was also achieved with flexible memory devices which facilitates the use of proposed ReRAM as a flexible and biocompatible nanoelectronic system.
Detailed fabrication and characterization of the resistive memory devices will be discussed in this presentation.

The use of conjugated polymers as transducers in enzymatic biosensors is one of the fastest growing applications in recent years due to its electrical, electrochemical and optical properties in addition to the advantages related to the diversity and availability of monomers and conjugated polymers, allowing for the manufacture of a wide range of sensors with a large selectivity.¹ Langmuir-Blodgett (LB) films allow for the immobilization of enzymes in well-defined and organized structures, resulting in a minimized loss of activity of the immobilized biomolecule.² In this work, Langmuir-Blodgett films (LB) films were prepared with poly(9,9-dioctylfluorene)-co-thiophene (PF) (synthesized via the Suzuki reaction) and the enzyme urease, which was co-immobilized in order to produce highly stable ordered organic films as thick as nine layers. The films were characterized by PM-IRRAS (polarization modulation reflection-absorption spectroscopy), which showed the main bands related to the PF and to the immobilized. Fluorescence spectroscopy of the films showed photoluminescence related to the copolymer and to the enzyme. The enzyme activity of the LB films with 5, 7 and 9 layers was evaluated according to the methodology proposed by Caseli et al.³ The results showed that as the number of deposited layers increased, the films were more uniform and had a higher catalytic activity, which make these films promising to be applied as reliable and robust urea biosensors.
SIQUEIRA JR., J. R. et al. Immobilization of biomolecules on nanosctructured films for biosensing, Biosensors and Biolectronics, v. 25, p. 1254-1263, 2010.
ZANON, N. C. N.; OLIVEIRA, O. N. Caseli L. Immbolization of uricase enzyme in Langmuir and Langmuir-Blodgett #64257;lms of fatty acids: Possible use as a uric acid sensor. Journal of Colloid and Interface Science, v. 373, p. 69-74, 2012.
Caseli, L.; Crespilho, F. N.; Nobre, T. M.; Zaniquelli, M. E. D.; Zucolotto, V.; Oliveira Jr, O. N. Using phospholipid Langmuir and Langmuir-Blodgett films as matrix for urease immobilization. Journal of colloid and interface science, v. 319, n. 1, p. 100-108, 2008.

Cells as a natural material are pre-fabricated templates that have a micron scale size and 3-dimensional shape. With an aqueous interior and semi-permeable cell wall they also represent a mechanically soft and compressible material. Critically, a yeast cell represents a template that is simple and easy to replicate in large volumes with minimal intervention. We present the direct interfacing of the cells with nanomaterials to make simple structured devices with additional characteristics. For photo responsive devices and photo detectors, the accessible area for photo excitation and also the contact area between the photosensitive material and the electrodes are critical characteristics for efficient function. The integration of the yeast cell&’s intrinsic topographical characteristics into such devices provides an avenue for improving these parameters.
As a micron scale fluid-filled construct, yeast cells can be integrated into devices and materials as an avenue to improve mechanical properties. We encapsulate yeast cells in a layer of graphene oxide and integrate them into and onto large area thin graphene oxide films. Encapsulated yeast cells in these materials enhance mechanical properties as they represent a barrier for crack propagation and a resistive force against compressive and tensile stresses. We are also able to grow n-type Zinc Oxide nanorods and nanowires for solar applications, with topographically enhanced properties, on both single cell and thin film devices.

The interaction of proteins with nanostructures is governed by the properties of the nanoparticles (e.g., size, shape, and capping agents), the characteristics of protein (e.g., pKa, charge distribution, hydrophilicity/hydrophobicity, solvation, presence and accessibility of specific amino acids with affinity to the surface of nanostructures), and the medium properties (e.g., pH, ionic strength and polarity) that determine the degree of ionization of the functional groups in the protein on the nanoparticle surface. There are several aspects of the bio/nano interface that remain poorly understood and previous studies are often contradictory to one another. In this study, using size-controlled gold nanoparticles as model abiotic system, we investigated the effect of surface curvature on the activity of a model enzyme (horseradish peroxidase) bound on the surface of the nanostructures. The curvature of the nanostructures was found to profoundly influence the activity of the bound enzymes compared to that of the free counterparts. This study improves our understanding of the bio/nano interface and the design of bioinorganic hybrids with synergistic and enhanced properties with applications in biomimetic and bioenabled sensors, energy harvesting structures, optoelectronic components and devices, responsive and autonomous materials.

This talk will discuss a versatile bio-inspired approach leading to hybrid single crystals whose internal structures are controlled at the nano and meso-scale. Single crystals of calcium carbonate are co-precipitated in the presence of organic and inorganic nano-objects functionalised with tailor-made copolymers as a soluble crystal growth agents. High levels of entrapment is achieved generating crystals occluding 10 - 20 vol% of nanoparticles. Influences of surface chemistry/structure, size and shape of the nanoparticles on the incorporation are further investigated. A range of techniques including IR spectroscopy, high resolution powder XRD and high resolution TEM are used to compare the structures of these crystals with calcite single crystals of geological and biogenic origin. These results therefore demonstrate that the biomimetic strategy of creating composite crystals by occlusion of macromolecules or fibres can be successfully applied to synthetic crystal growth, yielding crystals with selected compositions and properties.

Silks are generally defined as protein polymers that are produced naturally by some Lepidoptera larvae such as silkworms, spiders, scorpions, and flies. Silkworm silk and spider silk are the most studied and widely used and are excellent materials for biomedical applications such as drug delivery and tissue engineering because of their biocompatibility, biodegradability, and extraordinary mechanical properties. Spider silks are known as the strongest and toughest natural fibers, possessing unrivalled extensibility and high tensile strength. Silkworm silk has been used as suture material for centuries and recently has gained considerable attention as a biomaterial with various medical applications due to its slow rate of degradation in vivo and its ability to be fabricated into multiple types of materials such as fibers, films, gels, and foams. To extend the applications of silk materials, researchers have recently transitioned from focusing on pure silk materials to silk-based nanocomposites. Many nanocomposite materials have been fabricated by combining inorganic materials such as gold, silver, silica, graphene, and carbon nanotubes with silks. Generally, these nanocomposite materials are prepared by in situ synthesis of inorganic nanomaterials or by employing layer-by-layer approaches. Some of the resultant properties of these composite structures may be exploited to develop novel biocompatible devices. In this work, we developed a new method for the preparation of silk-based biocompatible nanocomposite materials. With this method, we are able to dope different kinds of nanostructures into silks including gold nanoparticles, gold nanorod, and iron oxide magnetic nanoparticles very efficiently. The prepared nanocomposite materials are characterized by structural analysis techniques such as solid-state nuclear magnetic resonance (NMR) spectroscopy, Raman spectroscopy and IR spectroscopy. Furthermore, they are demonstrated to show good SERS property, fluorescent property and magnetic property, respectively.

Ionic transistors from organic and biological materials represent an emerging class of devices for bioelectronics applications. Within this context, protonic transistors represent exciting targets for further research and development despite the fact that they have received relatively little attention. Given the ubiquity of proton transport and transfer phenomena, protonic devices represent a natural choice for interfacing rugged traditional electronics and biological systems, facilitating the sensitive transduction of biochemical events into electrical signals. We have recently fabricated and characterized protonic transistors from the cephalopod structural protein reflectin. We have investigated these devices with standard electrical and electrochemical techniques, and our findings indicate performance comparable to the state-of-the-art for protonic transistors. Moreover, we have developed simple strategies for improving the performance of our devices by altering their active layer geometry. Overall, our findings may hold significance for a broad range of biomedical and bioelectrochemical devices.

Vertical organic field effect transistors (VOFETs) can be described as stacked-structures with an active cell on top of a capacitor cell [1] where the source electrode has to be so thin to ensure electrical transparency. The interest of VOFETs is the possibility they offer of short channel thicknesses (in the nm range), low operating voltages, high current outputs and high ON/OFF ratios. On the other hand, electrolyte-gated (EG) transistors permit high current modulations and ON/OFF ratios upon application of low electrical biases (ca 1 V) [2,3]. VOFETs and EG transistors open exciting avenues to explore the fundamentals and exploit the technological potential of biopolymers exhibiting good biocompatibility and biodegradability properties. In particular this is pertinent for the eumelanin biopolymer, whose charge carrier transport properties have been elusive to scientists in the last decades. Eumelanin has peculiar physicochemical properties, such as broad UV-vis absorption, thermoregulation, stable free radical population, ability to bind metal ions [4]. To make a significant step forward in the application of eumelanin in bioelectronics, we fabricated VOFETs and EG transistors based on thin films of eumelanin as the transistor channel. The biopolymer was synthesized following a procedure already reported in the literature [5]. Gold was used for the source and drain electrodes. High surface area carbon was used as the gate electrode to maximize the chances to properly detect charge transport in eumelanin [2,3]. Phosphate-buffered saline was used as electrolyte in EG devices. Preliminary results show a significant current output modulation at low gate voltages (ca 1V) for the VOFETs possibly attributable to short channel distances. EG devices show weaker current modulation in comparison with vertical devices possibly due to excessively high interelectrode distances in planar configuration (about 10 µm vs 100 nm in VOFETs). Results show that the eumelanin has a great potential for bioelectronics and justifies further research efforts.
1- L. Ma, and Y. Yang. Unique architecture and concept for high-performance organic transistors. Appl. Phys. Lett., 2004, 85, 5084-5086.
2- H. Tang, P. Kumar, S. Zhang, Z. Yi, G. Crescenzo, C. Santato, F. Soavi, and F. Cicoira. Conducting polymer transistors making use of activated carbon gate electrodes. ACS Appl. Mater. Interfaces, 2015, 7, 969-973.
3- J. Sayago, X. Meng, F. Quenneville, S. Liang, E. Bourbeau, F. Soavi, F. Cicoira, and C. Santato. Electrolyte-gated polymer thin film transistors making use of ionic liquids and ionic liquid-solvent mixtures. J. Appl. Phys., 2015, 117, 112809.
4- P. Meredith, and T. Sarna. The physical and chemical properties of eumelanin. Pigment Cell Res., 2006, 19, 572-594.
5- E. S. Bronze-Uhle, A. Batagin-Neto, P. H. P. Xavier, N. I. Fernandes, E. R. de Azevedo, and C. F. O. Graeff. Synthesis and characterization of melanin in DMSO. J. Molec. Struct., 2013, 1047, 102-108.

Eumelanins are an important class of the natural pigments with attractive physicochemical properties [1]. Unfortunately, eumelanins are poorly insoluble in several common solvents [1] making challenging the deposition of thin films for device applications. To improve their solubility, eumelanins derivatives have been synthetized using organic solvents such as DMSO (D-eumelanin) by incorporating sulfonate groups (-SO₂CH₃) in the phenolic hydroxyl positions of DHI (5,6-dihydroxyindole) and DHICA (5,6-dihydroxyindole-2-carboxylic acid) eumelanin building blocks [2,3]. To shed light onto the transport properties in D-eumelanin, in view of applications in bioelectronics, we performed a systematic study of the redox processes in D-eumelanin, synthetized at room temperature (RT) and at 100°C, by cyclic voltammetry (CV, using eumelanin on carbon paper as work electrode, platinum wire as the counter electrode, and aqueous ammonium acetate at pH 5.5 as the electrolyte, different cycle numbers and 5, 10, and 50 mV/s scan rates were conducted). Sigma eumelanin was used as our control material. D-eumelanin synthetized at RT and at 100 °C showed an intense oxidation peak 0.4 V with well-defined character and a reduction peak around 0.25 V. After five cycles, a capacitive behavior was dominant. An intense and irreversible oxidation peak, located at about 0.5 V was observed for Sigma eumelanin. The irreversible peak for the Sigma eumelanin has been interpreted as resulting from the covalent coupling of intermediate species forming at the positive electrode interface [4]. The peaks for the D-eumelanins are attributable to the HQ/SQ/Q redox species which exhibited an increased in the reversibility when the scan rate was increased. Raman spectroscopy revealed that there is no significant change in the molecular structure after the CVs except for the soufonate groups and hydroxyls. No significant difference was detected between D-eumelanin synthetized RT and 1000C from the electrochemical and structural point of view. Based on the stability observed upon electrochemical tests, D-eumelanin has a good potential for applications in bioelectronics.
1- P. Meredith, and T. Sarna. The physical and chemical properties of eumelanin. Pigment Cell Res., 2006, 19, 572-594.
2- S. N. Dezidério, C. A. Brunello, M. I. N. da Silva, M. A. Cotta, and C. F. O. Graeff. Thin films of synthetic melanin. Journal of Non-Cryst. Solid, 2004, 338-340, 634-638.
3- E. S. Bronze-Uhle, A. Batagin-Neto, P. H. P. Xavier, N. I. Fernandes, E. R. de Azevedo, and C. F. O. Graeff. Synthesis and characterization of melanin in DMSO. J. Molec. Struct., 2013, 1047, 102-108.
4- J. Wünsche, Y. Deng, P. Kumar, E. Di Mauro, E. Josberger, J. Sayago, A. Pezzella, F. Soavi, F. Cicoira, M. Rolandi, and C. Santato. Protonic and electronic transport in hydrated thin films of the pigment eumelanin. Chem. Mater., 2015, 27, 436-442.

We designed novel peptide Gemini surfactants (PG-surfactants), DKDKC₁₂K and DKDKC₁₂D, which can solubilize Photosystem I (PSI) of Thermosynecoccus elongatus and Photosystem II (PSII) of Thermosynecoccus vulcanus in an aqueous buffer solution. To assess the detailed effects of PG-surfactants on the original supramolecular membrane protein complexes and functions of PSI and PSII, we applied the surfactant exchange method to the isolated PSI and PSII. Spectroscopic properties, light-induced electron transfer activity, and dynamic light scattering measurements showed that PSI and PSII could be solubilized not only with retention of the original supramolecular protein complexes and functions but also without forming aggregates. Furthermore, measurement of the lifetime of light-induced charge-separation state in PSI revealed that both surfactants, especially DKDKC₁₂D, displayed slight improvement against thermal denaturation below 60 °C compared with that using β-DDM. This degree of improvement in thermal resistance still seems low, implying that the peptide moieties did not interact directly with membrane protein surfaces. By conjugating an electron mediator such as methyl viologen (MV²⁺) to DKDKC₁₂K (denoted MV-DKDKC₁₂K), we obtained derivatives that can trap the generated reductive electrons from the light-irradiated PSI. After immobilization onto an indium tin oxide electrode, a cathodic photocurrent from the electrode to the PSI/ MV-DKDKC₁₂K conjugate was observed in response to the interval of light irradiation. These findings indicate that the PG-surfactants DKDKC₁₂K and DKDKC₁₂D provide not only a new class of solubilization surfactants but also insights into designing other derivatives that confer new functions on PSI and PSII.

Introduction
Allergy is one of the closest diseases at the present day which is widely infected and induced by various allergen sources. To find a quicker and more accurate way to detect allergy in clinical test and drug discovery, we focused on type I reaction and considered histamine as one of the main signal source secreted from allergy reaction. In this research, we tried to monitor the allergic reaction of cultivating cells by use of a field effect transistor (FET) and detect histamine specifically by the FET combined with molecular imprinted polymer (MIP) film on the gate surface.
Experiment
Detection of cell allergic reaction by ion sensitive FET (ISFET) 1 × 10⁵/mL of Rat basophilic leukemia (RBL) was cultivated on the gate insulator of ISFET in the culture medium including IgE, and after changing culture medium, antigen was added on the IgE-RBL-based FET. At the same time, β-hexosaminidase activity which is widely used for evaluation of histamine was quantified following the antigen-antibody reaction at the cell membrane.
Specific histamine detection by MIP coated-gate FET Extended gate FET combined with polymer gel was used for specific detection of histamine [1]. MIP gel coated-gate FET with histamine template was fabricated by direct UV polymerization onto the Au gate electrode using monomers, which were consisting of acrylic acid as a main chain, ethylene glycol dimethacrylate as a cross linker, and mixing the target molecule, histamine, dissolved in dimethyl sulfoxide/water. After polymerization, histamine was removed from polymerized MIP film using organic solvent.
Result and future plan
Using the IgE-RBL-based FET, the gate surface potential decreased continuously and specifically in response to the allergen addition. This result indicates that basic compound histamine released by RBL was monitored on the basis of pH changes at the cell/gate interface by the ISFET. Thus, we have recognized the allergic reaction by use of the principle of FET. For specific histamine detection, the MIP coated-gate FET with histamine template showed extensive decrease of gate voltage using the real-time monitoring system when concentration of histamine solution raised from 100 mM to 10 mM. In this study, we have clarified the detection of histamine using the FET biosensor. Additionally, the FET with MIP film may enhance the selectivity of histamine detection, but this result is now under consideration and we need to discuss in the conference.
References
[1] T. Sakata, S. Matsumoto, Y. Nakajima, Y. Miyahara Jpn. J. Appl. Phys. 44, 2860-2863 (2005)

Fast, cost-effective and non-invasive simultaneous monitoring of critical biomarkers in real patient samples is of critical importance for the accurate detection of major metabolic dysregulation and thus the early diagnosis of several diseases. A multianalyte (i.e., glucose, lactate, and cholesterol) biosensing platform based on the amperometric detection of hydrogen peroxide using microfabricated organic electrochemical transistor (OECT) arrays, is herein proposed, aiming to address several key challenges in current biosensing technologies. To this end, high performance OECTs based on the conducting polymer, poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonate), were successfully fabricated to meet the operation demands of high gain as well as stability. The sensitivity and selectivity of the biosensors was further optimized by the electrodeposition of platinum microparticles onto the gate electrode prior to the enzyme immobilization and by adding a permselective layer respectively. These OECT-based metabolite sensors, integrated with a PDMS-based microfluidic platform for the sample distribution, were successfully utilized for non-invasive bioanalyte detection in biological media. The measured amperometric responses of the biosensor exhibited high sensitivity for each metabolite, with controllable linear response range by tuning the enzyme concentration, enabling thus the detection of both high and low abundance analytes in the same sample. These results suggest the viability, versatility and wide-range applicability of the proposed compact electrochemical biosensor for the simultaneous monitoring of key biologically relevant metabolites in vitro.

Point-of-care (POC) biosensors are integrated diagnostic systems employed for the detection of clinically relevant analytes in biological fluids such as blood, urine and saliva. These devices offer the advantage to provide rapid results directly where the information are needed (e.g. patient&’s home, doctor&’s office or emergency room), thus facilitating an earlier diagnosis and a prompt patient&’s treatment. Various technologies have been proposed for the realization of POC biosensors including label-free techniques based on optical, mechanical and electrochemical transducers. However, the existing devices exhibit poor analytical performance and reliable, quantitative and ultrasensitive platform have been not yet commercialized. Electronic biosensors based on organic field-effect transistors (OFETs) are a promising choice for the development of the next generation of POC devices. These biosensors can be combined with integrated electrical circuits, microfluidic systems and wireless technologies. Furthermore, they offer high sensitivity, biocompatibility and possibility to produce all-printed low-cost biosensors in flexible and disposable formats. Among them, electrolyte-gated (EG)-OFETs have been identified as ideal candidates for biosensors development as they operate at low voltages directly in aqueous buffer solutions. Two EGOFET architectures useful for realization of POC devices will be presented. In the first, the biological recognition elements are anchored on the organic semiconductor surface, while in the second the biomolecules are confined on the gate electrode. Using these configurations ultrasensitive label-free immunosensors for the detection of clinically relevant biomarkers such as C-reactive protein (CRP), a specific biomarker of infiammatory and infection diseases, have been developed. The specific features of the proposed EGOFET biosensors as well as their analytical performances will be discussed.
References
[1] L. Torsi, M. Magliulo, K. Manoli, G. Palazzo, Chemical Society Review 42 (2013) 8612-8628.
[2] Maria Magliulo, Mohammad Yusuf Mulla, Kyriaki Manoli, Donato De Tullio, Preethi Seshadri, Gaetano Scamarcio, Gerardo Palazzo, and Luisa Torsi. Ultrasensitive printable biosensors for point-of-care applications. 18 May 2015, SPIE Newsroom. DOI: 10.1117/2.1201504.005961.
[3] M.Y. Mulla, E. Tuccori, M. Magliulo, G. Lattanzi, G. Palazzo, K. Persaud and L. Torsi. Nature Communications 6 (2015) 6010.

Modern advances in biomedical research call for dynamically controllable systems, and the unique attributes of organic bioelectronics make this class of materials particularly interesting. A novel class of biologically compatible devices is thus being created owing to the structural and functional similarities to biological systems. In infection, a progressing bacterial infection can be studied dynamically within the infected organ of a live host, at much higher resolution and on a smaller spatial scale than ever before, and it is now understood that minute changes in the tissue microenvironment are pivotal for the outcome of infections. By merging the fields of infection biology and organic bioelectronics, we develop conducting polymer devices able to sense, modify, and interact with the infected tissue microenvironment in vivo and in vitro. Spatially and temporally controlled biomimetic in vitro systems will greatly aid our molecular understanding of the infection process, thereby providing exciting opportunities for organic bioelectronics in future diagnosis and treatment of infectious diseases.

Organic bioelectronics refers to the coupling of conducting polymer based devices with biological systems, proven repeatedly in the last decade to provide numerous advantages to a wide variety of biomedical applications in terms of sensitivity, specificity and most importantly, bridging of the biotic/abiotic interface. We focus on the unique properties of organic electronic materials that allow easy processing, and flexibility in design as well as chemical tunability, to develop state-of-the-art tools to (1) develop relevant in vitro models by creating more ‘in vivo&’ like environments and (2) monitor cells i.e. for diagnostic purposes following exposure to toxins or pathogens. We have successfully demonstrated the use of the organic electrochemical transistor (OECT) for monitoring in vitro models of the gastrointestinal tract, the kidney and the blood brain barrier. For each application, we attempt to recreate the in vivo conditions through the use of microfluidics, biofunctionalised materials, combinations of different cell types, while simultaneously designing the materials/devices in the most appropriate form factor to suit the model at hand. Our goal is to develop physiologically relevant in vitro models with integrated monitoring systems that obviate the need for animal experimentation in diagnostics, toxicology or drug development. In this presentation, I will focus on new work that we have carried out to increase the sensitivity of our devices for monitoring a broader selection of tissues in vitro, integration of our devices with cells in 3D formats, and finally, inclusion of multi-parameter monitoring by additional functionalities such as metabolite sensing and high resolution optical imaging into our devices.

Light can be a fruitful tool for controlling cell activity, offering high space and time resolution and a virtually infinite number of configuration, free from wiring constrains. Yet there are draw backs, such as light absorption and scattering, hampering delivery into deep tissues, and a fundamental limitation: by and large living cells are transparent. In this talk we will briefly review the strategies for inducing light sensitivity, and then focus our attention onto biotic/abiotic interfaces based on organic semiconductors in contact with living cells. We will show that upon polymer photoexcitation, the cell can be excited by modification of the membrane properties. This approach has been used for developing an artificial retina implant. Most recent results on the testing in vivo will briefly be reported. As an alternative to the bulk device we are exploring the possibility to inject particles in the cell. Preliminary studies on this approach will be presented, aimed at identifying best candidates in terms of bio compatibility and functionality.

The blood brain barrier (BBB) consists of a layer of endothelial cells that maintains the brain microenvironment, and these endothelial cells are connected to each other by a network of tight junctions. Matrix metalloproteinases (MMPs) and protein tyrosine phosphate (PTP) inhibition disrupt occludin tight junctional proteins critical for the proper function of the BBB. In this work, we investigated the effect of phenylarsine oxide (PAO), a PTP inhibitor and MMP activator on the occludin network of Madine Darby Canine Kidney (MDCK) Cells - a model for the BBB. To do so, the cells are interfaced with a nanolayer metal electrode and an impedance signal is applied over the frequency range of 1 Hz to 100 KHz. The cell monolayer is modeled as a parallel RC circuit, and the resistance and capacitance are recordered before and after the addition of PAO to the media. A comparison of our measurement system to more traditional systems will be discussed. Our results clearly show the effect of occludin disruption on the overall impedance of the monolayer, and our system is well suited for understanding kinetic interactions at the BBB.

The highly-regulated transport of electrons within cells underpins a number of central biological processes including metabolism, respiration, and signal transduction. Interfacing living cells with electrodes offers the opportunity to control and monitor these key biological processes electronically. While several types of nanostructures can move electrons into cells, these structures cannot precisely route electrons to specific pathways, thus blunting the ability to control cellular behavior. We have recently demonstrated that by transplanting synthetic genes into Escherichia coli, we can introduce protein-based electron nanoconduits into this industrial organism. These electron nanoconduits transport electrons between intracellular electron carriers and extracellular metal ions, solid metal oxides, and electrodes. By adjusting the electrode bias, E. coli with electron nanoconduits can accept, as well as donate, electrons from an electrode. We also demonstrate that this active interface allows external electronic over a key biological process, metabolism. When our engineered E. coli deliver current to an anode, their metabolism undergoes a significant shift towards more oxidized products. Alternatively, by supplying electrons to electron nanoconduit-containing E. coli, we can drive higher production of reduced metabolites. Lastly, we show how by linking signaling systems to production of electron nanoconduits, we can use engineered E. coli-microchip hybrids to serve as autonomous, millimeter-scale biosensors. Thus, this work provides a blueprint for using protein-based materials to enable exchange energy and information between living cells and electronic systems, and has direct applications in bioelectronics, biosynthesis, biosensing, and biocomputing.

In recent years, research on organic electrochemical transistors (OECTs) is rapidly increasing due to its potential applications in bioelectronics.^{1, 2} Although flexible substrates are critically required to produce devices that conform to any deformable surface of the targets, fundamental physics of flexible OECTs are remain largely unexplored. In this research project, we developed low cost, transparent, and micro-scale OECTs arrays based on conducting polymer, poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS), on a #64258;exible poly(ethylene terephthalate) (PET) substrate. Significantly, the PEDOT:PSS film (spin-coated from Clevios^TM PH1000 PEDOT:PSS dispersion mixed with 5% glycerol), without the addition of any cross-linking agent, shows robust adhesion on the substrate even after 3-month water immersion tests. Transistor channel lengths as short as 5 um are achieved by patterning with a biocompatible fluorinated photoresist. Bending tests show that the film conductivity keeps stable at different bending angles. This work significantly contributes to the organic bioelectronics research aiming at practical applications.
1. S. Zhang, P. Kumar, A. S. Nouas, L. Fontaine, H. Tang and F. Cicoira, APL Mater 3 (1), 014911 (2015).
2. H. Tang, P. Kumar, S. Zhang, Z. Yi, G. D. Crescenzo, C. Santato, F. Soavi and F. Cicoira, ACS Appl Mater & Inter 7 (1), 969-973 (2015).

We demonstrate a strategy to fabricate patterns of highly-conducting reduced graphene oxide in flexible, strong and tough bionanocomposites comprised of silk fibroin (SF) and graphene oxide (GO) via an electrochemical reduction process. A pre-patterned photoresist film is transferred onto the GO-SF nanocomposite and acts as a stencil for the deposition of aluminum reductant. Acid-promoted oxidation of the aluminum induces the localized reduction of the GO component left uncovered by the stencil. The photolithographic origin of the stencil and high fidelity of the stencil to a master pattern enables a wide range of reduced GO shapes and features to be integrated into GO-SF. Tuning the degree of reduction affords additional control over depth of the conductive patterns. The resulting patterned composites are flexible yet highly robust due to the presence of silk fibroin acting as a multifunctional binder to GO flakes. The ability to pattern high resolution, high conductivity pathways in flexible, yet strong, GO-SF films makes this bionanocomposite system a promising microelectronic platform for applications in smart clothing (E-textiles), compliant interconnects, and flexible displays.

Photothermal conversion is a common process that happens in nature, including transpiration at the leaf surfaces and the heating of butterfly wings in cold climate. It is also an important process that is applied extensively in industrial applications, including solar-driven desalination, solar-driven distillation, and solar thermal storage systems. One of the key photothermal conversion processes in industrial applications is the light-driven evaporation process, in which the illuminating light is converted into thermal energy to drive the liquid-to-vapor phase-change process. Conventionally such light-driven phase-change process relies on the heating of the bulk liquid to the phase-change temperature using the thermal energy generated through the photothermal process. Inspired by the natural phase-change processes, in which the thermal energy is delivered locally to the phase-change interface, we developed a photothermal conversion system that also focuses the incident solar light at the evaporation interface. Such system involves the use of light absorbing thin film to trap the solar light at the interface and also convert the light to thermal energy locally to heat up only the liquid at the phase-change interface. The focused heating avoids the heating of the bulk liquid and minimizes the heat loss during the phase-change process. The free floating nature of the system enables the tracking of the conversion interface with the phase-change interface. The flexible and reusable nature of the system also offers promises in large scale applications. At the second part of the presentation, we will also discuss the photothermal storage system that is inspired by the natural systems. In current commercial photothermal storage system, heat storage is achieved through thermal conduction and diffusion within the storage media. Inspired by the heating process of black butterfly wings in cold environment, we developed a photothermal charging approach that is based on the bulk optical charging rather than the thermal conduction based charging mechanism. The performance of both systems and the potential application of the optical charging system will also be discussed in the presentation.

Humankind is in great need of new energy sources. The use of solar radiation for powering the planet would fulfil the energy requirements of Earth&’s inhabitants as well as greatly mitigate tension flares arising from the uneven distribution of fossil fuels and environmental problems associated to their extraction procedures. How to proceed? Mother Nature is inspiring: all life on earth is based on the conversion of the solar radiation into high energy molecules, including gas and oil human beings are consuming these days, by mean of the so-called primary photoconverters, i.e. the photosynthetic organisms, plants, algae and some kind of bacteria. By learning the lesson from Nature, researcher should set the goal of assembling artificial systems capable of exploiting solar energy for photocatalysis and electrical energy production [1], i.e. mimic photosynthesis. Not an easy task of course, but a large number of laboratory are heavily involved since the last 25 years in the field of artificial photosynthesis and encouraging results are being obtained.
The photosynthetic apparatus used by photosynthetic organisms to convert solar energy and drive their metabolism is the photochemical core where photoconversion takes place, and is constituted by a protein portion allocating several pigments directly involved in the harvesting of solar light and in the subsequent sequence of electron transfer reactions which eventually lead to the formation of an electron-hole couple to be used for any energy requiring process. In artificial photosynthesis the role of the protein scaffold in often ignored and attention is devoted to assembly molecular system for optimising light harvest and electron-transfer reactions, focussing to the “less-complex” portion of the photosynthetic apparatus [2].
What would be a different paradigm in artificial photosynthesis? Assemble artificial photoconverters using genuine natural components formed by hybrid organic-biologic systems [3]. The hybrids have a central protein, the so-called photosynthetic reaction center (RC) that converts sunlight into a charge-separated state having a lifetime sufficient to allow ancillary chemistry to take place. The RCs can be eventually garnished with opportune organic moieties to be used for different applications [4].
The state of the art of these hybrid organic-biologic photosynthetic assemblies will be reviewed.
References
[1] P. Maroti, M.Trotta in CRC Handbook of Organic Photochemistry and Photobiology, 3^rd ed, Boca Raton, FL, 2012; V. Balzani, N. Armaroli. Energy for a Sustainable World: From the Oil Age to a Sun-Powered Future. 2010. ISBN: 978-3-527-32540-5.
[2] Kremer, A; Bietlot, E. Chemistry-A European Journal, 21 (2014), 1108 - 1117.
[3] F. Milano, R.R. Tangorra et al., Angew. Chem. Int. Ed., 51 (2012), 11019 - 11023.
[4] Operamolla A., R. Ragni et al., J. Mat. Chem. C, 2015, DOI: 10.1039/C5TC00775E.

Most currently used solid-state luminescent materials are based on inorganic semiconductors, phosphors and quantum dots or consist of synthetic hydrocarbon compounds. Here, we describe a distinctly different, novel class of solid-state emitters offering unique optical properties - the biologically produced fluorescent proteins. In contrast to many organic dyes, the special molecular structure of these proteins ensures that in solid-state the protein fluorophores have a fixed interspacing of 3-4 nm. This suppresses concentration quenching and enables strong optical amplification (g = 22 cm^-1) in thin protein films. We use protein films to fabricate efficient solid-state vertical cavity surface emitting micro-lasers with thresholds below 100 pJ and single-frequency operation.
We also demonstrate efficient lasing from multiple photonic states in multi-lambda microcavities filled with self-assembled rings of recombinant eGFP in its solid state form. The lasing regime is again reached at low excitation energies, but for these longer cavities lasing occurs from cavity modes dispersed in both energy and momentum. The distribution of lasing states in energy is induced by the large spectral width of the gain spectrum of recombinant eGFP (FWHM = 25 nm). Our results imply that there is considerable self-absorption in eGFP and that strong exciton-photon coupling may be observed in fluorescent proteins if suitably designed resonators are used.
In addition, we find that natural self-assembly enables fabrication of protein ring resonator lasers and that solid-state blends of proteins emitting light of different color support strong Förster resonance energy transfer (FRET). The sensitivity of self-quenching and FRET to the intermolecular distance allows all-optical sensing.
Our results demonstrate that the naturally optimized, unique structure of fluorescent proteins can be harnessed in various settings, and provide bio-inspiration for further improvement of synthetic luminescent molecules or nanoparticles.
[1] M. C. Gather, S. H. Yun, “Bio-optimized energy transfer in densely packed fluorescent protein enables near-maximal luminescence and solid-state lasers”, Nature Communications 5, 5722 (2014)
[2] C. P. Dietrich, S. Höfling, M. C. Gather, “Multi-state lasing in self-assembled ring-shaped eGFP microcavities”, Applied Physics Letters105, 233702 (2014)

In the field of bio-inspired anti-refection structures, most of the attention has been dedicated so far to subwavelength protuberances (nano-pillars, nano-hemispheres, etc.) that can be found by insects, for example on the moth cornea. Conversely, the potential of some flower petals for anti-reflection purposes still lie largely uncovered.
For this reason, we investigated the optical properties of Rosa and Viola petals, whose surface corrugations are characterized by a dual-scale structure made of micro-cones decorated by nano-features. The micro-cones involved benefit from an aspect ratio of up to 2, are closely packed and present some disorder in orientation and dimensions which are all beneficial properties to achieve low reflection losses. In this communication, we discuss the role of those dual scale structure and show that those characteristics lead to broadband and omnidirectional anti-reflection properties, where the window reflectance can be maintained below 5 % for an angle of incidence (AOI) of 80° and for a spectral range of 400 to 1200 nm. It is noteworthy that strong forward scattering is also achieved, which is not the case for regular subwavelength structures acting on the refractive index gradient only. Thus, light collection and light trapping can be simultaneously addressed, making the implementation of those dual-scale structures particularly convenient for photovoltaic applications.
In order to demonstrate the latter point, we replicated the petals surface over around one cmsup2; by a soft imprint lithography technique, and incorporated the generated replicas into organic and inorganic thin film solar cells. Subsequent integrated reflection measurements showed a significant reduction of the reflected light under all AOI compared to a flat surface, evidencing only 1 % reflection for AOI close to the normal and 8% for an AOI of 80°. The average reflection losses could therefore be reduced by almost 75 %. Furthermore, the transmitted light experiences strong scattering thus elongating its optical path within the absorbing layer, which finally leads to a 10% relative increase in the efficiency of the organic solar cells.
Lastly, the replicated structures posses a super-hydrophobic wetting behaviour, potentially preventing solar cells from accumulating pollution.

Photosystem I (PSI) and Photosystem II (PSII) are the main protein complexes involved in the photosynthesis process. They have the ability to capture sunlight and generate electron-hole pairs, making them attractive sensitizers in energy conversion devices such as photo-electrochemical (PEC) cells. PSI and PSII, along with cytochrome b6f and other protein complexes are bound in the lipid bilayer of the thylakoid membrane of photosynthetic organisms. Previously, isolated PSI, PSII and thylakoid membranes have been integrated on the electrode mainly through linker molecules. However, the resistance generated by using linker molecules encourages electron-hole recombination, and thus necessitates the addition of an electron mediator, which consequently degrades the performance of the cell. Also, a PSI-sensitized PEC cell requires a sacrificial electron donor to regenerate PSI.
The present study demonstrates the fabrication of linker-free and electron-donor and mediator-free PEC cells by aerosol techniques. The thylakoid membrane, extracted from Synechocystis 6803, a cyanobacterium, is processed through three different surfactant concentration addition methods, (1) no surfactant, (2) surfactant addition after centrifuge and (3) surfactant addition before centrifuge. Using electrospray, the membrane is then deposited on the 1-D-single crystal TiO₂ nanostructure, synthesized by aerosol chemical vapor deposition,¹ enabling the linker-free attachment of the photosynthetic pigment-protein complexes on TiO_2.^2,3 A 3-electrode PEC cell was fabricated using sensitized TiO₂ as the working electrode, platinum as the counter electrode and Ag/AgCl as the reference electrode and tested in the absence of any electron donor or mediator in the 0.1 M KCl electrolyte. The maximum photocurrent density, 6.7 mA cm^-2 under UV + visible light and 12 mu;A cm^-2 under only visible light illumination, was observed for case 3. It is found that the bulky lipid molecules hinder the electron transfer from the membrane to TiO_2, thus giving the lowest performance for case 1. The surfactant functions as a solubilizing agent and breaks the membrane. Higher concentrations of the surfactant affects the assembly of PSI, PSII and cytochrome b6f, their re-suspension into the electrolyte, and the electron transfer; thus affecting the overall performance of the cell. The proposed mechanism of electron transfer in the membrane is similar to the Z-scheme of photosynthesis. The electron transfers from PSII to PSI via cytochrome b6f and then reaches the conduction band of TiO₂. From there, it travels in the circuit and produces hydrogen at the counter electrode. The electron at PSII is regenerated by the oxidation of water to oxygen, thus mimicking natural photosynthesis.
(1) An, W.-J. et al., The Journal of Physical Chemistry Letters 2009, 1, 249-253
(2) Shah, V. B. et al., Langmuir 2015, 31, 1675-1682
(3) Zhu, L. et al., international journal of hydrogen energy 2012, 37, 6422-6430

Micro-lenses have commonly been deployed for enhancing out-coupling of light in organic light emitting diodes (OLEDs). These lenses widen the escape cone for total internally reflected light incident at air-substrate boundary and help in extracting substrate mode of light. The maximum outcoupling depends on various parameters such as lens diameter, height as well as packing density of these micro-lenses.
Here we have demonstrated a novel method for fabricating microlenses utilizing masters comprised of patterned microbes. Saccharomyces cerevisiae (Baker&’s yeast), generally used in a biological laboratory, is allowed or restricted to grow in selected areas on a chemically treated polyvinylidene fluoride (PVDF) membrane which acts as a substrate. This substrate with patterned microbes over it serves as a master template for casting polydimethyl siloxane (PDMS) microlenses. The process is comprised of two approaches - microbial approach, where microbes are allowed to grow on selected regions; and antimicrobial approach, where microbial growth is restricted on specified regions.
Inspiration for this work is derived from a tree, where scratched features on its bark get transformed into protrusions as a result of self-healing process, rather than indentations which are generally seen on other trees. An attempt to mimic this phenomenon on a reasonable length and time scale has led to the development of the present process.
Inkjet printing, a maskless and direct writing technique, has been employed for dispensing a suitable ink for both microbial and antimicrobial approaches. The ink is a culture of microbes in the case of microbial approach and an antimicrobial agent in antimicrobial approach. The patterns of microbes thus fabricated serve as masters for preparing PDMS mold. For investigating luminous/outcoupling enhancement, red, green and blue OLEDs are fabricated on which microlenses are directly attached to the air side of the OLED glass. Although the micro-lens arrays achieved in the antimicrobial approach are random in nature, the luminous enhancement of 1.12X has been obtained. On the other hand, microbial approach presents closely packed microlenses of diameter 500 microns and height 300 microns. A maximum enhancement of 1.24X has been achieved using these microlenses.

Conjugated polymers have recently been considered as promising materials for the optical control of living cells electrical activity [1,2]. Specifically, organic thin films based on poly(3-hexylthiophene) (P3HT) were successfully interfaced with neurons for in vitro cell photostimulation, and with retinal tissues in ex vivo studies for restoring impaired light sensitivity [3,4]. However, the possibility to use other organic semiconductors sensitive to different wavelengths was never considered, and a comparative study among different conjugated polymers is still lacking. The potential opportunity of realizing a polymer-based artificial retinal prosthesis that could in principle be color sensitive, demands an immediate investigation of different polymers in contact with living cells. Moreover, the development of an efficient and reliable opto-interface requires a detailed study of their properties at different steps of the bio-interface fabrication.
In this work, we have extensively characterized four different organic semiconducting polymers with different optical band gaps (Poly[2,1,3-benzothiadiazole-4,7-diyl[4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b']dithiophene-2,6-diyl]], PCPDTBT, Regio -regular Poly(3-hexylthiophene), rr-P3HT, Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene-vinylene], MEH-PPV and Poly[9,9-dioctylfluorenyl-2,7-diyl], PFO), in terms of wettability, surface morphology, interaction with the protein adhesion layer, electrochemical stability, capability to sustain cell seeding and cell photo-stimulation. Our results demonstrate that all selected polymers withstand the thermal sterilization protocol and protein adhesion but provide different cell viability. In terms of opto-excitation, we show that visible light depolarizes the resting membrane potential of cells seeded on top of PCPDTBT, P3HT and MEHPPV but induces detrimental cellular effects in the case of the high gap PFO. These findings provide a useful tool for cell optical stimulation all over the visible range and suggest the possibility of combining three different materials for the fabrication of a trichromatic based artificial photoreceptor.
References
[1] V. Benfenati, N. Martino, M. R. Antognazza et al. Adv.Health. Mater. 3, 392-399 (2014).
[2] N. Martino, P. Feyen, M. Porro et al. Sci. Rep. DOI: 10.1038/srep08911.
[3] D. Ghezzi, M.R. Antognazza, R. Maccarone et al. Nat. Photon. 7, 400-406 (2013).
[4] V. Gautam , D. Rand , Y. Hanein and K. S. Narayan. Adv. Mater. 26, 1751-56 (2014).

DNA, a unique one-dimensional biopolymer with the sequence of four bases, plays an important role for all livings, and is well known to have information in itself with an address of 0.34 nm base-pair pitch. DNA has been collecting a lot of interest as a functional material since DNA forms complex with functional molecules such as organic dyes, metal complexes and conductive polymers through electrostatic binding, intercalating and groove binding. These interaction modes in DNA with highly ordered structure give unique complex structure, resulting in the attractive electronic and photonic functions.
In this paper, we would like to focus on the application of DNA complex to novel electrochemi- luminescent (ECL) material. ECL is a light emitting phenomenon induced by electrochemical reaction. We have reported that the stability, emission response and intensity of the ECL device are improved by using application of AC voltage. In this research, we fabricated novel DNA/Ru(bpy)₃²⁺ film-modified electrode, and also studied AC-operated ECL characteristics of the electrochemical cell using the novel modified electrodes. As a result, the ECL was obtained from quite high frequency of 10 kHz, enabling quick response time of < 100 mu;(micro)sec.

Brightest colours in nature are produced when light repeatedly scatters against periodically organized interfaces within nanostructured materials. This brilliant iridescent colouration is frequently used in many insect and animals but also in different species of plants. Within the latter, one of the most striking examples of structural colour is the Pollia condensata [1]. The blue pixelated appearance of its fruits is the results of chiral multilayered structures composed of cellulose micro-fibrils, which from a layered structures. In each component layer, cellulose micro-fibrils lie parallel to one another, with successive layers offset from each other at a small angle, so that the direction of the parallel-aligned micro-fibrils changes consistently, rotating from one layer to another and producing an intense colour-selective reflection. Similar architectures can be obtained with the same material as nature: cellulose. Biomimetic with cellulose enables us to fabricate novel photonic structures using low cost materials in ambient conditions [2-4]. Importantly, it also allows us to understand the biological processes at work during the growth of these structures in plants.
In this work the route for the fabrication of cellulose-base architecture will be presented and the optical properties of cellulose artificial structures will be analyzed and compared with natural one.
[1] S.Vignolini et. alPointillist structural color in Pollia fruit PNAS 109, 15712 (2012).
[2] S. N. Fernandes et. alStructural Color and Iridescence in Transparent Sheared Cellulosic FilmsMacromol. Chem. Physic. 214, 25-32 (2013)
[3] A. G. Dumanli et. al Digital Color in Cellulose Nanocrystal Films, ACS Appl. Mater. Interfaces ACS Appl. Mater. Interfaces 6 (15), pp 12302 (2014)
[4] A. G. Dumanli et. al Controlled bio-inspired self-assembly of cellulose-based chiral reflectors, Adv. Opt. Mat. 2, 646 (2014)

Silk protein, extracted from the Bombyx mori caterpillar, has been re-invented as a biological base materials in bio-optics and electronics. Optical transparency of a silk film makes it possible to engineer a range of nano-optical components such as a single-mode biological laser and a photonic crystal by nanofabrication techniques. Beyond the optical building material, our group has been trying to utilize silk fibroin as a functional optical material. One study is the use of silk fibroin hydrogel, which can accommodate water molecules by up to 60% in volume. The hydrogel properties can facilitate a high tunability of optical resonators through the control of the swelling ratio.
Here we report lithography-free, large-area, and water-responsive super absorbers and color filters at visible and near-infrared frequencies based on metal-insulator-metal (MIM) thin film resonators. A resonance tune of over 100 nm between a water environment and an alcohol environment are achieved despite the very small refractive index difference of these liquids. Such an effect is not expected in conventional refractometer-based optical sensors. As a possible application, we examine spectral responses when a free standing silk MIM resonator is placed under slices of biological tissue of variable thickness. We also confirm that the silk MIM resonator operating at the wavelength of 800 nm, in the near-infrared window of biological tissues, shows lower scattering loss than those at visible. This structure can be envisioned as protein-based contrast agents that do not require other chemicals.
Our silk MIM resonators are promising for various applications, including biochemical sensing and photothermal patch. In addition, continuous and unstructured geometry is enabled by cost-effective large-area and lithography-free fabrication only coating a silk film and metal layers.

Hybrid systems in which organic emitters are covalently bound or embedded into mesoporous nanostructured silica have recently attracted attention as versatile multifunctional materials for applications in photonics, sensing and bioimaging.[1] Diatoms are unicellular photosynthetic algae bearing a three-dimensional mesoporous silica skeleton (frustule) whose size and morphology is strictly dependent on the algal species. These microorganisms can be regarded as low cost bio-factories for a large number of 3-D biosilica nanostructures with reproducible shape and micro-to nanoscale features. Frustules have a highly ordered “layer by layer” hierarchical architecture in which every layer has a periodic disposition of pores: for this reason they can act as natural photonic crystals and applications as optical microlens, filters, beam splitters and laser cavities can be envisaged.
In this context, integration of organic emitters into diatom frustules is a promising approach to afford bio-hybrid luminescent materials for laser technology or light emission modulation.
Here we present the synthesis of a series of organic and organometallic dyes and their incorporation into frustules of the Thalassiosira weissflogii and the Coscinodiscus wailesii centric diatoms. In particular, we demonstrate both in vitro and in vivo fluorochromation of the diatoms biosilica affording new hybrid systems which retain the emissive properties of the incorporated dyes as well as the natural frustules morphology. This approach discloses intriguing possibilities in the massive biotechnological production of photoactive nanostructured materials, whose features can be finely tailored by chemical design of the light emitting molecules and by selecting and modifying the characteristics of the microorganism used.
[1] J. E. N. Dolatabadi, M. de la Guardia Trends in Analytical Chemistry,2011, 30, 1538-1548.
[2] S. R. Cicco, D. Vona, E. De Giglio, S. Cometa, M. Mattioli-Belmonte, F. Palumbo, R. Ragni and G. M. Farinola Chem Plus Chem2015 DOI: 10.1002/cplu.201402398

Various animals in nature are known to exploit nanometric conformation of their organic materials to influence the light in structures considered as photonic crystals. Examples are butterflies and beatles. Also in Diatoms [1], that are single cell organisms, their biomineralised cell walls (frustules) seem to show photonic crystal behavior. Frustules are composed of two “caps” (valves) overlapped like a Petri dish and held together by a siliceous ring (girdle): both valves and the girdle present a periodic or quasi-periodic structure. Different species show different type of periodicity: here we studied the Thalassiosira Weissflogii, a diatom species with central symmetry, not yet studied in literature. We studied the optical behaviour of the cell walls (valves and girdle) of naturally grown diatoms and diatoms fed with a new synthesized blue light emitting aryleneethynylene fluorophore (BPE).
To fully characterize the optical response of the diatoms we performed two types of measurements: optical transmission by means of a confocal microscope continuously tunable in wavelength from 475 nm to 1050 nm, and photoluminescence by means of a continuous wave (cw) 375 nm diode laser. Transmission measurements showed a complicated photonic behaviour of the whole diatom: the different conformation of the valves and the frustule give rise to different photonic band gaps [2], with a higher photonic crystal behaviour of the girdle. This is shown by collecting multiple spectra punctually on the different components of the cell wall. A possible further confirmation of this phenomenon is the photoluminescence of the dye. Indeed the emission spectrum of BPE incorporated in the biosilica structure is modulated by the silica walls of the diatom. Moreover, by tilting the angle of the fiber and acquiring the photoluminescence signal, the rise and the wavelength position of the peaks change with the angle. This transmission modification with the angle of detection of the periodic structure is consistent with the photonic crystal behaviour. These measurements confirm that the Thalassiosira Weissflogii diatom can be considered as “living photonic crystal” and it could be exploited for in vivo production (by feeding with appropriate molecules) of optical and photonic structures.
[1] T. Fuhrmann et al. Applied Physics B, 78, 257, 2004.
[2] K. Kieu et al., Optics Express, 22, 15992, 2014

Diatoms are found in nearly every aqueous environment and play a vital part of the global primary production system contributing with up to 25 % and are efficient light harvesting organisms. Unique to diatoms are the hard cell wall, called the frustule surrounding the single cell. The frustule is made from bio-synthesized silicate, perforated by wavelength sized features where the morphology of the nano-structured “greenhouse” is species dependent. Diatoms would therefore make for one of the most interesting “green” resources since it has not only potential as a biomass production system but also for nano-structured inorganic material.
To shed light on the biological significance and to integrate diatomic frustules as active material in devices a fundamental understanding of how light interacts with the frustule is needed. In this study we focus on centric diatoms, i.e. having rotational symmetry where morphological parameters vary between the different investigated species. We report how light interacts with the frustule in the wavelength range from UV-A (320-380 nm) to NIR (900 nm). High resolution spectroscopy and local spectroscopy is used to identify variations in the transmitted light caused by the nano-structured frustule. Both non-polarized and polarized light is used in the study to simulate the influence of the polarization of light when it inters water, the habitat of the living diatom. Furthermore we show, by placing the frustule on a quartz half sphere how light transmission is a function of the angle of incidence and wavelength.
This work was part of the project ALPHA, project number 12-127569 of the Danish Council for Independent Research | Technology and Production Sciences.

Photonic crystals are structures formed by long range periodic arrangements of dielectric materials in sub-micrometer scale resulting in band gap structures. Natural photonic crystals, e.g., mineral opal, are composed of sub-micrometer-sized, spherical amorphous silica nanoparticles, arranged in close-packed 3D lattices. Color-producing biological photonic crystals are also common in which biopolymers can organize into ordered structures in feathers, topographic structures, and skins creating devices providing an ecological niche for the organism. Synthetically produced photonic crystal have unique optical properties that offer a variety of applications, e.g., sensor devices, zero threshold lasers, LEDs, optical waveguides and switches, finding commercial use in telecommunications. The periodically ordered organization of structural features in photonic crystals can be ridges, nanoparticles, nanowires that can cause light scattering or inference in the visible and near visible spectra. For practical implementations, however, the uniformity of size and degree of long-rage order and other factors, e.g., types of defects and their concentrations, can be critical. In biological systems these key factors are regulated by proteins and polysaccharides coded by the genes while in geological systems, these are controlled by the thermodynamic equilibrium achieved over long periods of times, and high temperature and pressure. In technological systems these key factors are difficult to achieve under practical conditions, the major challenge for large scale implementation preventing affordable and scalable fabrication techniques. Although 2D photonic crystals can be fabricated by top down techniques, such as e-beam lithography or focused ion beam milling, 3D structures have been formed using bottom up, colloidal techniques via self-assembly. In the latter case, monodispersed nanoparticles with defect-free packing (preventing agglomeration) are needed but are challenging to achieve. There is a need, therefore, for simple methods for synthesizing monodispersed particles and modulating surface properties for fully exploiting the advantages offered by self-assembly. Herein, we describe a single step method for controlling synthesis, stabilization and self-assembly of silica particles into ordered 3D structures using short peptides. Here we utilized a second generation quartz-binding dodeca-peptide, QBP3), designed in silico by all-against-all comparison of first generation phage-display-selected peptides. Containing basic residues, QBP3 assists base-catalyzed hydrolysis of orthosilicates and, also, acts as a capping agent, narrowing the size distribution of the particles while increasing efficiency of self-assembly by balancing the net charge of the particles. We monitored the reaction kinetics by optical density, characterized particle size by SEM, and evaluated self-assembly and photonics properties via UV-vis absorption spectroscopy. Supported by NSF-MRSEC.

It has been known for several decades that black butterfly wing scales are evolved as an efficient absorber of visible light to regulate their body temperature. In addition to absorbing melanin-chitin composite, the porous photonic nanostructures present on the black wings attribute to the light collection and emission mechanisms. However, only little attention has been given to the physics involved in the two-dimensional random nano-hole structure and triangular grating like shaped ridges, which are intrinsically part of the black butterfly micro/nanostructures. Although black butterfly photonic structures are modelled by a periodic distribution of scattering elements for most models investigated so far, there is an enormous potential for photonic materials that goes beyond regular photonic structures, especially for angular aspects. Here, we report using 3D finite element-method (FEM) model, optical manipulation of light by Pachliopta aristolochia's wing complex nanostructures. Mimicking the original Pachliopta aristolochia wing's nanostructures in melanin-chitin composite, we first demonstrate and reproduce the high absorption of the wing scales in the visible regime. By further controlling the filling fraction and dispersion in size and position of nanoholes within the absorbing layer step by step, we achieve an efficient light trapping scheme. We show that manipulating the correlation between nano holes using Lubachevsky-Stillinger algorithm inspired by the butterfly pattern, a high-performance omnidirectional and polarisation-tolerant absorber can be numerically achieved. Furthermore, these optimized random 2D nanostructures appear particularly relevant for increasing the absorption in thin film solar cells as well. In addition, the use of such structure enables to relax the technological constraints with respect to their periodical counterparts and to use fabrication technique, such as polymer blend lithography, which is applicable onto large surfaces.

In animals colors are produced by either pigment coloration or structural colors. Structural colors are caused by the interaction of light with structures that have periodicities comparable to the visible light wavelengths. This leads to selective reflection of particular wavelengths through interference. Many taxa have independently evolved ways to produce structural colors using intra-cellular arrays of guanine crystals interspersed with cytoplasm. One of the most striking examples of such photonic arrays are the males sapphirinid copepods, small marine crustaceans that produce a variety of different colors. In order to understand how the different colors are produced, we designed a fully correlative experiment in which the reflectance of individual copepods was first measured using a tailor made microscope, and then the thicknesses of the crystal and cytoplasm layers were measured using cryo-SEM on the same individuals. Using this approach we were able to demonstrate that variations in cytoplasm layer thickness are mainly responsible for the different reflected colors (1). Furthermore, we show a strong angular dependence of the copepod color on the orientation relative to the incident light, which can account for its appearance and disappearance during spiral swimming in the natural habitat (1).
In many of the systems the spacing of guanine crystals and cytoplasm are immobile, but there are a few known cases where they are not. The Neon Tetra fish changes its structural color of its lateral stripe from blue-green to indigo in response to different light stimuli. Lythgoe & Shand suggested that the variation in spacing is due to a change in osmotic pressure, which results in the inflow of water into the guanophore (specialized cells containing guanine crystals) (2). This inflow of water leads to swelling of the guanophore cell and consequently to an increase in crystal spacing. In contrast, Nagaishi et al suggested that the tilt angle of the crystal platelet varies, leading to a change in platelet spacing (3). Using synchrotron radiation combined with data from cryo-SEM, we were able to determine that the change in the color of the lateral stripe of the Neon is due to an angular shift of the guanine crystals. This angular shift results in a change in the d spacings between the crystals (4).
Reference:
1. D. Gur et al., Structural Basis for the Brilliant Colors of the Sapphirinid Copepods. J. Am. Chem. Soc., (Jun 26, 2015).
2. J. N. Lythgoe, J. Shand, Changes in spectral reflexions from the iridophores of the neon tetra. J. Physiol.325, 23 (Apr, 1982).
3. H. Nagaishi, N. Oshima, Ultrastructure of the Motile Iridophores of the Neon Tetra. Zool. Sci.9, 65 (Feb, 1992).
4. D. Gur et al., The Mechanism of Color Change in the Neon Tetra Fish: a Light-Induced Tunable Photonic Crystal Array. Angew. Chem. Int. Ed. Engl., (Apr 27, 2015).

Animals and flowers have evolved a wide variety of micro- and nanostructured material morphologies that provide the individual host organism with distinctive and frequently variable coloration. Colors based on light interference and diffraction phenomena, termed “structural colors”, have been identified as the source of the unique appearances of many terrestrial organisms, and are prominently featured on the wings, thorax and abdomen of insects, the torsi of spiders or the feathers and the skin of birds. Photonic structures have also been found to play a significant role in ensuring the stunning visual appearances of many marine animals. The constraints imposed on the propagation of light under water, the tight competition for resources and the constant exposure to a diversity of predatory organisms have resulted in a huge variety of visual display, signaling and light harvesting strategies that rely on the integration of photonic structures in unique material systems, which rivals and potentially even exceeds the diversity of photonic materials found in terrestrial and avian species. Here, we present the mineralized composite photonic architecture, which is buried in the shell of the fingernail-sized blue-rayed limpet Patella pellucida. The structure that is responsible for the bright blue stripe patterns, which can be perceived underwater as “blue flashes” from several meters away, consists of a localized layered stack of calcite lamellae with uniform thickness and inter-lamella spacing superposed on a disordered array of absorbing colloidal particles. Regular undulations of the multilayer and a variation in layer orientation in each stripe ensure that the reflected blue light can be perceived in a wide angular range, enhancing the organism&’s visibility. The absorbing colloidal particles beneath the multilayer provide an absorbing background to enhance the spectral purity of the reflected blue light. We present a full structural, elemental and optical characterization of this marine photonic system, and provide a hypothesis regarding its benefit for the limpet. Currently, we are also investigating the in-vivo formation of mineralized photonic structures in the limpet&’s shell, aiming to gain insight into the phenomena underlying the morphogenesis of calcified photonic materials and to identify the mechanisms that provide the required micro- and nano-scale structural control.

Nature uses colloidal structures for a myriad of properties from color to repellancy. Synthetically, colloidal crystals can be used to template inverse opals, creating ordered, porous structures. When this structure occurs on the 100-nm length scale, the porous structure provides control over both light (photonic effects) and fluid flow (wetting effects). Inverse opals are widely used in many applications that take advantage of these properties, including optical, wetting, sensing, catalytic, and electrode applications [1]; however, high quality structures are necessary to maintain the advantageous properties. Using a bio-inspired approach, highly ordered, crack-free, silica inverse opals can be grown by co-assembling the colloidal template with a sol-gel precursor using evaporation-induced self-assembly [2]. Here, we describe how different aspects of the sol-gel chemistry can be further used to control both the shape [3, 4] and composition [5] of these photonic structures. In particular, temperature-induced condensation of the silica sol-gel precursor can be used to control the shape of the inverse opal pores [3], and silica and titania precursors can be mixed to control the refractive index of the structure [5]. By controlling the structure and composition with sol-gel chemistry, we can tailor both the optical [3,5] and wetting [4] properties, which have important effects for the various applications. In this way, sol-gel chemistry can be used to make inverse opals with functions beyond those found in nature.
[1] K. R. Phillips et al, submitted.
[2] B. Hatton et al. PNAS, 2010.
[3] K. R. Phillips et al, Chem Mater, 2014.
[4] K. R. Phillips et al, Langmuir, 2014.
[5] K. R. Phillips et al, in preparation.

Acetylcholine is an important neurotransmitter and neuromodulator of the nervous system. Both central and peripheral nervous systems respond to injury and control inflammation by direct neural projections and their resulting neuroendocrine reflexes. This signaling, or brain-immune communication, is not well understood. A sensor for acetylcholine would be beneficial for tracking the distinct molecular and neurophysiological mechanisms that govern these complex pathways. However it is difficult to quantify both spatial and temporal fluctuations of acetylcholine signaling. One limitation in imaging these responses is the tight architecture of neurons and synapses. Previously, we developed a DNA-dendrimer nanosensor for sensing acetylcholine and advanced our technology for real-time imaging of acetylcholine fluctuations. These DNA nanosensors are created in stellar dendritic-shaped DNA structures with conjugated sensing components. They are designed to take advantage of DNA&’s efficient self-assembling to maximally load sensing components that employ acetylcholinesterase as a recognition element alongside pH sensitive fluorescent reporters. This design is paired with tethered alpha-bungrotoxin to selectively immobilize the nanosensors to nicotinic acetylcholine receptors of the postsynaptic neuron. The nanosensor accommodates the enzyme and fluorophores in an optimal configuration for sensing; resulting in improved sensitivity, a brighter signal and targeting to cholinergic synapses. Imaging the volumetric release of acetylcholine in the nervous system is done in highly transparent juvenile Ambystoma mexicanum. This novel DNA nanosensor reveals acetylcholine signaling to further the understanding of distinct motor and neurophysiological mechanisms that govern the injury and immune responses of A. mexicanum.

Two-photon-excited fluorescence (TPEF) has gained widespread popularity in the biology community due to the many advantages it provides in microscopic imaging. Among various probes, semiconductor-based quantum dots (QDs) have been shown to provide a particularly powerful approach to luminescent nano-objects for bioimaging including TPEF. However, these inorganic systems suffer from several drawbacks such as toxicity, blinking... With this aim in mind, we have developed two bottom-up routes towards fully-organic alternatives.
The first one is based on the control, at the single nano-object level, of the optical responses via the design of covalent molecular structures of highly confined chromophores within hierarchical architectures. This covalent strategy led to tunable nano-objects (typically 2-6 nm in radius) which can outcome QDs in terms of brightness by orders of magnitude, show cooperative enhancement of two-photon absorption and allow fast energy transfer. These tunable, soft organic nanodots (ONDs) have proven to be of major interest as luminescent nanoparticles for in vivo bioimaging as well for sensitive detection of explosives. The second route is based on the spontaneous assembly of dedicated multipolar insoluble dyes in water. This non-covalent approach led to Fluorescent Organic Nanoparticles (FONs) showing extremely high one- and two-photon brightness (up to 10⁸ M^-1cm^-1 and 10⁶ GM). These nanoparticles (having radius of 7-30 nm) can be readily prepared using simple, expeditious and green protocols. Their color, biocompatibility and colloidal stability can be tuned thanks to a subtle molecular engineering strategy, yielding biocompatible ultrasensitive nanotracers for in vivo angiography. Hyperbright NIR-emitting FONs (thus named HiFONs) have been successfully applied to imaging in cells as well as to single particle tracking in water including dual color single particle tracking.
Finally, striking luminescence enhancement and spatial confinement at the nano-interface can be achieved in core-shell binary nanoparticles made from dedicated complementary dyes, in relation with the generation of large interfacial electric fields. This opens an intriguing route towards “molecular plasmonics”.

Bio-inspired, hybrid architectures employing quantum dots (QDs) appended with functionally active biomolecules such as enzymes have the potential to be utilized in numerous applications. Some examples include nanosensors for medical diagnostics, chemical/biological threat detection, as well as “bio-factories” in complex industrial synthetic processes. The main advantage in creating these nanofactories is that numerous studies have shown increased rates in catalysis and efficiency when enzymes are attached to nanoscaffolds. The high surface to volume ratio of QDs allows for the attachment of numerous unique moieties to the surface while still maintaining the QD&’s superior optical properties. These optical characteristics include high quantum yield, broad absorption spectra with large molar extinction coefficients, and narrow, symmetric emission spectra which all can be exploited for rapid, optical measurement. Enzymes play an important role in a myriad of industrial purposes and in medicine. However, enzymes can be quite costly and immobilizing them for retention can decrease their activity. Therefore, gaining a fundamental, mechanistic understanding of enzyme-QD nanostructures is important in the development of numerous device applications. In this work, we study how enzyme effectiveness in neutralizing a simulant nerve agent can be increased when attached to two, distinctly sized QDs. Zwitterionic ligands were appended to 525 nm or 625 nm QDs to improve aqueous stability and prevent aggregation. Distinct molar ratios of phosphotriesterase (PTE) were rapidly self-assembled to the Zn²⁺-rich QD surface via spontaneous metal coordination with PTE&’s oligiohistidine tag. PTE catalyzes the hydrolysis of paraoxon, a simulant for V-/G- agents, to p-nitrophenol which can be monitored over time by measuring the absorbance at 405 nm. We determined that the optimal ratio of PTE to QD was 6 and 8 for 525 nm and 625 nm QDs, respectively and saw a ~50-60% increase in V_max along with improvement in other kinetic parameters for PTE compared to free enzyme. Next, we explored the influence of solution viscosity and competitive inhibition on reaction kinetics. Using these results and the current model of how this enzyme functions, we determined the hydration shell surrounding the QD and attached enzymes promotes product dissociation leading to increased rates of catalysis. Along with this mechanistic elucidation, we also observed that enzyme orientation and density play crucial roles in enhanced enzyme performance. These insights are necessary for the successful optimization of enzyme-based nanostructures.

“Green” manufacturing techniques receive increasing attention as research into alternative energy harvesting technologies grows. Among these “green” techniques, the precipitation of semiconducting nanoparticles (NPs) by E. coli is a novel method. E. coli are rod-shaped bacteria that are widely used in biotechnology applications, most notably for protein synthesis. More recently, these bacteria have been genetically engineered through the expression of the Treponema denticolacysteine desulfhydrase gene to precipitate transition metal NPs from solution. This technique can be used in a broad range of nanotechnology applications, including medical imaging, disease detection, and solar cells. On the other hand, E. coli programmed with pattern formation synthetic gene circuits have the ability to generate self-organized patterns. Here, we will combine these circuits into our genetically engineered E. coli to create patterned NP devices. Our genetically engineered E. coli have great potential for the precipitation of transition metal sulfide NPs for applications ranging from photovoltaics to photocatalysis in H₂ evolution. We found that the bacterially precipitated NPs are agglomerates of 4-5 nm diameter quantum dots (QDs) in a carbon-rich matrix. Based on our initial results, we aim to develop optimal precipitation conditions and deposition protocols and characterize the morphological and electronic properties of bacterially precipitated QDs. Specifically, we focus on precipitating cadmium sulfide QDs and controlling QD properties by varying precursor concentration as well as temporal control over the particles by inducing precipitation at varying stages of bacterial growth. In short, our findings capitalize on the generation of a bacterial platform that enables environmentally friendly fabrication of functional patterned materials for optoelectronic and photocatalytic devices.

The use of biomolecules to provide bioinspired routes for the synthesis and assembly of inorganic (nano)materials under biological conditions is an area of great interest.[1] One promising route is the synthesis of gold nanoparticles (AuNPs) in water, using only peptides as the nucleation and capping agents. Recent experiments have shown that the peptide sequence used in this process can modify both the structure and properties of the resultant AuNPs.[2] To fully exploit the ability of peptides to control the size, shape and properties of the peptide decorated AuNPs, however, a deeper fundamental understanding of the interfacial interactions occurring at the molecular level is required. Experimental studies have determined the structure of the noble metal NPs generated using peptides in aqueous solution[2,3]; however, making clear connections between the structure of the adsorbed peptide overlayer and the properties of these systems, under aqueous conditions, is challenging to obtain via experimental techniques alone. Molecular simulation can provide valuable information regarding the interaction of peptides adsorbed at aqueous noble metal interfaces.[4,5] However, the majority of these studies have investigated the behavior of peptides adsorbed at periodic surfaces or with ideal faceted nanoparticles, rather than surfaces with irregular features occurring on the nanoscale. In contrast, recent experimental evidence shows that peptide-synthesized AuNPs feature surface irregularities.[3] Here, we predict the structure and binding properties of an overlayer of multiple peptides adsorbed at the aqueous interface of AuNPs with irregular surface features, for ten different peptide/AuNP systems. Our findings reveal connections between the peptide sequence used to grow the AuNP and the structure/property relationships of these NPs.
[1] Dickerson, M.B., et al.; Protein and Peptide Directed Syntheses of Inorganic Materials, Chem. Rev., 2007, 108, 4935-4978.
[2] Li, Y., et al.; Peptide-mediated synthesis of gold nanoparticles: effects of peptide sequence and nature of binding on physiochemical properties, Nanoscale, 2014, 6, 3165-3172.
[3] Bedford, N.M., Analysis of 3D structures of platinum nanoparticles by high energy X-ray diffraction and reverse Monte Carlo simulations, Solid State Comm., 2010, 150, 1505-1508.
[4] Feng, J., et al., Influence of the shape of nanostructured metal surfaces on the adsorption of single peptide molecules in solution, Small, 2012, 8, 1049-1059.
[5] Tang, Z., et al., Biomolecular recognition principles for bionanocombinatorics: an integrated approach to elucidate enthalpic and entropic factors, ACS Nano, 2013, 7, 9632-9646.

Logic circuits revolutionized the world by enabling us to create the modern computer. As for now, these logic elements are made from inorganic materials, mainly doped silicon, in the nanometer scale. However, the ability to perform complicated logic tasks is not limited to inorganic computers; Living organisms perform such tasks by using complex neuronal networks. Currently, the ability to create an in vitro computer by using neuronal cells is very limited. In this work logic circuits were created by using living matter by imposing a defined neuronal network structure. Moreover, we demonstrated a neuronal diode, neuronal AND gate and a combination of the two (AND gate which operates a diode). Once the neuronal logic circuits were built, their response to stimuli at different frequencies was tested and their transfer function was calculated. While these neuronal logic gates can be used as building blocks for neuronal computer, they could also be used for assessing the quality of the neuronal network functionality. Currently, the main parameters that are been used to assess the neuronal in vitro cultures are synchronization and correlation of neuronal firing activity. Whereas in vivo this evaluation can be represented by the animal ability to perform a task. By using neuronal logic circuits as a tool for assessing network functionality, we are able to examine the neuronal network functionality in a method that is more in vivo like, which take into account the network ability to perform a task. This work demonstrates a simple method to use living matter to create logic circuits. Moreover, these logic elements could be used in many applications such as building blocks for a computer or as a tool for assessing the neuronal network.

Beautiful shapes and patterns of the animal skins such as that of zebra are occuring from a surprisingly simple mechanism. Alan Turing developed a mathematical model, reaction-diffusion system, to predict spontaneous formation of patterns reflecting the changes of concentrations for two competing production of chemicals. Such patterns are called "Turing Patterns" and the RD system is now proven to be the principle for the evolution of graphical patterns that we see on skins of animals, fish, etc...
We have discovered electrochemical process to evolve unique Turing patterns in nano-scale for cathodic electrodeposition of hybrid thin films of zinc oxide and rhodamine B. Little addition of rhodamine B into the bath for electrodeposition of ZnO employing reduction of O₂ results in a variety of Turing pattens comprising of crystalline ZnO and solid rhodamine B. Rhodamine B is electrochemically reduced to form complex with Zn²⁺ and that is oxidized with O₂ bubbles, releasing ZnO and regenerating rhodamine B. Due to such a catalytic cycle, rhodamine B fulfills the function as an "activator" for formation of ZnO. While precipitated rhodamine B is highly insoluble and diffuses slowly, ZnO can repeat dissolution / recrystallization cycle and diffuses about a decade faster than rhodamine B, so that it prevents the growth of rhodamine B. Thus, ZnO fulfills its function as the "inhibitor" for formation of rhodamine B. This way, the conditions for Turing pattern formation by the RD model is satisfied. The structure of the hybrid materials is nicely compared to that obtained by mathematical simulation of modified RD model. Also obtained was the total 3D image of the ZnO / rhodamine B labyrinthine structure by FIB-SEM observation technique that nicely supports the film growth reflecting the "standing wave" of ZnO / rhodamine B concentrations at the frontier of the electrochemical precipitation.
In the talk will be presented the special properties of rhodamine B and will be discussed the reasons for this phenomenon. We also envision the use of such self-assembled hybrid nanostructures in hybrid solar cells to realize endless regeneration of solar panels from "one-pot".

Semiconductor nanoparticles or quantum dots are desirable for many phontonic and electronic applications due to their size tunable optical and electronic properties. Commercial use of quantum dots has been limited by costly and environmentally harmful chemical synthesis. Recently, biosynthesis has been investigated as an inexpensive, environmentally benign alternative to producing quantum dots at large scale. In this work, we show the ability of Stenotrophomonas maltophilia to synthesize not only CdS and PbS quantum dots, but PbS@CdS core-shell quantum dots with extrinsic size control. This biosynthesis is performed in water at room temperature using inexpensive precursors. Capping exchange is performed to transfer the quantum dots from an aqueous to organic phase, and optical properties for core and core/shell particles are shown in both phases. HRTEM and HAADF imaging are used to confirm the presence of a CdS shell as well as the phase of PbS and CdS nanocrystals. The functional properties of these materials are demonstrated through their incorporation into quantum dot sensitized solar cells.

We report our recent progress in the area of DNA-mediated fabrication of inorganic nanostructures. We show that DNA origami nanostructure can be used a template to control the rate of several surface reactions, including the HF etching of SiO₂ and chemical vapor deposition (CVD) of metal oxides. These reactions requires water as a reagent or catalyst; by using DNA to control the adsorption of water on the surface, it is possible to achieve highly localized control of reaction kinetics. The inorganic nanostructures thus obtained inherents the shape of the DNA template, often with sub-20 nanometer or better lateral resolution. We also show that even a individual single-stranded DNA is capable of catalyzing the HF etching of SiO2, producing a trench that is sub-5 nm in width. These results highlight the potential of DNA nanostructure in bottom-up nanofabrication of photonic and electronic devices.

According to ITRS (2013 Edition), the Fin half-pitch of FinFET will be shrunk to 9.5nm by 2023. This aim could be reached by multi-patterning photolithography or extreme UV lithography, but the cost will be extremely high. Bottom-up patterning strategies, like directed self-assembly of block copolymer lithography, might be the more economical solutions.
Self-assembly of DNA, driven by multivalent hydrogen-bond interaction, is also an effective bottom-up approach for constructing prescribed synthetic molecular structures. By encoding spatial information into DNA sequence complementarity, this technique enables unique single-position addressability and modularity down to 2 nm, plus the scalable production of desired structures in an error-correction manner. Particularly, DNA origami coated with metals or oxides has been used as lithographic masks for shaping graphene and silicon, but the constant length of scaffold DNA strand restricts the maximal size and structural complexity of DNA origami masks and thus only sub-200 nm flat nanostructures have been etched.
Here, we present a new lithography enabled by 3D DNA brick crystal, which could realize sub-10 nm features over micron-scale patterns. The lithographic masks are synthesized through the modular assembly of DNA bricks, with product length ranging from 200 nm to 2 mu;m and thickness ranging from 10 nm to 60 nm. Direct deposition of the DNA lithographic masks onto an inorganic substrate, followed by reactive-ion etching produces diverse inorganic nanostructures with sub-10 nm features and a feature periodicity down to 12 nm (full pitch, equal to 6 nm half pitch). Such periodicity value could be further scaled to 8nm. Additionally, by programming the local thicknesses of DNA masks, we are able to produce 3D (non-planar) inorganic nano-features via one-step etching. We believe such high-resolution nanolithography will bridge the bottom-up and top-down techniques and open a new avenue for nano-fabrication.

In the view of material science, free-standing nanoparticle films are of great interest because of their importance in developing future nano-electronic devices. In this session, we introduce protein based free-standing nanoparticle monolayer films. We empolyed α-Synuclein (αS), which is an amyloidogenic self-interactive naturally occurring protein. Our protein-based approach of preparing the free-standing AuNP single-layered sheet consists of three steps. First, αS-coated AuNPs were prepared by incubating a mixture of wild-type αS and colloidal AuNPs, followed by removal of the unbound αS. The αS-AuNP conjugates were then non-covalently adsorbed onto a sacrificial layer at acidic pH. By dissolving the substrate in chloroform, the AuNP monolayer was unleashed as a free-standing. Owing to the stable protein-protein interaction, the film was successfully expanded to a 4-inch diameter sheet, which has never been achieved with any other free-standing nanoparticle monolayers. The film was highly flexible in solution, so it was able to form conformal contact with microspheres. Additionally, the monolayer film was patterned at micron-scale and unprecedented double-component nanoparticle films with specific patterns were successfully fabricated. Therefore, the protein-based ultrathin free-standing AuNP monolayer film has potentials to be applied in a wide range of nanobiotechnology including development of nano-electronic devices.

Nanoscale assembly of tunably metastable “reflectin” proteins creates high refractive index Bragg lamellae or Mie reflectors within and between specialized cells in the epithelia of certain molluscs. In squids, this assembly and the resulting coloration and brightness of reflectivity are tunable by neuronal signaling for underwater optical communication and camouflage. We discovered that signal dependent neutralization of the cationic reflectins overcomes their Coulombic repulsion, with the resulting condensation initiating secondary folding of canonically repeated domains that act as molecular Velcro-like patches to drive further tertiary and quaternary condensation and hierarchical assembly with consequent dehydration of the Bragg lamellae, thus changing the brightness and color of the reflected light. In other cells or species, this assembly is fixed, creating permanently bright, broadband (white or silver) or spectrally selective (colored) reflectivity. Among this latter group, we discovered that giant clams use Mie-scattering to redistribute solar photons to symbiotic algae living within the animal host, increasing the algae&’s photosynthetic efficiency. These discoveries are guiding the development of electrically switchable shutters for IR detectors and new geometries for higher efficiency flexible solar cells.
In contrast to these highly reflective systems, the visual system of the moth -that flies and locates food and mates by dim starlight - cannot afford to lose photons to reflection. Sub-wavelength projections covering the moth&’s eye surface provide a graded refractive index that eliminates visible reflection. Inspired by this principle, we developed a facile, scalable and generic surface modification protocol, based on colloidal lithography and plasma etching, that yields ‘moth-eye&’ anti-reflective structures on Si, Ge, GaAs and CdTe substrates and optics. Large increases in transmission, bandwidth, and omni-directional response were obtained in these nanostructured materials at mid- and far-IR wavelengths (from 5 to >50 micrometers), with performance better than commercially available interference-based coatings. Effective medium theory, transfer matrix calculations, and quantitative measurements of transmission, reflection and scattering were used to investigate how photon trajectories were affected by moth-eye geometry. Applications are readily available for IR and optical detectors, thermo-photovoltaics, glint reduction and camouflage.

Gas sensors are needed in modern applications for reliable and unobtrusive measurements. Existing gas sensors often degrade their measurement accuracy in the presence of interferences and cannot quantitate several components in complex gas mixtures. Thus, new sensing approaches are required with improved sensor selectivity. In this talk, we will present an assessment of the capabilities of natural and bio-inspired nanostructures for selective gas sensing. We will provide details of our approach for selective vapor sensing by taking advantage of the hierarchical photonic nanostructure formed in the scales of Morpho butterfly wings. Upon interactions with different vapors and mixtures of vapors, such photonic structure produces remarkably diverse differential reflectance spectra. While we have found that the response selectivity of iridescent scales of the Morpho butterfly wings dramatically outperforms existing sensors, our interest was to fabricate such structures. Upon fabrication of bio-inspired nanostructures, we have found that individual nanofabricated sensors not only selectively detect separate gases in pristine conditions but also quantify these gases in mixtures, and even when blended with a variable moisture background. We will show that while quantitation of analytes in the presence of variable backgrounds is challenging for most sensor arrays, we achieved this aspirational goal using individual bio-inspired multivariable sensors. These colorimetric sensors can be tuned for numerous gas sensing scenarios in confined areas or as individual nodes for distributed monitoring.

A wide class of classical and quantum optical devices are based on the coupling of individual atoms, molecules, quantum dots, or other emitters to the electromagnetic field of nanofabricated optical cavities. The coupling efficiency, which can be precisely simulated using numerical codes, is strongly governed by the position of the emitter within the optical modes of the device. For example, the enhancement of an emitter's fluorescence is proportional to the mode-dependent local density of optical states (LDOS) via the Purcell effect. A number of existing experimental techniques variously combine AFM, SEM, and sophisticated lithography to position single emitters within single devices but currently there is no scalable technique to deterministically position emitters within nanooptical environments. This limits our ability to make and study devices based on cavity-emitter interactions---entire papers are often based around the performance of a single, heroically-fabricated device.
Here we experimentally demonstrate the deterministic coupling of fluorescent molecules to photonic crystal nanocavities (PCC) at a large scale. Individual DNA origami molecules carrying discrete numbers of fluorescent molecules are positioned, with the resolution of e-beam lithography, in thousands of microfabricated devices. We first validated our approach by taking spectra of 21 different cavities in which each cavity featured an origami placed at a different position along the midline of the cavity. Periodic variation in the peak intensity of the emission demonstrated our ability to control emitter-cavity coupling by "walking" the origami in 50 nanometer steps through the modal pattern of the cavity. Next we used the same technique to create a complete two-dimensional map of one mode of our PCCs with 25 nanometer resolution. For each of 600 precise x-y locations within the mode, a separate device was constructed having a DNA origami at location x-y. The devices are arranged to recapitulate the x-y position of the devices at a large scale, so that simple epifluorescence microscopy creates an "image" of the LDOS. Lastly, we demonstrate the programmability and scalability of our approach by building a 3-bit 65,536 nanocavity array in which the intensity of each pixel is independently programmed by controlling the location and number of molecules within a specific nanocavity.

Natural biological structures, in particular, moth&’s eye and lotus leaf were the inspirations for the formation of low-refractive index antireflective glass film that embody omni-directional optical properties over a wide range of wavelengths, while also possessing water-repelling, or superhydrophobic, capability that holds significant potential for solar panels, lenses, detectors, architectural windows, optical components used in weapons systems and in many other products. The coatings comprise an interconnected network of nanoscale pores surrounded by a nanostructured silica framework. These structures result from a novel fabrication method that utilizes metastable spinodal phase separation in low-alkali borosilicate glass materials. The approach not only enables design of surface microstructures with graded-index antireflection characteristics, where the surface reflection is suppressed through optical impedance matching between interfaces, but also facilitates self-cleaning ability through modification of the surface chemistry. Based on near complete elimination of Fresnel reflections through a single-side coated glass and corresponding increase in broadband transmission, the fabricated nanostructured surfaces are found to promote a general and an invaluable ~ 3-7% relative increase in current output of multiple direct/indirect bandgap photovoltaic cells, while preventing dust/pollution accumulation. Moreover, these antireflective, self-cleaning surfacesdemonstrate superior resistance against mechanical wear and abrasion andcan be engineered to block ultraviolet radiation, provide antifogging as well as omniphobic functionalities. With demonstrated scalable and manufacturable formulations, providing an all-in-one combination of multiple salient and unique performance enhancers, our approach represents a conceptually fundamental basis to be developed for leading edge coated optical quality products.

We describe the synthesis, characterization, and self-assembly of bio-inspired six-tailed amphiphiles that trigger optical transformations in water-dispersed microdroplets of thermotropic liquid crystals (LCs). These synthetic amphiphiles mimic structural features of the six-tailed glycolipid component of Lipid A (a component of bacterial endotoxin) and trigger bipolar-to-radial transitions in droplets of LCs at exceedingly low (pg/mL) concentrations. This is the first synthetic amphiphile demonstrated to trigger transitions in LC droplets at these ultralow concentrations. We hypothesize that both Lipid A and these mimics trigger transitions through a process that involves the self-assembly of the amphiphiles at topological defects (boojums) in LC droplets. Our synthetic amphiphiles and Lipid A exhibit similar interfacial behaviors and sizes, and we demonstrate using SAXS that these mimics self-assemble into inverted nanostructures similar to those exhibited by Lipid A. The structures and properties of these synthetic Lipid A mimics can be tuned readily: below a critical tail length, for example, the amphiphiles do not form self-assembled nanostructures and do not trigger orientational changes in LC droplets. These observations support the conclusion that molecular architectures that promote formation of self-associated nanostructures are needed to trigger optical transitions. They also provide insight into the mechanisms through which LC droplets respond to six-tailed amphiphiles at extremely low (pg/mL) concentrations. This class of synthetic amphiphiles mimics key structural features and aspects of the self-assembly behaviour of Lipid A. The synthetic route used to design these amphiphiles permits control over architecture and molecular functionality in ways that are difficult to achieve through synthetic modifications to Lipid A, but that could be used to tune self-assembly behaviour or the nature of the interactions of self-associated nanostructures with LC droplets. We therefore anticipate that this class of bio-inspired amphiphile will open the door to the development of new and exquisitely sensitive LC-droplet based environmental sensors.

Cell lasers have potential applications in biology and medicine, including in biomolecular sensing and cytometry.[1, 2] So far, cell lasers have been realized either by using an extracellular semiconductor gain medium or by intracellular fluorescent proteins.[3-5] Fluorescent proteins were found to be an attractive option for providing optical gain in these lasers as they offer biocompatibility, high quantum yield and good photostability. However, the transfection required to trigger expression of fluorescent proteins in cells is a time-consuming process, typically taking more than 24 hours. Such long preparation times are inconvenient for applications not requiring genetically encoded gain.
In the wider context of visualizing cells and studying intracellular processes, synthetic fluorescent molecular probes that can penetrate the membrane of live cells are widely used.[6, 7] Compared to fluorescent proteins, a much greater variety of such small organic dyes is available, providing a wide range of different biochemical and spectral properties.[8] In general, these probes are detected via their fluorescence, i.e. spontaneous emission.[9] However, here we show that integrating these probes into an optical resonator turns them into an optical gain medium supporting efficient stimulated emission with distinct spectral characteristics [10]. Advantageously, this approach provides a fast and simple method to obtain lasing from normal cells within less than one hour by using a biocompatible cell-tracker dye that becomes highly fluorescent upon entering the cytoplasm, thus forming a localized gain volume. We demonstrate lasing with this approach from both spherical cells in suspension and from elongated, adherent cells grown and stained directly on one of the reflectors forming the cavity. Fluorescent dyes offer a convenient method for transforming normal cells into biolasers for a variety of applications in cell-culture and lab-on-a-chip settings.
References
[1] X. Fan, S. H. Yun, Nature Methods2014, 11, 141.
[2] M. T. Hill, M. C. Gather, Nature Photon.2014, 8, 908.
[3] P. Gourley, Nature Med.1996, 2, 942.
[4] P. L. Gourley, M.F. Gourley, Trends Biotechnol.2000, 18, 443.
[5] M. C. Gather, S. H. Yun, Nature Photon.2011, 5, 406.
[6] T. Ueno, T. Nagano, Nature Methods2011, 8, 642.
[7] R.Y. Tsien, Annu. Rev. Neurosci.1989, 12, 227.
[8] J. Zhang, R. E. Campbell, A. Y. Ting, R. Y. Tsien, Nat. Rev. Mol. Cell Biol.2002, 3, 906.
[9] J. R. Lakowicz, Principles of fluorescence spectroscopy. 2007: Springer Science & Business Media.
[10] S. Nizamoglu, K.-B. Lee, M. C. Gather, K. S. Kim, M. Jeon, S. Kim, M. Humar, and S.-H. Yun, 2015Advanced Optical Materials. doi: 10.1002/adom.201500144

When the constitutive materials of photonic crystals (PCs) are stimuli-responsive, the resultant PCs exhibit optical properties that can be tuned by the stimuli. This can thus be exploited for promising applications in colour displays, biological and chemical sensors, inks and paints, and many optically active components. However, the preparation of the required photonic structures is the first issue to be solved. In the past two decades, approaches such as microfabrication and self-assembly have been developed to incorporate stimuli-responsive materials into existing periodic structures for the fabrication of PCs, either as the initial building blocks or as the surrounding matrix. Generally, the materials that respond to thermal, pH, chemical, optical, electrical, or magnetic stimuli are either soft or aggregate, which is why the manufacture of 3D hierarchical photonic structures with responsive properties is a great challenge. Recently, inspired by biological PCs in nature which exhibit both flexible and responsive properties, researchers have developed various methods to synthesize metals and metal oxides with hierarchical structures by using a biological PC as the template. This review will focus on our recent developments in this field. In particular, PCs with biological hierarchical structures that can be tuned by external stimuli have recently been successfully fabricated. These findings offer innovative insights into the design of responsive PCs and should be of great importance for future applications of these materials.

As its name suggests, the Glasswing butterfly (Greta oto) has transparent wings with remarkable low reflectance below 5% even for large view angles [1]. This omnidirectional anti-reflection behavior is caused by nanopillars with subwavelength radii covering the transparent region of its wing membrane. In difference to the classical biological anti-reflection structures, these pillars feature a random height and width distribution. Simulating the optical properties of these structures we demonstrate that this randomness is responsible for the omnidirectional anti-reflection properties of the Glasswing butterfly. Especially, the random height distribution drastically reduces the reflection for large view angles of 80° enabling efficient camouflage by transparency during the flight of this butterfly. Based on this design principle almost perfect anti-reflection surfaces can be engineered for a broad band of wavelength and an extremely wide range of view angles. Such anti-reflective surfaces are needed for applications ranging from efficient solar cells, sensors, surface emitting lasers, LED and various opto-electronics application. Finally, we will discuss possible options to fabricate artificial replicas of these highly random nanostructures.
[1] Siddique, Gomard, Hölscher, Nat. Comm. 6, 6909 (2015)

We propose a butterfly-cornea-inspired nanoplasmonic array that provides angle-insensitive reflectance for use in optical-cavity-based implantable intraocular pressure (IOP) sensors with remote optical readout. The proposed structure can be easily fabricated on flexible membranes that form the pressure-sensing optical cavity, provides relatively flat broadband reflectivity up to ±20° from the normal incidence, and generates strong optical resonance. These properties are a must for the implementation of practical IOP sensors.
The surface of the butterfly cornea is covered with an array of nanoscale optical structures whose reflection is insensitive to angle variations up to ±60° from normal incidence. This layer is composed of a hexagonal array of nanoscale semispherical protuberances that introduce a gradual increase of refractive index and minimize reflection and angle dependence. Inspired by the geometry and optical properties of the biological structure, we designed a biomimetic plasmonic membrane (BPM) that provides an angle-insensitive reflection layer.
The core feature of our BPM is a hexagonal array (lattice constant: 300-400 nm) of gold hemispheres (radius: 120-180 nm) placed on the bottom surface of the deformable silicon-nitride membrane (inside the cavity). The top surface is in contact with saline during IOP sensing. In our study, the reflectance of the BPM becomes larger and flatter over a wider range of wavelengths as the ratio r of the radius to the lattice constant increased, while the angle-insensitivity improved as r decreased. The BPM with the largest r of 0.45 exhibited the largest reflectance (~0.92) that was very flat over the wavelength range of 700-1200 nm, with an angle insensitivity up to ±5° from normal incidence. For r = 0.4, the BPM showed the slightly reduced reflectivity (~0.8) that was flat over the wavelength range of 700-1000 nm, yet its angle insensitivity improved to ±15°. Further reduction in r down to 0.35 lowered the reflectivity to ~0.7 yet provided the best angle insensitivity up to ±20°. It is also important to mention that our BPM does not exhibit thin-film interference, and varying the thickness of the silicon-nitride membrane (0.3-1.3 µm) has a negligible effect on its reflectance profile.
We also examined the possibility of using the BPM for IOP sensing in the range of 0-40 mmHg (normal IOP: 10-20 mmHg) in simulation. Being illuminated with broadband light, the cavity formed by a 500-nm-thick PBM (r=0.45) and a silicon substrate (coated with a 50nm-thick gold layer) generated sharp, highly detectable resonances (quality factor: ~320). As the cavity gap decreased from 4.6 to 4 µm at a step of 0.1 µm (which implies step increases in the ambient pressure), the resonance peak shifted linearly from 0.8 to 0.9 µm at a step of 20 nm (linearity: 0.96). The required spectral resolution is 2.5 nm shift per 1 mmHg, which can be easily obtained using a commercially available miniature spectrometer.

The skin structure of cephalopods endows them with remarkable dynamic camouflage capabilities. Consequently, much research effort has focused on understanding and emulating these animals&’ color changing abilities in the visible region of the electromagnetic spectrum. In contrast, despite the importance of infrared signaling and detection for many industrial and military applications, few studies have attempted to translate the principles underlying cephalopod adaptive coloration to infrared camouflage. We have drawn inspiration from nanostructures implicated in cephalopods&’ camouflage abilities and developed strategies for the self-assembly of unique cephalopod structural proteins into dynamically tunable biomimetic camouflage coatings on both transparent and flexible substrates.^1,2 Our substrates can adhere to arbitrary surfaces, and their reflectance can be reversibly modulated from the visible to the near-infrared regions of the electromagnetic spectrum with both chemical and mechanical stimuli.^1,2 Thus, we can endow common objects with any shape or form factor with tunable camouflage capabilities.^1,2 Our work represents a key step toward the development of wearable biomimetic color and shapeshifting technologies for stealth applications.
Phan, L.; Walkup IV, W. G.; Ordinario, D. O.; Karshalev, E.; Jocson, J.-M.; Burke, A. M.; Gorodetsky, A. A. Adv. Mater.2013, 25, 5621-5625.
Phan, L.; Ordinario, D. O.; Karshalev, E.; Walkup IV, W. G.; Shenk, M. A.; Gorodetsky, A. A. J. Mater. Chem. C.2015, Advance Article, DOI: 10.1039/C5TC00125K.

Photonic fibers are playing a significant role in many applications where the manipulation of light is crucial, including biomedical sensing and imaging, laser surgery, white light laser devices, or communication and information processing technology. Conventional photonic fibers are fabricated by thermal drawing. This process imposes stringent requirements on the constituent materials&’ thermal and mechanical properties, thereby severely limiting the library of suitable components and ultimately restraining the resulting fiber&’s functional scope. Here, we present a novel approach for the formation of elastic, mechano-sensitive, color-tunable photonic fibers that are mimicking the structural aspects of a biological photonic system found in the blue seed coat of a tropical plant. The photonic fibers consist of an elastomeric multilayer cladding, rolled onto a stretchable core fiber at room temperature. The fibers show up to 95% transverse reflectivity. The fiber&’s reflection band can be tuned by applying an axial strain or a lateral compression. An axial elongation of initially red fibers to about twice their original length results in a shift of the reflected color via orange, yellow, and green to blue. This phenomenon is reversible and persists even after several thousand deformation cycles. Applications for the mechano-responsive, color-tunable photonic fibers include the optical sensing of mechanical deformations and stress distributions in medical and civil engineering applications, solvent vapor analyzers, dynamic textiles, and components for fiber-optic signal processing.