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 and purification, which results in low conjugation efficiency, reduced fluorescence quantum yield, and less colloidal stability. Herein, we developed a new strategy to achieve robust QD-protein conjugates with a single-step synthesis in a short time. Our strategy takes advantage of a two-cysteine/six-HisTag linkage, that are genetically encoded with the SpyCatcher protein expressed by Escherichia coli, and could be directly attached to the QD shell surface during the core/shell QD synthesis in aqueous solution. This synthetic route results in robust core/shell QD-protein conjugates that are highly stable, highly fluorescent, and versatile for a wide range of semiconductor materials with various sizes, compositions and morphologies. We further demonstrated the organization of micron-scale one-dimensional QD chain structures and related heterosystems by specific SpyCatcher-SpyTag chemistry, which is high yield, highly specific and compatible with diverse pH, temperature, and buffer in vitro and in vivo environments. Since the reactive units are conveniently introduced by genetic engineering in either prokaryotic or eukaryotic expression systems, we recognized that the SpyTag-SpyCatcher chemistry is an excellent platform for QD-proteins conjugates with tunable fluorescence properties, and could be used an ideal platform for bacterial cell directed self-assembly of functional devices in large-area. While the present work applies to QD-SpyCatcher, we expect the general applicability of our approach to other materials and recombinant proteins for scalable assembly of multiplexed functional devices.
9:00 AM - F5.16
De-Coupling Structure from Function: Controlling Hierarchal Polymer Dynamics with Bio-Inspired Metal-Coordination
Scott C. Grindy 1 Rob Learsch 1 Devin G. Barrett 2 Jing Cheng 2 Phillip B. Messersmith 2 Niels Holten-Andersen 1
1Massachusetts Institute of Technology Cambridge USA2Northwestern University Evanston USAShow Abstract
Metal-coordinate bonds inspired by the tough, ductile mussel fiber have recently been demonstrated to act as the reversible crosslinks in self-adhesive polymer hydrogels. The exchange kinetics of these crosslinks can be tuned across several orders of magnitude simply by using different transition metals as the crosslink center. Thus, with the exact same polymer, we are able to engineer materials with vastly different viscoelastic relaxation times.
We show that the individual relaxation times are modular - we can insert and remove viscoelastic relaxation modes by simply changing the relative concentrations of different transition metals in our gels. Traditionally, the polymer architecture and viscoelastic properties are interdependent, but the modularity of metal-coordination complexes allows us to effectively de-couple the polymer structure from the mechanical behavior of the system, as we can modulate the mechanical properties orthogonally from the polymer backbone. Using bio-inspired metal-coordinate complexes in this manner will allow the creation of model viscoelastic systems to explore fundamental questions in soft materials design, such as how incorporating well-controlled reversible interactions into covalent gel networks can be used to control stiffness, toughness, and ductility in hydrogel systems.
9:00 AM - F5.17
Slippery Metallic Surfaces
Alexander B. Tesler 2 1 Philsyok Kim 1 Joanna Aizenberg 2 1 3
1Harvard University Cambridge USA2Harvard University Cambridge USA3Harvard University Cambridge USAShow Abstract
A simple, nontoxic and inexpensive method to prepare mechanically robust surfaces that repels a variety of liquids and solids has immediate relevance in many industrial applications. Unwanted interactions between liquids and surfaces are currently a limiting factor nearly everywhere liquids are handled or encountered. Most state-of-the-art liquid repellent surfaces are modeled after lotus leaves, which are known to exhibit superhydrophobicity and self-cleaning. Despite over a decade of research, these surfaces are still plagued with problems that restrict their practical applications.
Recently, the slippery liquid-infused porous surfaces (SLIPS) technology was introduced by our group. SLIPS technology is inspired by the Nepenthes pitcher plant and provides unique capabilities that are unmatched by any other liquid-repellent surface technologies. SLIPS surfaces function under high pressure conditions, instantly self-heal imperfections, provide optical transparency, repel ice nucleation, and are ultra-repellent to pure and complex fluids such as blood, crude oil, and brine. They also repel solids such as ice and wax. These properties allow the slippery surfaces to be used in a wide variety of applications and environments. Moreover, the slippery surfaces can be constructed from a broad range of simple, inexpensive materials without the need for specialized fabrication facilities.
Here we used a stainless steel, which is widely used in biomedical, household and industrial equipment, surgical instruments, kitchen appliances, transport and architecture, as a substrate. We use an inexpensive and environmentally friendly electrodeposition process to form a thin layer of nanostructured tungsten bronze. Such films are mechanically robust and can be functionalized to increase its hydrophobicity, ideal for integration with SLIPS technology. Moreover, electrochemical deposition provides various control parameters for optimization of the film morphology. We will present that slippery stainless steel surfaces can be optimized to repel simple and complex fluids, reduces ice formation, accelerates frost removal and prevent adhesion of biofilms.
9:00 AM - F5.18
Experimental Design Based Analysis of Novel Poly(L-Lactic Acid) Based Nanocomposites: Relationship between Design Parameters and Compressive Properties
Samin Eftekhari 1 Ihab El Sawi 2 Ginette Turcotte 1 Habiba Bougherara 2
1Ryerson University Toronto Canada2Ryerson University Toronto CanadaShow Abstract
Biopolymer based nanocomposites are great of interest for use as bone scaffolds due to their biocompatibility and adjustable mechanical and biodegradation properties. Mechanical properties of human bone vary tremendously according to location and function (i.e., load or non-load bearing). Therefore, a scaffold's mechanical properties should be tailored to match the demands of the defect site, and to decrease or avoid complications such as stress-shielding. Scaffold properties can be tailored to the particular mechanical and physiologic demands of the host tissue by effectively controlling weight fraction, ratio of the constituents, and morphology.
Current research is focused on investigation of the effects of content parameters of recently developed nanocomposites on mechanical behavior of them were investigated by using factorial design methodology. The poly(L-lactic acid)/microcrystalline cellulose/hydroxyapatite nanoparticles nanocomposites were fabricated using sublimation of polymer solvent and leaching out the porogen out of nanocomposite structure followed by characterization using scanning electron microscopy (SEM), universal compression testing machine. Statistical analysis evaluated the effects of three independent variables on final properties of the nanocomposite. Increasing the concentration of PLLA affected mechanical properties including compressive yield and Young&’s modulus positively. Besides, the higher ratio of MCC/HA ratio (0-4) led to enhancement of compressive yield from 0.32 to 0.87 MPa and Young's modulus from 16.11 to 28.55 MPa. Furthermore, the effect of concentration of PLLA on final compressive properties has been evaluated. Based on optimization with factorial design methodology, by varying the comcentration of PLLA from 10% to 20 %, compressive yield improved from 0.87 to 1.36 MPA, and Young's modulus from 28.55 to 44.64 MPa. The same investigation has been conducted for nanocomposites with the presence of porogen. The comparissive study of nanocomposites with porogen and without porogen revealed that incorporation of porogen during the fabrication of the nanocomposite resulted lower compressive yield in compare with the ones with no porogen. However, SEM images showed that the pore shapes uniformity and interconnectivity were improved. The mechanisms involved for the failour during the compression test also have been discussed.
9:00 AM - F5.19
Self-Assembly of Catalytic Peptides to Mimic Enzymes
Yuka Kanetsuki 1 Yoshiaki Maeda 1 Nadeem Javid 2 Krystyna Duncan 2 Yasuhiro Ikezoe 1 Rein V Ulijn 2 3 Hiroshi Matsui 1
1City University of New York, Hunter College New York USA2University of Strathclyde Glasgow United Kingdom3City University of New York New York USAShow Abstract
Natural enzymes have been evolved as impressive catalysts for taking a long time. Although they have effective functions in many chemical reactions, it is difficult for researchers to optimize the functions and improve the yield of products because of the complexity and lack of fully understanding of the catalytic mechanism. In our study, to discover efficient peptide biocatalysts and evolve the catalytic functions, (i) we constructed a novel screening methodology that enables the selection of catalytic peptides from sequence libraries based on the phage display technique and (ii) we fused hydrophobic tail of amyloid β mimicking peptide (ABP)1) at the C-terminus of catalytic peptide which can provide hydrophobic part as well as self-assembling property to accumulate catalytic center. This approach using libraries of M13 phage viruses consists of 109 different phages, each displaying five copies of peptide sequence at the tip. The peptide catalysts in chemical reaction were selected via supramolecular gelation2) of targeted products on phage viruses for the mass-separated panning process. In this methodology, when a phage library is exposed to precursors in aqueous solution, the product is gelated by the activity of catalytic peptide on phages. Based on catalytic gelation combined with phage display we selected several catalytic peptides which can catalyze to bond between two molecules by amide condensation.
To confirm the generated compound by amide condensation occurred in selected peptide display region of phages, transmission electron microscopy (TEM) was carried out. The TEM images showed that the hydrogel was observed in reaction sample including selected catalytic peptide, while no such hydrogel was observed in control sample which is absence of the peptide. We also confirmed the product in the reaction sample by HPLC. In the sequences of the selected peptides, we found some of peptides contain nucleophilic amino acids and also the most common catalytic triads (histidine, serine and aspartic acid or glutamic acid). They might have not only amide condensation activity but also amide hydrolase activity because these catalytic triads are found in a range of amidases. Natural enzymes have hydrophobic pocket to capture substrates in order to enhance catalytic selectivity and activity. By addition of ABP to catalytic peptide, the catalytic activity was increased rather than without ABP peptide. The result showed that the assembly of catalytic peptides is important for evolution of catalytic function.
The discovery of these peptides for mimicking protease has significantly impact because the peptide consisting of the only 12 amino acids is useful and can be designed easier for synthesis of chemical compound such as drug molecules.
1) M. J. Krysmann, V. Castelletto, I. W. Hamley, Soft Matter, (2007), 3, 1401-1406.
2) R. J. Williams, A. M. Smith, R. Collins, N. Hodson, A.K. Das, R. V. Ulijn, Nat Nanotechnol., (2009), 4, 19-24.
9:00 AM - F5.20
Artificially Engineered Protein Hydrogels that Mimic Selective Gating by the Nuclear Pore Complex
Minkyu Kim 1 Wesley G. Chen 2 Matthew J. Glassman 1 Jeon Woong Kang 3 Katharina Ribbeck 2 Bradley D. Olsen 1
1Massachusetts Institute of Technology Cambridge USA2Massachusetts Institute of Technology Cambridge USA3Massachusetts Institute of Technology Cambridge USAShow Abstract
A polypeptide-based hydrogel fills the nuclear pore channels embedded in the nuclear membrane of a eukaryotic cell and acts as a selective gate allowing passage of less than 0.1% of all proteins in the cell while translocating over 1,000 molecules per second. The gel-forming proteins are nucleoporins, containing “FG” repeat sequences which are known to associate with one another to construct physical gels and give rise to the hydrogel&’s selective filtering property. This biologically specific selectivity of nucleoporin hydrogels, which is unprecedented in synthetic polymer gels, makes them scientifically interesting materials with a potential for broad impacts on separation technologies. However, major obstacles in utilizing nucleoporin hydrogels for advanced technology include low biosynthetic yield of the natural protein; long gel processing time, delaying immediate use; and incomplete knowledge of sequence-structure property-function relationships of the nucleoporin hydrogel due to the complexity of natural protein sequences, hindering creating tunable selective filters.
Herein, we report for the first time artificially engineered protein hydrogels that mimic the selective permeability of nucleoporin hydrogels, are produced in high yields, and possess reduced gelation times. Analysis of a well-investigated nucleoporin, Nsp1, yielded a pair of consensus sequences for a 19 amino acid nucleoporin repeat which is repeated 16 times in the native protein with extremely high consensus at each position except one. This fundamental repeat unit was cloned into an artificial protein polymer by ligating 16 such units in a row to produce a nucleoporin-like protein (NLP). To facilitate hydrogel formation, NLP sequences were flanked with coiled-coil domains as endblocks of NLPs, creating three dimensional polymer networks.
Simplified NLP sequences allowed investigation of the sequence-structure property-function relationships of nucleoporin hydrogels. Using a combination of techniques including the hydrogel inversion test, selective transport assay, shear rheology, and Raman spectroscopy, we found that only recombinant NLPs with coiled-coil endblocks constructed hydrogels with different levels of selective permeability. A pair of NLPs with a single amino acid replacement within the repeat unit presented significantly different amounts of cargo transportation into the hydrogels and hydrogel relaxation times, suggesting that physicochemical properties of NLP sequences are correlated with the selective permeability and mechanical properties of the hydrogels. Moreover, our findings revealed that not only “FG” sequences but also other sequences of natural nucleoporins would be important for gel structure and the selective filtering function. Tunable mechanical properties and selective permeability of nucleoporin-mimicking hydrogels with high yields can potentially advance the technology in drug delivery, food toxicology, and defense applications.
9:00 AM - F5.21
Inhibition of Gram-Positive and Gram-Negative Bacteria Growth on Selenium Nanoparticle Coated Paper Towels
Qi Wang 1 Thomas Webster 2
1Northeastern University Boston USA2Northeastern University Boston USAShow Abstract
Wide spread bacteria contamination has been found on various paper products, such as paper towels hanging in sink splash zones or those used to clean surfaces, filter papers used in water and air purifying systems, and wrapping used in the food industry, which may lead to the potential spread of bacteria and consequent health concerns. Due to the porous structure of fibers in all paper products, such materials are prone to bacteria growth and, thus, are sources for continual contamination. Besides, this porous structure provides an environment that favors the attachment of bacteria and makes it more difficult to kill bacteria once forming a biofilm. One of the most promising approaches towards preventing infections is coating paper products with antimicrobial materials. Therefore, in this study, selenium nanoparticles were coated on normal paper towel surfaces through a quick precipitation method, introducing antibacterial properties to the paper towels. Their effectiveness at preventing biofilm formation was tested in bacterial assays involving Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Staphylococcus epidermidis. The results showed that there were significant and continuous bacteria inhibition with about a 90% reduction from 24 to 72 hours for gram-positive bacteria including S. aureus and S. epidermidis. The selenium coated paper towels also showed significant inhibition of gram-negative bacteria like P. aeruginosa and E. coli growth at about 57% and 84%, respectively, after 72 hours of treatment. Therefore, this study suggested that coating paper products with selenium nanoparticles may be an effective way to decrease various gram-positive and gram-negative bacteria growth on paper products, which might be used for potentially important applications for antimicrobial purposes in the food packaging industry and in clinical environments.
9:00 AM - F5.22
Dopa-Incorporated Recombinant Mussel Bioadhesives with Highly Enhanced Adhesion and Water-Resistance
Byeongseon Yang 1 Dooyup Jung 1 Niraikulam Ayyadurai 5 Hyungdon Yun 3 Yoo Seong Choi 4 Qingye Lu 2 Hongbo Zeng 2 Byeong Hee Hwang 1 Hyung Joon Cha 1
1Pohang University of Science and Technology Pohang Korea (the Republic of)2University of Alberta Edmonton Canada3Konkuk University Seoul Korea (the Republic of)4Chungnam National University Daejeon Korea (the Republic of)5Yeungnam University Gyeongsan Korea (the Republic of)Show Abstract
3,4-Dihydroxyphenylalanine (Dopa), which is a hydroxylated form of the tyrosine residue, has been suggested to be a key factor for rapid and strong underwater adhesion through its mediation of various interactions, such as bidentate hydrogen bonding, complexes with metals and metal oxides, the cation-pi interaction, and oxidative cross-linking, because it is oxidised to Dopa-quinone. Mussel adhesive proteins (MAPs) are one of examples where Dopa chemistry is the core of their underwater adhesion with extremely high Dopa contents of ~10-25 mol%. The biosynthesis of recombinant MAPs in an Escherichia coli system was a good approach to overcome the availability limitation that results from the extremely low yield of natural extraction of MAPs from mussel feet and to apply MAPs as an universal underwater bioadhesive. However, Dopa incorporation always follows as the biggest problem because lack of Dopa in recombinant MAPs critically limited the underwater adhesion. To transform tyrosine residues into Dopa molecules, an in vitro mushroom tyrosinase treatment has commonly been conducted. However, this process exhibits a low (<~15%) modification yield. Here, we explore the in vivo residue-specific incorporation of Dopa into recombinant MAPs. Because Dopa molecules can be misaminoacylated to tRNATyr by endogenous tyrosyl-tRNA synthetase, the quantitative replacement of tyrosine residues by Dopa was achieved with a yield of over ~90 % via an in vivo residue-specific incorporation strategy, to create, for the first time, engineered mussel adhesive proteins (MAPs) in E. coli with a very high Dopa content close to that of natural MAPs. Using several analyses, we confirmed that Dopa-incorporated engineered recombinant MAPs exhibited the superior surface adhesion and water-resistance abilities by assistance of Dopa-mediated interactions including oxidative Dopa cross-linking. In addition, their underwater adhesive properties were comparable to those of natural MAPs. Our results show their great potential as bioglues for use in practical underwater applications.
9:00 AM - F5.23
Sea Anemone Minicollagen: Molecular Structure, Properties, and Nature-Mimicking Recombinant Production
Dooyup Jung 1 Yun Jung Yang 1 Jeong Hyun Seo 2 Yoo Seong Choi 3 Byeong Hee Hwang 1 Hyung Joon Cha 1
1Pohang University of Science and Technology Pohang Korea (the Republic of)2Yeungnam University Gyeongsan Korea (the Republic of)3Chungnam National University Daejeon Korea (the Republic of)Show Abstract
Aquatic species in the Phylum Cnidaria, including sea anemone and jellyfish, have special cell organelle called nematocyst. When stimulated, with waving motion of tentacles, coiled tubular structure in charged nematocyst is instantaneously stretches out to capture prey or keep the organism itself from predators. The driving force of this ultra-speedy discharge is high osmotic pressure maintained in charged nematocyst. Therefore, the capsule wall of nematocyst should be tough enough to withstand this internal pressure. Previous researches have shown that minicollagen is a main component of capsule wall, so it can be thought as critical structural material to meet mechanical requirement. However, almost every research treating minicollagen and its experimental analysis has used Hydra as a source organism. In the present work, estuarine sea anemone Nematostella vectensis was chosen as a novel target organism for minicollagen research. Structural analysis found disulfide crosslinking and triple helix formation among minicollagens, which are regarded as main reason of superior mechanical toughness. Measuring mechanical properties of nematocyst capsule wall were also tried to know how exactly strong the wall is. Forming a part applying this nature-inspired structure and power in engineering, recombinant production of sea anemone minicollagen in Escherichia coli expression system was successfully endeavored. Genetically redesigned E. coli for disulfide bond formation and in vivo incorporation of 4-hydroxyproline was used to mimic natural structure of minicollagen. These approaches cannot only help researchers to acquire homogenous minicollagen for basic analysis, but also suggest its possibility as a plentiful biomaterial in engineering.
9:00 AM - F5.24
Photo-Crosslinked Silk-Like Protein Derived from Sea Anemone for Hydrogel-Based Scaffold Fabrication
Yun Jung Yang 1 Yoo Seong Choi 2 Dooyup Jung 1 Hyung Joon Cha 1
1POSTECH Pohang Korea (the Republic of)2Chungnam National University Daejeon Korea (the Republic of)Show Abstract
Gel-based scaffolds have been utilized as space filling agents, delivery vehicles, and three dimensional structures. However, their weak strength and stiffness (elastic modulus) were considered as limitations to endure physiological stimulus. Here, we exploited recombinant silk-like protein (aneroin), originally derived from sea anemone&’s tentacle, as tough gel material. Aneroin consists of decamer repeats and has similar secondary structure of an elastic silk from spider (flagelliform silk). Photo-initiated crosslinking was tried for hydrogel formation. Additionally, disulfide crosslink was also carried out to enhance mechanical property of gel. We found that elastic modulus of aneroin was three times higher than skeletal muscle, and its strength was two-fold stronger than cardiac muscle. In addition to mechanical properties, photo-crosslinked aneroin showed high transmittance in visible light. Thus, durable and transparent aneroin hydrogel would be expanded its applications to biomolecular carrier as well as structural support.
9:00 AM - F5.25
Virus-Based Piezoelectric Energy Generation
Seung-Wuk Lee 1 2 Kwang Heo 1 2
1University of California, Berkeley Berkeley USA2Lawrence Berkeley National Laboratory Berkeley USAShow Abstract
Piezoelectric materials can convert mechanical energy into electrical energy, and piezoelectric devices made of various inorganic materials and organic polymers have been demonstrated. However, synthesizing such materials often requires toxic materials, harsh conditions and/or complex procedures. Recently, it was shown that hierarchically organized natural materials, such as bones, collagen fibrils and peptide nanotubes, can display piezoelectric properties. In my presentation, I will show our innovative approach to produce virus-based piezoelectric energy generation. Recently, we establish that the piezoelectric and liquid crystalline properties of M13 bacteriophage (phage) can be used to generate electrical energy. Using piezoresponse force microscopy, we characterize the structure-dependent piezoelectric properties of phage at the molecular level. We then show that self-assembled thin films of phage can exhibit piezoelectric strengths of up to 7.8 pm/V. We also demonstrate that it is possible to modulate the dipole strength of phage, and hence tune their piezoelectric response by genetically engineering the phage&’s major coat proteins. Finally, we develop a phage-based piezoelectric generator that produces up to 6 nA of current and 400 mV of potential, and use it to operate a liquid crystal display. Because biotechnology techniques enable large-scale production of genetically modified phages, phage-based piezoelectric materials potentially offer a simple and environment-friendly approach to piezoelectricity generation.
9:00 AM - F5.26
Proangiogenic Multi-Domain Peptide Hydrogels
Vivek Ashok Kumar 1 Nichole L Taylor 1 Abhishek Jalan 1 Benjamin K Wang 1 Siyu Shi 1 Jeffrey D Hartgerink 1
1Rice University Houston USAShow Abstract
Multidomain peptides (MDP) self-assemble into extracellular matrix mimetic nanofibrous hydrogels. These short chain biocompatible matrices, exhibit shear thinning and rapid recovery, allowing for syringe aspiration and directed in situ delivery. Tailoring of terminal residues allows for fined tuned control of molecular, cellular and tissue responses. In this study, we show the development of a hybrid MDP capable of stimulating robust angiogenic responses. A short chain (15 amino acid) peptide sequenced from VEGF 165 was conjugated to a 16 amino acid MDP. Mechanical and ultrastructural characterization showed presence of nanofibrous structure, shear thinning and recovery. Biological function was demonstrated by upregulation of VEGFR1, VEGFR2 and NP-1 activation. Cytocompatibility with HUVEC and hMSCs showed similar cell adhesion, proliferation and scratch wound healing to positive controls. Gross morphology of subcutaneous implants of injectable hydrogels showed large vessels in and around implants, without the development of hemangiomas or leaky vasculature. Histomorphometric analysis showed rapid cellular infiltration as early as 3 days, rapid development of stable blood vessels as early as 7 days suggesting formation of mature blood vessels. These vessels subsequently resorb by 3 weeks. Materials developed in this study may allow for rapid angiogenesis, increased ischemic tissue perfusion, and augmented tissue regeneration.