Lara Estroff, Cornell University
Seung-Wuk Lee, University of California, Berkeley
Jwa-Min Nam, Seoul National University
Edward Perkins, U. S. Army Corps of Engineers
Symposium Support National Science Foundation
F3: Peptide and Protein Assembly I
Monday PM, December 01, 2014
Sheraton, 2nd Floor, Independence West
2:30 AM - *F3.01
Multi-Stimuli Responsive Polypeptides and Block Copolypeptide Assemblies
Timothy Deming 1 2 Jessica Kramer 2
1UCLA Los Angeles USA2UCLA Los Angeles USAShow Abstract
We have developed synthetic methods that allow incorporation of unprecedented levels of functionality into polypeptide materials. We report on the design and properties of stimuli responsive polypeptide motifs that are able to respond differently to different individual stimuli, such as redox, temperature, or enzymes. These materials allow multimodal switching of polypeptide properties to obtain desirable features, such as coupled responses to multiple external inputs. The reversible, multiresponsive nature of these polypeptides makes them particularly attractive as components in molecular devices or nanoscale assemblies capable of sequential, or triggered, responses to different stimuli, akin to switches capable of performing Boolean-like operations. We will describe how these motifs can be incorporated into self-assembled materials such as vesicles and hydrogels.
3:00 AM - *F3.02
Peptide-Based Hollow Spherical Nanoparticle Superstructures: Syntheses, Structures, and Emergent Properties
Nathaniel Rosi 1
1University of Pittsburgh Pittsburgh USAShow Abstract
Carefully designed peptide conjugate molecules are used to direct the synthesis and assembly of a diverse class of ‘hollow&’ spherical nanoparticle superstructures. In this talk, we describe the design of these structures, with particular emphasis on methods for controlling sphere diameter and composition. In addition, we discuss several unique emergent properties of these materials, ways in which these properties can be tuned, and how these properties enable cargo storage and release applications.
3:30 AM - F3.03
Self-Assembled Suprastructures from Recombinant Oleosin
Daniel A Hammer 1 Kevin B Vargo 1 Gao Chen 1 Ranganath Parthsarathy 1 Eric Wang 2 Paul Heiney 3
1University of Pennsylvania Philadelphia USA2University of Pennsylvania Philadelphia USA3University of Pennsylvania Philadelphia USAShow Abstract
The self-assembly of suprastructures from recombinant amphiphilic proteins would allow precise control over surfactant chemistry and the facile incorporation of biological functionality. We used cryo-TEM to confirm self-assembled structures from recombinantly-produced mutants of the naturally-occurring sunflower protein, oleosin (1). Oleosin is an amphilphilic protein with two hydrophilic blocks separated by an interior hydrophobic block with a proline knot that causes the folding of the protein into the shape of a “U.” We studied the phase behavior of a subset of truncation mutants of the wild-type molecule, as a function of solution ionic strength and protein hydrophilic fraction, observing nanometric fibers, sheets, and vesicles. Vesicle membrane thickness correlated with increasing hydrophilic fraction for a fixed hydrophobic domain length. The existence of a bilayer membrane was corroborated in giant vesicles through the localized encapsulation of hydrophobic Nile red and hydrophilic calcein. Circular dichroism revealed that changes in nanostructure morphology in this family of mutants were unrelated to changes in secondary structure.
We further modified the protein in a variety of ways - removing structure from the internal hydrophobic component and adding less bulky residues to the hydrophobic core. This family of molecules are surfactants that form spherical micelles (as measured by DLS, cryo-TEM and X-ray scattering) and have a low CMC. Using recombinant methods, we have also incorporated bio-functionality into these proteins, including receptor binding peptide and affibodies, protease cleavable domains, biotinylation, and temperature dependent switches. Ultimately, we envision using recombinant techniques to introduce novel functionality into these materials toward numerous biological applications and the construction of responsive, self-assembled soft matter.
K. B. Vargo, R.Parthasarathy and D. A. Hammer. Proceedings of the National Academy of Sciences USA109, 11657-11662 (2012).
3:45 AM - F3.04
Targeting Collagen Strands by Triple Helical Hybridization
Michael Yu 1
1University of Utah Salt Lake City USAShow Abstract
Collagen, the most abundant protein in mammals, plays a crucial role in tissue development and regeneration, and its structural and metabolic abnormalities are associated with debilitating genetic diseases and numerous pathologic conditions. The ability to target collagens in diseased tissue could lead to new diagnostics and therapeutics, as well as applications in regenerative medicine. In this talk, I will present a new collagen targeting strategy that is based on triple helical hybridization between denatured collagen strands (of diseased tissues) and synthetic collagen mimetic peptide (CMP). This hybridization results in robust collagen specific binding in vivo which allows detection of degraded collagens present in normal tissues undergoing fast remodeling (e.g. bones and cartilage) and those in diseased tissues with persistent wound healing activity (e.g. tumor, fibrosis). I will describe various experiments designed to elucidate the mechanism of the hybridization as well as those verifying the CMP&’s collagen binding capacity both in vitro and in vivo. This is an entirely new way to target the microenvironment of malignant tissues and could lead to new opportunity for management of numerous pathologic conditions associated with high collagen degradation and remodeling activity.
F4: Peptide and Protein Assembly II
Monday PM, December 01, 2014
Sheraton, 2nd Floor, Independence West
4:30 AM - *F4.01
Syntax of ldquo;Smartrdquo; Peptide Polymers Governs Their Function
Ashutosh Chilkoti 1
1Duke University Durham USAShow Abstract
“Smart” polymers that respond to stimuli in their aqueous environments with a pronounced physical change are of great utility in biotechnology and medicine. Currently, however, only few peptide polymers show this behavior. Here, we uncover the relationship between the syntax of peptide polymers and their lower critical solution temperature (LCST) transition behavior as well as a class of peptide polymers that show the reverse -upper critical solution temperature (UCST)- behavior. I will show that the syntax of these functional peptide polymers ranges from polymers composed of simple repeats of a few amino acids to those whose syntax resembles the complex non-repetitive syntax of protein domains, and that the concept of syntax can be deployed to re-program bioactive peptides to exhibit dual functions, as seen by their stimulus responsiveness and biological activity. The unique linguistic features exhibited by these peptide polymers suggests that peptide polymers can be best described as linear macromolecules that are composed of amino acid “letters” that are organized as “words”, with higher order organization of one or more words that repeat or recur to create a “phrase” (the macromolecule) and postulate that the syntax -word order- of this class of polymers controls their function. Hence, by analogy to syntax in natural language —defined as the arrangement of words in a phrase that controls its meaning, I will introduce new concept -syntactomers- to describe polymers whose properties are controlled by their organization as a collection of letters into words and the higher order organization of words into functional phrases.
5:00 AM - *F4.02
Predicting Protein Biomaterial Functions from Protein Designs: Interfacing Experimental and Modeling Approaches
David L. Kaplan 1 Joyce Wong 2 Markus Buehler 3
1Tufts University Medford USA2Boston University Boston USA3MIT Cambridge USAShow Abstract
Designing protein-based biomaterials with specific functional properties is desirable for fundamental interest as well as for applied needs such as medical devices, scaffolding in regenerative medicine and drug delivery. To improve predictability of biomaterials function, multiple parameters in protein polymer design need to be considered, including sequence chemistry, molecular weight and domain distribution. Concurrent with the experimental design of such protein polymers, appropriate mathematical models are needed to predict how the engineered polymers will self-organize at different length scales with consideration for structural hierarchy to relate to material functions. The importance of multi-scale bioengineering and the combined use of modeling and experiment in advancing designs of biomaterials will be the focus of the talk. This is an emerging field where modeling can inform polymer design and vice versa. The approaches being pursued in protein-polymer design and bioengineering, polymer processing and modeling/predictions of function will be described as an example on how this iterative approach can be used to broaden predictive structure-function relationships in the field.
5:30 AM - *F4.03
Biotemplating of Bimetallic Nanoparticles Using Self-Assembled Protein Scaffolds and TEThER Peptides
Sarah Heilshorn 1
1Stanford University Stanford USAShow Abstract
The use of biological scaffolds to template inorganic material offers unique strategies to synthesize precise composite nanostructures of different sizes, shapes, and compositions. Proteins are unique biological scaffolds that consist of multiple binding regions, or epitope sites, that site-specifically associate with conserved amino acid sequences within protein binding partners. These binding regions can be exploited as synthesis sites for multiple inorganic species within the same protein scaffold, resulting in bimetallic inorganic nanostructures. We demonstrate this strategy with the scaffold protein clathrin, which self-assembles into spherical cages. Specifically we design tether peptides that noncovalently associate with distinct clathrin epitope sites while initiating simultaneous synthesis of two inorganic species on the assembled clathrin protein cage. We demonstrate the versatility of this unique biotemplating strategy by synthesizing two types of composite structures, silver-gold mixed bimetallic nanoparticles and silver-gold core-shell nanostructures, from a single clathrin template. This noncovalent, Template Engineering Through Epitope Recognition, or TEThER, strategy can be readily applied to any protein assembly with known epitope sites to template a variety of bimetallic structures without the need for chemical or genetic modifications.
F1: DNA Nanostructure and Assembly I
Monday AM, December 01, 2014
Sheraton, 2nd Floor, Independence West
9:00 AM - *F1.01
The Nature of the DNA Bond
Chad A. Mirkin 1
1Northwestern University Evanston USAShow Abstract
For decades the biological roles of nucleic acids as catalytic enzymes, intracellular regulatory molecules, and as the carriers of genetic information have been studied extensively. More recently, the sequence-specific binding properties of DNA that make it so ubiquitous among all living systems have been hijacked to direct the assembly of materials at the nanoscale. In such cases, it has become useful to consider the DNA as an artificial bond that facilitates nearly infinite tailorability in the interactions between nanomaterials via bond (i.e. oligonucleotide) length, strength, orthogonality, and even directionality. Although this powerful concept can be applied in variety of contexts including DNA tiles, origami scaffolds, and supramolecular constructs, here we explore the use of rigid inorganic nanoparticles functionalized with DNA that act to orient oligonucleotides perpendicular to their surfaces to dictate DNA bonding interactions. By elucidating a series of design rules for the nature of these DNA bonds, we show the construction of nanoparticle superlattices with over 20 different crystal symmetries with precise control over particle size and spacing. In some cases, these materials can be prepared so that they form large single crystalline domains with a well-defined crystal habit indicative of the minimum energy Wulff polyhedron of the parent superlattice. Finally, we show opportunities for dynamic and reconfigurable superlattices facilitated by the unique properties of the DNA bond.
F5: Poster Session: Reverse Engineering of Bioinspired Nanomaterials
Monday PM, December 01, 2014
Hynes, Level 1, Hall B
9:00 AM - F5.01
Using Nano-Carbons to Promote Collagen Fibril Alignment
Emily C Green 1 Dilinazi Aishanjiang 1 Yiying Zhang 1 Marilyn L Minus 1
1Northeastern University Boston USAShow Abstract
Due to the rigid-rod characteristics of carbon nanotubes (CNT) they have been shown to aide and induce atomic and nano-scale ordering of polymer materials. In this work, this CNT trait is exploited to understand its potential along with other rigid nano-carbons to promote ordered assembly of biological materials. For the synthetic formation of collagen materials highly aligned collagen fibrils are necessary in order to replicate the native collagen structure in bone, tendon, and ligaments. This study also allows for fundamental understanding regarding collagen self-assembly. The ability to form highly aligned collagen fibrils may also lead to new fiber processing methods to enable in the development of novel applications for collagenous materials. In this work collagen fibers were self-assembled in the presence of both single-wall carbon nanotubes (SWNT) and carbon nano-chips (CNC) using a gel-spinning approach. The morphology and dispersion quality of the nano-carbons was found to play a significant role in the overall collagen fibril alignment. Small-angle X-ray Scattering (SAXS) analysis shows that low concentrations (0.5 wt%) of well-dispersed SWNT promote collagen molecular alignment leading to banding structure similar to native collagen. Fiber morphology was analyzed by both Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Beyond ordering, the nano-carbons used were also able to reinforce the collagen composite fibers. Mechanical property characterization showed a considerable increase in both strength and elastic modulus (100% and 122%, respectively), as compared to control fibers. This work is the first to show direct evidence that nano-carbon fillers may promote collagen molecular and fibril alignment during self-assembly processes.
9:00 AM - F5.02
Cage-Shaped Proteins Assisted Carbon Nanotubes Synthesis for Dye-Sensitized Solar Cells
Ippei Inoue 1 Kenichi Toyoda 2 Yasuaki Ishikawa 2 Hisashi Yasueda 1 Ichiro Yamashita 2 Yukiharu Uraoka 2
1Ajinomoto Co., Inc. Kawasaki Japan2Nara Institute of Science and Technology Ikoma JapanShow Abstract
Carbon-nanotubes (CNTs) are one of the most promising nano-materials and have been applied for various nano-electric devices, such as solar cells, batteries, and sensors, due to their superb physical properties, chemical inertness and excellent electron conductivity. One of the most basic issues in CNTs synthesis is a control of CNTs diameter and quality, since variations of CNTs cause dispersion of device characteristics. To address the issue, there have been many reports on a CNTs synthesis using catalysts of iron nanoparticles which were produced utilizing physicochemical and biological approaches.
In this presentation, we report a novel method for synthesis of diameter controlled multi-walled CNTs (MWNTs) by utilizing two-kinds of biomineralized iron nanoparticles as catalysts for chemical vapor deposition (CVD). The iron nanoparticles were 7 nm and 4.5 nm in diameter and were produced by utilizing cage-shaped proteins, ferritin and Dps, respectively. The two kinds of protein had silicon-binding peptide aptamers and could carry iron nanoparticles onto a surface of silicon substrate. Diameters of the MWNTs could be controlled in a range of 5-10 nm by the ratio of two kinds of the proteins. Structures of MWNTs were essentially maintained even at 600°C in atmospheric air. A weight loss peak of thermo-gravimetric analysis appeared at 678°C corresponds to a loss of 63 wt% which was attributable to the MWNTs themselves. We applied the thin MWNTs to electrodes of dye-sensitized solar cells (DSSCs). The MWNTs were coated with TiO2 by biomineralizing activity of a genetically modified Dps. The TiO2-coated MWNT improved an electric resistance of a DSSC photoelectrode. As a result, the power conversion efficiency of the DSSC with the protein-templated TiO2-MWNT was enhanced from 5.8% to 6.6%. Moreover, the MWNTs were able to be applied for counter electrodes instead of rare metal Pt. Those results indicated that the thin MWNTs can be used as an excellent material for solar cells.
9:00 AM - F5.03
Fabrication of Discrete Protein Polygons for Multivalent Display of Functional Proteins in Defined Nanostructures
Young Eun Kim 1 Yongwon Jung 1
1Korea Advanced Institute of Science and Technology Daejeon Korea (the Republic of)Show Abstract
Proteins have recently attracted much attention as a building block for supramolecular structures due to their functional diversity as well as biocompatible and biodegradable properties. Several strategies for the construction of protein nanostructures including nanowires, nanotubes and nanorings have been described [1-4]. These approaches were based on the specific molecular recognition such as metal ion-protein, enzyme-inhibitor and protein-protein interaction . Although various sophisticated structures of protein have been developed, the design of protein supramolecular structures is still challenging because of the structural complexity of proteins. Herein, we presented the fabrication of highly discrete protein polygons from cellular self-assembles of green fluorescent protein (GFP). The rationally designed GFP monomer is expressed in cell, and it undergoes the cellular self-assembly into polymeric forms of protein, thereby offering a highly simple and versatile way to prepare protein polymers. Furthermore, these protein polygons could be functionalized through introduction of the desired ligand into either N-terminus or C-terminus of a monomer protein using genetic manipulation. Notably, GFP polygons from dimer to decamer were individually purified, indicating that these GFP polygons can display the exact number of ligands. Finally, we showed that fabrication of discrete GFP polygons depending on the valency of functional proteins.
. R. Matsunaga, S. Yanaka, S. Nagatoishi, K. Tsumoto Nat Commun. 4 (2013)
. TF.Chou, C. So, BR. White, JC. Carlson, M. Sarikaya, CR. Wagner ACS Nano 2, 12 (2008)
. ER. Ballster, AH. Lai, RN. Zuckermann, Y. Cheng, JD. Mougous Proc Natl Acad Sci U S A. 105, 10 (2008)
. K. Oohora, A. Onoda, T. Hayashi Chem Commun., 48 (2012)
9:00 AM - F5.04
Preparation of Structural Colored Colloidal Amorphous Arrays by Layer-by-Layer Deposition
Masanori Iwata 1 Yukikazu Takeoka 1 Takahiro Seki 1 Shinya Yoshioka 2
1Nagoya University Nagoya Japan2Osaka University Suita JapanShow Abstract
Recently, structural colored materials attract many researchers&’ attention as environmentally friendly color materials. Structural color is observed in the materials that have the microstructures comparable to the wavelength of visible light. We can obtain brightly colored materials, without any toxic dyes or pigments, by utilizing structural colored materials. There exist so many informative examples in living things for making artificial structural colored materials. In this paper, we describe the preparation of structural colored materials imitating the bird&’s feather that displays an angle-independent structural color.
Here, we have an interest in a blue bird, Steller&’s jay. This bird&’s feather contains the amorphous structure of air cavities in keratin matrix (spongy layer) above the assembly of melanin granules, and reveals an angle-independent bright blue structural color. However, an amelanotic Steller&’s jay&’s feather having the same type of spongy layer displays a white color due to the lack of melanin granules. This fact indicates that the brightly structural colored materials having amorphous structure require the existence of a black background.
Therefore, for making artificial angle-independent structural colored materials, we prepared the membranous colloidal amorphous arrays of mono-dispersed submicron-sized silica particles (SiO2 thin films) on a black quartz glass substrate by Layer-by-Layer (LbL) deposition technique that enables us to control the film thickness of SiO2 thin films.
For LbL deposition, we employed a cationic polyelectrolyte, poly(diallyldimethylammonium chloride) (PDDA) (MW = 400,000-500,000), and silica particles of 190 nm in diameter of which surface was negatively charged. First, a black quartz glass substrate with negative charges was dipped into PDDA aqueous solution (0.2 wt%) for 10 min, followed by rinsing with water. Then, the substrate was dipped into the silica particles aqueous suspension (10 wt%, containing NaCl 0.02 M) for 10 min, followed by washing. We defined these operations as one cycle and prepared SiO2 thin films by varying the number of repeating times of the cycle.
Symmetrical and circular pattern around origin in two-dimensional fast-Fourier transform power spectrum of the scanning electron microscope (SEM) image on the surface of the resultant SiO2 thin film confirmed that silica particles formed isotropic amorphous array with short-range order. From the results of the SEM observations on the SiO2 thin films with various thicknesses, we found that the thickness was directly proportional to the number of repeating times of the cycle. Additionally, the saturation of the structural color from the SiO2 thin films was decreased when using a clear glass plate as a substrate.
In summary, we succeeded to prepare the structural colored materials imitating the feather of the blue bird by depositing mono-dispersed submicron-sized silica particles with short-range order on a black substrate.
9:00 AM - F5.05
Hydrogels Containing Biomimetic Topographical Features for Small Intestinal Model Systems
Megha Kamath 2 1 Abigail N Koppes 2 Rebecca Carrier 2
1Northeastern University Boston USA2Northeastern University Boston USAShow Abstract
There is an urgent need for improved cultured intestinal models for studying oral drug delivery and intestinal disease, or to serve as a potential treatment for short bowel syndrome (SBS). Common intestinal epithelial culture models are 2-dimensional, which limit the understanding of cell behavior in their natural environment. However, native small intestinal tissue consists of multi-scale structures, such as crypts and villi, as well as extra-cellular matrix (ECM) that play an important role in aiding cellular growth and impacting cellular phenotype. To this end, we have developed a method that allows for the growth of Caco-2 in a monolayer on substrates mimicking the natural topography of the small intestinal tract. Using replica molding of PDMS, we obtained biomimetic collagen-I hydrogel substrates that showed enhanced growth of epithelial cells. This system will contribute to a better understanding of the growth of intestinal cells and eventually to efficient drug delivery in the GI for various disorders.
Porcine small intestinal tissue was washed, fixed, sectioned and placed in 0.1%OsO4 in 0.1M PBS (4 °C, 72 hours) followed by agitation to remove the epithelial cells. Samples were rinsed, dehydrated in ethanol, critically point dried (CPD) and silanized. A thin layer of PDMS (10:1 v:v) was applied on the tissue and baked for 2 hours at 60°C, and separated with via differential swelling in TEA. Positive bovine collagen-I replicas were solution cast on PDMS molds and allowed to gel at 37°C for 2-3 hours. Caco-2 cells were seeded at a density of 76,000 cells/mL and grown for 8 days. Fluorescence microscopy images were taken at day 8 to capture cell behavior on the replica and flat controls. To image the collagen gels, they were fixed, ethanol dehydrated and CPD. The dried gels were sputter coated with platinum and imaged using a Field Emission Scanning Electron Microscope (FE-SEM).
SEM images show that negative PDMS crypt-villi structures exhibit similar size features compared to native intestinal tissue, ranging from millimeter macrofolds to hundreds of micron villus protrusions. The CPD collagen gels have similar micro-scale size features compared to the native intestinal tissue, but there was a loss in height of villus-like structures due to dehydration and heat processing of the hydrogels for SEM. The hydrogels provided environmental and topographical cues, allowing seeded cells to proliferate and mature. Fluorescence microscopy images show that Caco-2 grown on the porous collagen replicas formed monolayers and exhibit a 3.8-fold increase in proliferation compared to flat controls that remained subconfluent after 8 days in culture. Ongoing studies involve characterizing the hydrogel surface topography to understand and quantify Caco-2 and primary intestinal stem cell behavior on these biomimetic materials. This model will serve as stepping-stone to enhance drug delivery as well as play a crucial role in regenerative medicine.
9:00 AM - F5.06
Apoferritin Encapsulated Rare Earth Luminescent Nanoparticles
Hideyuki Yoshimura 1
1Meiji University Kawasaki JapanShow Abstract
Luminescent europium (Eu) and dysprosium (Dy) doped Yttrium-Vanadate (Y-V) nanoparticles (NPs) were synthesized in a cavity of the protein, apoferritin. The use of inorganic nanoparticles (NPs), instead of organic dyes, is becoming popular for molecular labeling because of their strong resistance to photobleaching. Since structure of protein is strictly regulated by DNA, the size of NPs in the protein also becomes homogeneous. Moreover, apoferritin is thermally stable water soluble protein, and thus encapsulated NPs are also stably dispersed in aqueous solution. The sequence of a protein can be modified by protein engineering to enable the protein to bind to a specific molecule, e.g. an aptamer, these NPs are likely to be biocompatible and would have significant potential for biological imaging applications.
Y-V NPs were synthesized by incubating a solution of apoferritin with Y3+ and VO3- ions in the presence of ethylene diamine-N-N'-diacetic acid (EDDA). EDDA plays an important role in preventing Y-vanadate precipitation in bulk solution by chelating the Y3+ ions. Using high resolution electron microscopy, the obtained NPs in the apoferritin cavities were confirmed to be amorphous, and to consist of Y and V. The average size of the obtained NPs was 6.6 ± 0.7 nm.
Eu-doped Y-V (Y-V:Eu) NPs were synthesized by the same procedure as Y-V NPs, except that Eu(NO3)3 was added. Y-V:Eu NPs exhibited a strong absorption peak due to the O-V charge transfer transition and remarkable luminescence at 618 nm due to the 5D0 - 7F2 transition. Luminescence showed maximum intensity at Eu doping ratio of 11.4%. Strong red luminescence was easily observed by eye, even in a brightly lit room.
It is known that O-H vibrations play a dominant role in the non-radiative transition from excited Eu3+ ions and that transition is greatly reduced by substituting hydrogen (H) to deuterium (D). To investigate the non-radiative transition pathway of Y:Eu and Y-V:Eu NPs, the luminescence lifetime of these NPs in water (H2O) and heavy water (D2O) were compared. The lifetime difference in H2O solution and D2O solution is six times larger in Y:Eu than Y-V:Eu NPs at low Eu concentration. This means non-radiative transition due to the O-H vibration is smaller in Y-V:Eu NPs. Accordingly, Y-V NPs showed strong luminescence compared to Y:Eu NPs which we reported previously . Dy-doped Y-V (Y-V:Dy) NPs were also synthesized in apoferritin cavities and showed luminescence peaks at 482 nm and 572 nm, corresponding to 4F9/2 - 6H15/2 and 4F9/2 - 6H13/2 transitions. Luminescence showed maximum intensity at Dy doping ratio of 3.5%. This solution had a yellow color under UV irradiation.
 T. Harada and H. Yoshimura, J. Appl. Phys, 114, 044309 (2013).
9:00 AM - F5.07
A Dip-Stick Colorimetric Sensor Based on Morphological Changes of Plasmonic Nanoparticles
Brian Malile 1
1York University Toronto CanadaShow Abstract
There is a constant need for economical and portable point-of-care biodiagnoistic devices. Numerous colorimetric sensors are based on the aggregation of plasmonic nanoparticles; however, colloidal solutions present limitations on the portability of the sensor. We present a new sensing platform in which the colorimetric signal comes from changes in the morphology of substrate-bound nanoparticles. The sensing platform consists of immobilized gold-coated silver nanoparticles on a glass substrate, on top of which a stimulus-responsive polyelectrolyte-aptamer film is assembled. Binding of the target to the aptamer leads to the swelling of the polyelectrolyte layer as conferred by ellipsometry, and results in an increase in the diffusion rate of etchant molecules. The etchant changes the size and shape of the nanoparticles and therefore the colour or intensity of the film. We achieve a discernible colorimetric difference between the control film and the target bound film, and investigate the concentration dependence and effects of interference species. Characterization techniques such as ellipsometry and cyclic voltammetry will help to advance the understanding of the mechanisms involved. Further development of this platform may provide facile field analysis by using consumer electronics in addition to presenting new opportunities for aptamer-based sensing.
9:00 AM - F5.08
Engineered Phage Based Matrix Stiffness Modulating Osteogenic Differentiation
Hee-Sook Lee 3 2 Kwang Heo 3 So Young Yoo 1 Seung-Wuk Lee 3
1Pusan National University School of Medicine Yangsan Korea (the Republic of)2Ministry of Food and Drug Safety Busan Korea (the Republic of)3University of California, Berkeley Berkeley USAShow Abstract
Although it is known that specific biochemical cues in tissue extracellular matrices (ECM) play a critical role in regulating cellular growth processes and their fate, the role of physical cues of them such as stiffness in guiding the fate of resident stem cells has not been well studied so far. In this study, we have demonstrated engineered phage mediated matrix controlling stiffness for various applications over conventional tissue engineering materials by exploiting its physical and biological structural features (such as the phage&’s self-assembling, selfreplicating and evolving nature). We modified M13 phages to express biotin-like peptides (HPQ) and/or integrin binding peptides (RGD) on their major and minor coat proteins. The stiffness of matrix was controlled by cross-linking the engineered phage with different concentarions and compositions of streptavidin and polymer mixture. Then, we verified that osteogenic differentiation could be controlled according to the rates of stiffness of the constructed phage matrix. Osteogenic gene expressions through mRNA expression quantification and protein activity assays showed that they were specifically increased when bone stem cells were cultured on the M13 matrix with adequate stiffness. Our phage matrices, which can be easily functionalized with various ligands and growth factors to enhance the stiffness modulation using other chemicals, may be used as a convenient tissue matrice platforms for controlling stem cell expansion and differentiation. [This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (2013R1A1A3008484)]
9:00 AM - F5.09
Bioinspired Templates for Nucleation and Growth of Polydopamine during Melanogenesis
Luke Klosterman 1 Christopher Bettinger 1
1Carnegie Mellon University Pittsburgh USAShow Abstract
Melanins are a class of pigments with unique physicochemical properties including redox activity, hybrid ionic conductivity, and efficient photon-phonon conversion. Natural eumelanins and synthetic analogs, termed “polydopamine”, have garnered interest in applications including clean energy, functional interfaces, and biomedicine. However, the structural distinctions between natural and synthetic melanins remain elusive. Parsing out these structural deviations is essential in advancing the use of these materials. Here we present a study in which bioinspired surface chemistries are modulated to elucidate the adsorption and deposition of polydopamine precursors.
We have investigated the effect of fundamentally simple differences in surface chemistries on the growth of polydopamine films. Silicon dioxide and self-assembled monolayers of amino, aromatic, or aliphatic moietes produce melanin films with comparable thickness (ca. 10nm) and morphology of adherent islands. Electrostatically neutral aromatic and aliphatic surfaces produce smoother polydopamine films (RRMS= 0.3-0.7nm) compared to anionic oxide and cationic amine-terminated surface chemistries (RRMS= 1.1-1.6nm). Additionally, catechol dissociation at higher pH prevents film formation on the oxide and reduces the average roughness of the amine-terminated surface to a value similar to the aromatic and aliphatic (RRMS= 1.2nm at pH 8 vs. 0.5nm at pH 10). This suggests multiple modes of adsorption that provide polydopamine with its versatile coating capability. These findings are supported by quartz crystal microbalance studies.
These findings have also been extended to understand the nucleation and growth of melanins on Pmel17 template proteins on two-dimensional surfaces. Taken together, these data suggest that two-dimensional SAMs monolayers are an accurate model to replicate aspects of natural melanin synthesis. These findings will aid in elucidating the fundamental mechanisms of in vivo melanogenesis
9:00 AM - F5.10
Power Generation and Water Savings Using Water-Responsive Materials
Ahmet-Hamdi Cavusoglu 3 Xi Chen 2 Ozgur Sahin 2 1
1Columbia University New York USA2Columbia University New York USA3Columbia University New York USAShow Abstract
Water-responsive materials swell and shrink in response to changes in relative humidity (RH) and can be potentially used to harvest energy from evaporating water . Here, we investigated the potential of harvesting energy from naturally evaporating water due to typical weather conditions across the United States. We modeled the power output, the effect on evaporation rate, and the intermittency of the power output. We first performed steady state calculations over a range of 218 locations across the United States and determined the average energy flux and net water savings due to a reduction in evaporation rates. We then used a non-steady state mass and energy balance approach on three test locations of South-East NY, Western TX, and South-East CA to determine daily and yearly variations in power output. Our calculations show that this system can deliver power densities surpassing wind power and comparable to current installed solar systems. These results suggest that further research into water-responsive materials and devices can provide major benefits in developing a novel renewable energy platform.
1. X. Chen, L. Mahadevan, A. Driks, and O. Sahin. Bacillus spores as building blocks for stimuli-responsive materials and nanogenerators. Nature Nanotechnology, 2014. 9(2): p. 137-141.
9:00 AM - F5.11
Controlled Synthesis and Therapeutic Applications of Plasmonic Core-Petal Nanostructures
Amit Kumar 1 Jwa-Min Nam 1
1Seoul National University Seoul Korea (the Republic of)Show Abstract
Metal nanostructures with highly branched morphologies are an interesting and useful new class of nanomaterials due to their plasmonically enhanced optical properties, large surface area and potential as catalytic substrates. In particular, surface plasmon-derived photo-induced therapeutic effect and catalysis are highly dependent on their surface nanostructures, but the control of their branching structures is challenging. Here, we introduce a strategy for the controlled synthesis of plasmonic core-petal nanostructures (CPNs) with highly branched morphologies. The fine nanostructural engineering of CPNs was facilitated by oxidative disassembly of organic biopolymer-corona around spherical Au nanoparticles and successive anisotropic growth of Au nanopetals. We show that CPNs can act as multifunctional nanoreactors that induce protrusion-dependent controllable photodynamic and photothermal dual therapeutic effects as well as ROS generation. NIR laser-activated CPNs can be used to induce the effective destruction of cancer cells via the synergistic combination of benign plasmonic hyperthermia (~42 °C) and ROS-mediated oxidative intracellular damage. It was also shown that CPNs exhibit very strong surface-enhanced Raman scattering (SERS) signals, and this allows for post-mortem probing of ROS-mediated oxidative structural modifications of DNA that could be responsible for the apoptotic fate of cancer cells. Here, we have showcased the well-tunable synergistic plasmon-based catalytic and thermoplasmonic properties of NIR active branched nanostructures for organic photosensitizer-free bimodal photodynamic-photothermal therapeutic ablation of cancer cells. Synthesis of such biocompatible, non-invasive and aesthetic but highly effective nanotherapeutic platforms have great potential for future clinical applications.
9:00 AM - F5.12
Core-Satellite Nanostructures as SERS Bioimaging Probes for Oxidative and Nitrosative Stresses in Living Cells
Sumit Kumar 1 Jwa-Min Nam 1
1Seoul National University Seoul Korea (the Republic of)Show Abstract
Understanding the role of endogenous or exogenous reactive oxygen species (ROS) and reactive nitrogen species (RNS) at molecular, cellular, and organismal level in a range of physiological processes as well as in the pathogenesis of many diseases, is an emerging area of research in redox chemical biology. ROS and RNS often exhibit interdependent production and roles in the complex signal transduction and oxidative pathways; and sometimes direct the activation of distinct signaling mechanisms determining cell fate. Simultaneous and distinguishable monitoring of ROS and RNS is crucial to understanding their biochemistry and effects on signal transduction pathways. Surface-enhanced Raman scattering (SERS)-based biosensing probes have advantages such as highly sensitive molecular finger-printing, multiplexing and non-invasiveness for in-vitro and in-vivo applications. Here, we designed a ‘core-satellite&’ plasmonic nano-assembly with a sub-nanometer thick insulating molecular spacer between core and satellites for functionalization of heme protein. Intense SERS signals corresponding to characteristic Raman bands of Fe-porphyrin reporter moieties located in ‘hot-spot&’ junctions could be obtained due to extensive plasmonic coupling among core and satellite AuNPs. Our SERS probe was found to be highly sensitive towards exposure of ROS and RNS as distinct Raman signals were produced in both the cases. Biological experiments revealed facile internalization of core-shell bioprobes in the living cells and excellent biocompatibility. Finally, we were able to quantitatively and distinctly monitor ROS and RNS in normal and cancer cells using our SERS bioprobes. This method enables sophisticated hot plasmonic assemblies to be used for unraveling the etiology and pathophysiology of many diseases involving alterations of oxidative and nitrosative stress, such as cancer, neurological disorders, pancreatic malfunction, and inflammatory diseases.
9:00 AM - F5.13
Characterization of MgO Nanoparticles as Antibacterial Materials for Orthopedic Tissue Engineering
Daniel J. Hickey 1 Thomas J. Webster 1
1Northeastern University Boston USAShow Abstract
Regeneration of complex orthopedic tissues (such as ligaments, bones, and the tendon-to-bone insertion site) is problematic due to a lack of suitable biomaterials with the appropriate chemical and mechanical properties to elicit the formation of tissues with similar structure, organization, and functionality to natural tissues. Additionally, a non-trivial fraction of implanted biomaterials become infected by bacteria, which can lead to implant failure, secondary surgeries, and the spread of infection to other tissues throughout the body. To address these issues, the current study investigated magnesium oxide (MgO) nanoparticles as novel materials to improve orthopedic tissue regeneration and reduce bacterial infection.
Here, MgO nanoparticles and hydroxyapatite (HA) nanoparticles were dispersed within poly (l-lactic acid) (PLLA) composites and then tested for their mechanical properties, surface roughness, antibacterial properties, and their ability to support the adhesion and proliferation of fibroblasts and osteoblasts. Free nanoparticles (MgO and HA) in solution were also exposed to cells and bacteria to characterize the nature of the cellular responses to these materials.
Results showed that MgO nanoparticles in solution enhanced fibroblast and osteoblast proliferation, suggesting that magnesium plays an important role in improving cell functions. When dispersed within PLLA composites, MgO nanoparticles improved osteoblast and fibroblast adhesion and proliferation compared to plain PLLA. Osteoblasts proliferated best on nanocomposites containing both HA and MgO nanoparticles, as MgO nanoparticles were believed to enhance the osteogenic properties of HA nanoparticles. Nanocomposites containing both HA and MgO nanoparticles also exhibited the most suitable mechanical properties for application within cancellous bone. Bacterial experiments with Staphylococcus aureus showed that MgO nanoparticles exhibit powerful bactericidal efficacy, suggesting that MgO nanoparticles should be incorporated into scaffolds for orthopedic tissue engineering to improve cell functions and reduce the risk of bacterial infection.
9:00 AM - F5.14
Preparation of Mussel-Inspired Nano Scale Polymer Particle Platforms for Anchoring Inorganic NPs under High Salt Concentration Conditions
Hiroki Satoh 1 Masaaki Kanahara 1 Yuta Saito 1 Takeshi Higuchi 2 Hiroshi Yabu 2 3
1Graduate School of Engineering Tohoku University Sendai Japan2IMRAM Tohoku University Sendai Japan3JST-PRESTO Sendai JapanShow Abstract
Organic-inorganic composite particles have attracted much interest due to applications in photonics, electronics and biotechnologies. Especially the applications in biotechnologies, such as contrast agents in magnetic resonance imaging (MRI), drug carriers, heat generators for hyperthermia therapy and so on, are considered to be important in recent years. Organic-inorganic composite particles usually have been prepared by attaching inorganic NPs on polymer particles via electrostatic interaction named heterocoagulation. But since the electrostatic interaction is sensitive for environment of dispersion, the inorganic NPs easily detach from polymer particles at in vivo condition. Therefore preparation of polymer particle platforms for anchoring inorganic NPs stably even in vivo conditions is required.
To prepare that kind of polymer platforms, a catechol group is one of the good candidates. The catechol group is found in the adhesive protein of mussels and high adhesive properties of catechol groups onto many kinds of substrates have been reported. We have reported a synthesis of amphiphilic copolymer containing the catechol group and a simple preparation method of polymer particles by evaporating a good solvent from a polymer solution containing a poor solvent(SORP).
In this report, we show preparation of polymer particles containing catechol groups by using SORP. We found that these particles are successfully anchoring inorganic NPs stably under high salt concentration conditions.
The amphiphilic copolymer containing a catechol group was synthesized from dopamine methacrylamide and N-dodecylacrylamide by free radical polymerization(Polymer 1). Polymer 1 and polystyrene(PS) were respectively dissolved in tetrahydrofuran (THF) to prepare 1 g L-1 solution. A solution of Polymer 1 (0.5 mL) and that of PS (0.5 mL) were mixed, and then MilliQ membrane filtered water (1 mL) was added to the mixed solution with stirring. THF was evaporated at 25 °C in a water bath. Polymer particles of hydroxy terminated PS (PSOH) were prepared by the same method. Aqueous dispersion of Au NPs was mixed with aqueous dispersion of polymer particles, and then the mixtures were kept at 25 #8451; in a water bath. An aqueous solution of potassium chloride(2M) was added into the mixtures. The mixtures were dialyzed over night and observed by scanning electron microscopy (SEM).
SEM images showed that the AuNPs were attached homogeneously to the surface of the polymer particles containing catechol groups. On the other hand, the aggregated AuNPs were observed on the surface of the PSOH particles and on the grid. These results indicate that catechol groups were localized at the surface of polymer particles and contributed to immobilization of inorganic NPs. We succeeded in preparing polymer particles comprised of PS and amphiphilic copolymers containing catechol groups, and they succeeded in anchoring inorganic NPs stably under high salt concentration conditions.
9:00 AM - F5.15
One-Step Conjugation of Recombinant Proteins to Semiconductor Nanocrystals for Scalable Assembly of Functional Devices
Zhengtao Deng 1 Timothy K. Lu 1
1Massachusetts Institute of Technology Cambridge USAShow Abstract
Colloidal semiconductor nanocrystals, such as quantum dots (QDs), have fascinating physical properties of relevance to biology include high fluorescence quantum yield, narrow and symmetric photoluminescence spectra, broad absorption profiles, remarkable chemical, photonic, and colloidal stability, large effective Stokes shift, and high multiphoton excitation cross sections. The successful conjugation of quantum dots with biological molecules, such as proteins and DNA, is a critical step for their utility as fluorescent bio-probes, engineered biosensors, photodynamic therapy agents or sensitizers, and bio-inspired functional materials for light harvesting. Over the past 15 years, there have been continuous efforts to develop new QD-protein conjugation methods. Among them, carbodiimide crosslinker chemistry, such as 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) /N-Hydroxysuccinimide (NHS), is often used to attach QDs with proteins, typically by amide bond formation between terminal carboxyls on the QD ligands and ubiquitous amines on proteins. However, the presence of the same ubiquitous target groups on target proteins means that this approach can often result in uncontrolled heterogeneous orientation and valence on the QD and undesirable cross-linking. Furthermore, QD conjugates formed with this chemistry require multi-step synthesis an