Poster Presentations: Biomaterials - The University … Presentations: Biomaterials. 12. th. National Graduate Research Polymer Conference 2016 | College of Polymer Science and Polymer

Poster Presentations: Biomaterials

12th National Graduate Research Polymer Conference 2016 | College of Polymer Science and Polymer Engineering at The University of Akron

Chemically modified cellulose derivatives are used in coatings, adhesives, explosives, and more,

but their appearance in electronic devices and information technologies is lackluster. Cellulose

coupled with semiconducting polymers has great potential as highly flexible, functional

electronic material. Previous work has shown that cellulose filter papers can act as scaffolds for

surface functionalization using aryl-aryl coupling reactions. In this study, we synthesized a

semiconducting cellulosed-based material from 2-bromo-9,9-dihexyl-7-acetylene fluorene

polymers grafted from cellulose nanocrystals (CNC) chemically modified with 4-bromobenzoyl

chloride. The resulting materials were characterized using IR, UV-vis, fluorescence

spectroscopy, XPS, AFM, and microscopy to determine degree of functionalization as well as

optical and electrical properties. We then show the use of this material as a conductive

nanopaper for electronic applications.

Authors: Kenneth Carter, Allen ChangUniversity of Massachusetts Amherst

1



In situ nanofiller formation in polymer nanocomposites

Barbara DeButts1, Laura E. Hanzly2, and Justin R. Barone1,2* 1Macromolecules Innovations Institute, 2Biological Systems Engineering, Virginia Tech, 301D

HABB1, Blacksburg, VA 24061

*author to whom correspondence should be addressed: Email: [email protected]; Phone: (540)

231-0680

Abstract

Dispersion of nanofillers in polymer nanocomposites is problematic because nanofillers prefer to

agglomerate. Attempts to disperse nanofillers using extrusion require expensive processing

agents, as well as high heat and shear conditions that significantly add to the cost. Despite these

issues, extrusion compounding of nanofillers in polymers is the preferred method to process

nanocomposites. An “in situ polymerization” can be used to create nanocomposites, in which

the nanofillers are dispersed in monomers, followed by a polymerization reaction. However, this

technique is only realistic for a very limited number of polymers. Here, in situ nanofiller

formation is demonstrated where the nanofiller forms in the polymer matrix. Protein molecules

are dispersed in a polymer matrix, then self-assemble into a nanostructure called an amyloid.

Amyloids can be considered highly “crystalline” due to high beta sheet content. The amyloid

nanostructure has the potential for high rigidity, therefore, the potential to make high

performance nanocomposites exists.

2

mailto:[email protected]



THE UNIVERSITY OF AKRON Department of Polymer Science

12th National Graduate Research Polymer Conference

June 19-21, 2016 Goodyear Polymer Center

Oxime Hydrogels with Tunable Mechanical Properties for Tissue

Engineering Applications

Rodger Dilla1, Zachary Zander1, Clinton Weiner2, Bryan Vogt2, Matthew Becker1

1Department of Polymer Science, The University of Akron 2Department of Polymer Engineering, The University of Akron

Abstract

Hydrogels are excellent candidates for tissue engineering applications as a consequence of their network structure, ease of functionalization with biological cues, and degradation properties.1 Additionally, human mesenchymal stem cells (hMSCs) have demonstrated specific lineage commitment in response to hydrogel scaffolds with varying mechanical moduli.2,3 However, currently there have been no reported hydrogel systems that demonstrate varying moduli without changing precursor concentration, identity or stoichiometry. In this study, PEG-oxime hydrogels with tunable moduli (~5-30 kPa) were synthesized with the same precursor weight percent, stoichiometry, and concentration by varying the pH and buffer strength of the gelation solution, exploiting the kinetics of oxime bond formation.4 These results were probed extensively with small-angle oscillatory shear (SAOS) rheology, equilibrium gel-swelling experiments, and small-angle neutron scattering (SANS). Furthermore, by incorporation of an alkene-functionalized chain extender, post-polymerization modification via thiol-ene “click” addition of a FITC-peptide conjugate was achieved. This system is currently being explored for its cyto-compatibility and influence on hMSC differentiation, as well as further insight into its structure-property relationships. References: (1) Langer, R.; Vacanti, J. P. Science 1993, 260, 920–926. (2) Engler, A. J.; Sen, S.; Sweeney, H. L.; Discher, D. E. Cell 2006, 126 (4), 677–689. (3) McBeath, R.; Pirone, D. M.; Nelson, C. M.; Bhadriraju, K.; Chen, C. S. Dev. Cell 2004, 6

(4), 483–495. (4) Zander, Z. K.; Hua, G.; Wiener, C. G.; Vogt, B. D.; Becker, M. L. 2015, 1–6.

3



Determination of the effects of stereospecific glycopolymer hydrogel network architectures on water

content, structure, and hydration/dehydration profiles

April L. Fogel1, Sarah E. Morgan1

1The University of Southern Mississippi

School of Polymers and High Performance Materials 118 College Drive, #5050

Hattiesburg, MS 39406

Abstract: Hydrogels are capable of absorbing many times their weight in water but are insoluble

in water due to the crosslinked nature, making them ideal materials for use in biomedical

applications such as drug delivery systems. Water within hydrogel networks play a pivotal role in

dictating network properties such as mechanical stability, permeability, and network architecture.

Three discrete states of water (bound, restricted, and free) exist within hydrogel networks, which

are described by the degree of hydrogen bonding that occurs between molecular water and the

network. As shown in the schematic, bound water is tightly held to the network often undergoing

3 to 4 modes of hydrogen bonding, restricted water is loosely held undergoing 1 to 2 modes of

hydrogen bonding and free water is unassociated with the network. The purpose of this study is to

gain a fundamental understanding of the influence of structural parameters on water uptake,

morphology, and hydration/dehydration behavior for acrylamide based glycopolymer hydrogels

containing stereospecific glucose and galactose pendant moieties, synthesized via UV initiated

free radical polymerization. A full factorial experimental design was utilized to systematically

elucidate the influence of monomer concentration and crosslinker to monomer ratio on water

uptake and structure characterized via thermogravimetric analysis, TGA, and DSC. Adsorption

and desorption behavior was monitored via DVS.

Hydration

Dehydrated state

Structural water distribution

in hydrated state

4



Synthesis and Self-Assembly of Poly(ethylene glycol)-b-Poly(caprolactone) Micelles Using

Cyclic and Linear Poly(ethylene glycol) Architectures

Gladys Montenegro, Abegel Freedman, and Dr. Coleen Pugh*

Department of Polymer Science

The University of Akron

Akron, Ohio 44325-3909

A significant development in the drug delivery field was the conjugation of poly(ethylene

glycol) monomethyl ether (mPEG) to therapeutic proteins, which consistently increased blood

circulation time and achieved controlled therapeutic release profiles. Specific improvements in

pharmacokinetic parameters include increased blood circulation half-life as a result of decreased

elimination through immunological responses, renal excretion, and hepatic filtration.1 The

therapeutic potential conferred by PEGylation has resulted in its ubiquitous use in the drug

delivery field. However, while mPEG reduces elimination, it is not infallible. Dams et al.

discovered that the rate of elimination significantly increased with subsequent doses of

PEGylated liposomes.2 The Yokoyama group found that this phenomenon also extended to

PEGylated micelles.3 This phenomenon has been attributed to an immunological response;

specifically, anti-PEG immunoglobulin M (IgM) antibody production is stimulated during the

first dose, which activates the complement system upon subsequent doses.4,5 Knowing the

complement system can be activated by hydrophobic patches on the surface of a particle,6 we

have removed the mPEG’s methyl end groups by utilizing a cyclic PEG architecture in an

amphiphilic block-copolymer micelle assembly. This poster presents the synthesis, micellization,

and characterization of cyclic PEG-b-poly(caprolactone) and its linear analogue.

References

(1) Harris, J. M.; Chess, R. B. Nat. Rev. Drug Discov. 2003, 2, 214–221.

(2) Dams, E. T.; Laverman, P.; Oyen, W. J.; Storm, G.; Scherphof, G. L.; van Der Meer, J.

W.; Corstens, F. H.; Boerman, O. C. J. Pharmacol. Exp. Ther. 2000, 292, 1071–1079.

(3) Koide, H.; Asai, T.; Hatanaka, K.; Urakami, T.; Ishii, T.; Kenjo, E.; Nishihara, M.;

Yokoyama, M.; Ishida, T.; Kiwada, H.; Oku, N. Int. J. Pharm. 2008, 362, 197–200.

(4) Abu Lila, A. S.; Ichihara, M.; Shimizu, T.; Ishida, T.; Kiwada, H. Biol. Pharm. Bull. 2013,

36, 1842–1848.

(5) Abu Lila, A. S.; Kiwada, H.; Ishida, T. J. Control. Release 2013, 172, 38–47.

(6) Salvador-morales, C.; Sim, R. B. In Handbook of Immunological Properties of

Engineered Nanomaterials; 2013; pp. 357–384.

5



Increased Monomer Content of Acrylate-Based Shape Memory Polymers (SMPs) Increases Endothelial Cell Attachment on SMP Surfaces

Tina Govindarajan, Robin Shandas Department of Bioengineering, University of Colorado-Denver, Anschutz Medical Campus, Bioscience 2, 12705 E. Montview Ave., Suite 100, Aurora, CO 80045-7109

Increased understanding of interactions between polymer surfaces and cells has paved the way toward expanding the application of polymers to medical devices that require healthy cell-surface interactions for optimal in vivo performance. Over the last decade, we have adapted bulk characteristics of acrylate-based shape memory polymers (SMPs) and have deployed these in a number of minimally invasive device applications. While thermomechanical and bulk properties of these materials have been investigated extensively, surface properties, which govern cell attachment, have been explored less. Surface properties can be manipulated, via surface modification, to tailor these materials to achieve a specific purpose, such as endothelialization of the surface to minimize thrombotic response. By encouraging endothelial cell attachment on the surface of SMP devices, we should be able to facilitate the expansion of these materials for use in cardiovascular stents and other blood-contacting devices. In this work, we investigate the effect of changing the chemistry of the SMP on endothelial cell attachment. Nine different formulations were fabricated by changing the weight percent ratio of the monomer, tert-Butyl acrylate (tBA), with respect to the crosslinker, poly (ethylene glycol) dimethacrylate (PEGDMA). The surface characteristics quantified were wettability, obtained from contact angle measurements, and surface roughness, quantified using the roughness coefficient (Ra) from atomic force microscopy (AFM). We found that increasing the acrylate monomer content, which results in rougher, more hydrophobic surfaces, leads to increased endothelial cell attachment on SMP surfaces. Successful SMP formulations had high cell viability, visualized using Live/Dead assay as well as increased cell metabolism, quantified by increased reduction of non-fluorescent resazurin into fluorescent resofurin, both of which were visualized using fluorescent techniques. Increased understanding of surface issues for these acrylate-based SMPs may help these materials become viable options for use in cardiovascular devices.

6



An Investigation on the Use of Chitosan for Donor-site Wound

Dressings. Jiantao HUANG, Martin W. KING

College of Textiles, North Carolina State University, Raleigh, NC, 27695

Burn wounds are one of the leading accidental injuries around the world, and they often make

use of donor-site skin autografts harvested from the patients themselves. Such surgical

procedures create another type of injury called a donor-site wound. From a nursing or clinical

management perspective, there does not appear to be a standardized procedure for treating donor

site wounds. Sometimes they are treated in the same way as burn wounds, although the wound

etiologies are completely different. From a previous survey undertaken by our research group,

we have concluded that pain-relief, a non-adherent dressing, the prevention of wound desiccation,

as well as antibacterial and hemostatic properties are the major desirable features faced by the

healthcare team when managing donor site wounds. Chitosan is a derivative of chitin, and is

known to contribute to its antibacterial performance and hemocompatibility. As for the structure

of a dressing material, it is believed that a thin foam structure will obviously not release any

fibers into the wound. It will allow the exudate to penetrate into the structure and keep the wound

moist, so the wound will be non-adherent and the porous structure will be gas-permeable. So

with these ideal characteristics it is now feasible to investigate the use of chitosan foam as a

possible dressing material for donor-site wounds.

Samples of porous chitosan or chitosan foam were prepared by three different controlled freezing

methods and lyophilization of the chitosan solutions. The morphology and porosity of these foam

dressings has been evaluated and compared with commercial SilverClear and Hemcon dressings

in terms of their porosity and antibacterial performance against the Streptomycetes micro-

organism. Fibroblast cell proliferation and the hemostatic properties have been measured and

shown to depend on the method of freeze-drying. Further work will continue evaluating the

wound dressing using animal and clinical trials.

JH/MWK/20160315

7



Production of monodispersepolyacrylamide nanoparticles usingChemtor fiber reactor with high throughput

Sumit Jamkhindikar1, Dr. Holly Stretz1 and Dr. John Massingill Jr.2,

(1) Department of Chemical Engineering, Tennessee Technological University, Cookeville, TN, (2) CHEMTOR, L.P., San Marcos, TX

Use of microfluidic flow regimes for large scale production of nanoparticles is important in the emerging fields of personalized and targeted drug delivery, fuel cell catalysis, LEDs, environmental remediation of spills, etc. Formulation of droplets with uniform diameters is a challenge which microfluidic devices have been reported to achieve. Thus microfluidics could be used to produce nanoparticles for drug delivery, but the throughput is inherently low. The overall goal of the present research is to scale capillary flows to a high throughput system using a patented Chemtor fiber technology. The fluid mechanics of such environments have been studied as a model system in a microfluidic “T” junction apparatus for production of polyacrylamide nanoparticles. By the laboratory fiber reactor, monodisperse polyacrylamide nanoparticles with high through-put were produced- 662.4 gm per day throughput documented. Furthermore, the size of the produced polyacrylamide nanoparticles was around 117 nm with a polydispersity index of around 0.3. Polyacrylamide nanoparticles produced in a batch process were comparable in terms of size and distribution. Particle size distributions were measured using dynamic light scattering analysis.

8



Functionalization of hyaluronan as a tumor model for glioblastoma

Akanksha Kanitkar1*, Scott S. Verbridge1 and Timothy E. Long2 1Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA 2Department of Chemistry, Virginia Tech, Blacksburg, VA

Hyaluronan (HA), a naturally occurring glycosaminoglycan (GAG), is one of the most widely

studied biomaterials for applications ranging from tissue engineering to disease modeling. It is

one of the primary components of the mammalian extracellular matrix (ECM), consisting of two

alternating units, β-1,4-D-glucuronic acid and β-1,3-N-acetyl-D-glucosamine. Hydrogel scaffolds

of unmodified and derivatized HA have been commonly employed for wound healing, localized

drug and DNA delivery, and a variety of clinical applications owing to its biocompatibility,

viscoelastic properties and the ease of functionalization. HA molecular weight (low vs. high) has

implications in glioblastoma growth and proliferation, and our research aims at developing

biomimetic ECM mimics of normal and tumorous brain tissue. HA can be modified through

chemical crosslinking to tune its physical and biological properties to provide mechanically and

chemically robust materials. Our current research focuses on chemical modification of the primary

hydroxyl group on the HA repeat unit using methacrylic anhydride with subsequent photo-curing

reaction in the presence of a water-soluble photoinitiator (Irgacure 2959) and suitable co-monomer

such as hydroxyethyl methacrylate (HEMA). We have successfully demonstrated the introduction

of methacrylic anhydride to hyaluronic acid using a well-documented synthetic strategy. We

demonstrated that cross-linking density has a profound influence over the resulting modulus of

HA gel and an effect on tumor cell growth and proliferation.

* [email protected]

9




12th National Graduate Research Polymer Conferences


Synthetic Methods to Generate and Functionalize 3D Printed Scaffolds

Alex P. Kleinfehn, Yuanyuan Luo, Brian Fitch, Matthew L. Becker

ABSTRACT

More than half a million people require bone defect repairs in the United States annually, however, there is a deficiency in treatment options available for those whom have suffered a traumatic bone injury. One goal of bone tissue engineering is to create materials to help facilitate the regeneration of critical size bone defects of an inch or larger, but this faces significant challenges and limitations.1 The first problem limiting innovation in this area is the lack of resorbable materials for clinical use. Available materials are limited and do not offer reliable degradation time frames in wound healing environments. A second barrier is the lack of materials that can be fabricated by 3D printing with the necessary resolutions for patient configurations.

Herein, we are addressing these deficiencies using a well-studied, biodegradable polymer, poly(propylene fumarate) (PPF). PPF is an unsaturated polyester that is currently being studied for its use in bone and tissue scaffolds.2 Using a ring-opening polymerization method, PPF material with low molecular mass and a narrow molecular mass dispersity (ÐM) can be generated.3 Fine control of these properties enables the tuning of viscosity and polymer degradation, leading to reliable fabrication and resorption.

Our preliminary studies have demonstrated that kilogram size batches of biodegradable PPF with narrow ÐM can be fabricated into solid cured tissue engineering scaffolds with precise mechanical and consistent resorption properties. Our studies also show that porous scaffolds can be 3D printed at extremely high resolution.4 Cell studies have shown that printed scaffolds are nontoxic to fibroblast cells, and we seek to functionalize printed scaffolds with peptides to yield a directed cell response.

References

1. Amini, A.; Laurencin, C.; Nukavarapu, S. Crit. Rev. Biomed. Eng., 2012, 40, 363-408.

2. Wang, S.; Lu, L.; Yaszemski, M. Biomacromolecules, 2006, 7, 1976-1982. 3. Diccio, A.; Coates, G. J. Am. Chem. Soc., 2011, 133, 10724-10727. 4. Luo, Y.; Dolder, C.; Walker, J.; Mishra, R.; Dean, D.; Becker, M.

Biomacromolecules, 2016, 7, 690-697.

10



Radiopaque, Iodine Functionalized Phenylalanine-based

Poly(ester urea)s

Shan Li,† Jiayi Yu,† Mary Beth Wade,† Gina M. Policastro,† and Matthew L. Becker*,†‡

†Department of Polymer Science, The University of Akron, Akron, Ohio 44325

‡Department of Biomedical Engineering, The University of Akron, Akron, Ohio 44325

The synthesis and characterization of iodine-functionalized phenylalanine-based poly(ester

urea)s (PEUs) are reported. 4-Iodo-L-phenylalanine and L-phenylalanine were separately

reacted with 1,6-hexanediol to produce two monomers, bis-4-I-L-phenylalanine-1,6-hexanediol-

diester (1-IPHE-6 monomer) and bis-L-phenylalanine-1,6-hexanediol-diester (1-PHE-6

monomer). By varying the feed ratio of the 1-IPHE-6 and 1-PHE-6 monomers, the copolymer

composition was modulated resulting in a wide variation in thermal, mechanical and radiopacity

properties. Micro-computed tomography (µ-CT) projections demonstrate that increasing iodine

content results in greater X-ray contrast. Compression tests of dry and wet porous scaffolds

indicate that the poly(1-IPHE-6)0.24-co-poly(1-PHE-6)0.76 material results in the highest

compression modulus. MC3T3 cell viability and spreading studies show PEUs are non-toxic to

cells. As most medical device procedures require placement verification via fluoroscopic

imaging, materials that possess inherent X-ray contrast are valuable for a number of

applications.

11



Structure – Property Relationships of ‘Peptide-like’ Polyesters

Qianhui Liu, Ying Xu, Abraham Joy

Polyesters properties such as thermal stability, mechanical strength, hydrophilicity,

degradation rate and crystallinity are critical aspects for polyesters used in various

applications. Changing molecular structure is a way to modulate materials

properties.

We have previously reported the design of polyesters with ‘peptide-like’ pendant

functional groups by room temperature polymerization of pendant functionalized

diols and diacid[1]. On this basis, we further examined the relationship between the

chemical structures and properties by changing pendant functional groups of the

diols and diacids. In this work, functional groups such as alkyl group, phenyl group,

hydroxyl group and carboxyl group were introduced into the side chain, meanwhile,

succinic acid and sebacic acid were selected as the diacids. All polymer structures

were determined by NMR and IR. Characterization such as glass transition

temperature, decomposition temperature, shear modulus, water contact angle,

hydrolytic degradation and viscosity were carried out. The data detail how properties

change with different structures. Increasing diacid chain length leads to flexible

polymer chains followed by lower glass transition temperature, and slower hydrolytic

degradation rate. Introduction of phenyl groups increases stiffness of polymer

resulting to higher glass transition temperature, and higher hydrophobicity as well as

lower degradation rate. While, Introduction of carboxyl group and hydroxyl group

leads to increased hydrophilicity and faster degradation rate. Overall the work

provides a platform for understanding the structure-property relationships of

pendant functionalized polyesters.

References:

[1]. S. Gokhale, Y. Xu, Biomacromolecules, 2013, 14 (8), pp 2489–2493

12



Synthesis of Well-Defined Poly(propylene fumarate) Oligomers and Their Use in 3D Printed Scaffolds via Continuous Digital Light Processing

Three-dimensional (3D) printed biodegradable polymer scaffolds are attractive candidates for bone tissue engineering due to their high mechanical strength and the controlled pore properties (porosity, pore size) of the scaffolds for bone in-growth from the nature of 3D printing. PPF oligomers exhibit low viscosity at room temperature and have double bonds in the backbone chains which make them useful for UV curable 3D printing resin. A ring opening polymerization method for synthesizing PPF oligomers provides a rapid, and scalable technique of synthesizing PPF with well-defined molecular mass, controlled molecular mass distribution (Đm), and suitable viscosity properties for 3D printing. These properties will also reduce the amount of solvent necessary to ensure sufficient flow of material during 3D printing. MALDI mass spectrometry precisely shows the end group fidelity, and size exclusion chromatography (SEC) demonstrates narrow mass distributions (<1.6) of a series of low molecular mass oligomers (700−3000 Da). The corresponding intrinsic viscosities range from 0.0288 ± 0.0009 dL/g to 0.0780 ± 0.0022 dL/g. The oligomers were printed into scaffolds via established photochemical methods and standardized ISO 10993-5 testing showed that the 3D printed materials are nontoxic to both L929 mouse fibroblasts and human mesenchymal stem cells.

Author : YuanYuan Luo

13






Peptide-dendrimer Conjugates for Implant Functionalization

Derek Luong, Chad Broering, Mary Beth Wade, Eric Miller, Matthew L. Becker

ABSTRACT

Titanium continues to be the gold standard material for orthopedic applications as a consequence of its durability under physiological conditions and non-immunogenic properties. However, patients with metabolic diseases such as diabetes suffer from a lack of osseointegration with the implant, resulting in undesired side effects such as inflammation and aseptic loosening.1-2 This results in revisional surgery, causing physical and emotional distress to the patient. Recent research has shown that modifying titanium surfaces with synthetic bioactive molecules mimicking natural proteins increases osseointegration.3 A modular molecule was synthesized with a bioactive domain consisting of a peptide and a titanium-binding domain consisting of a catechol-based dendron. Mouse calverial derived stem cells (MC3T3) seeded on titanium functionalized with this modular molecule showed up-regulation of osteogenic markers bone sialoprotein (BSP) and osteocalcin (OCN) by 3-fold and 60-fold respectively relative to controls after 21 days. In addition, there was a 3-fold increase in calcium deposition.4 In this research, a study was performed in vivo by coating titanium (Ti6Al4V) pins with the modular molecule and implanting them into Sprague Dawley Rat femurs. Four different modular molecules were synthesized and tested, each possessing the same binding domain but a different peptide domain. The four peptides chosen are short peptide mimics of osteogenic growth peptide (OGP), and three different bone morphogenetic proteins (BMP): BMP-2, BMP-7, and BMP-9. Each coating will be evaluated using a pull-out biomechanics test and histology to assess the ability for these bioactive molecules to increase osseointegration. References:

1) Chan, P.; Brenkel, I.; Aderinto, J. Current Orthopaedics 2005, 19, 59-67. 2) Yang, Z.; Liu, H.; Xie, X.; Tan, Z.; Qin, T.; Kang, P. The Bone & Joint Journal

2014, 96-B, 1637-1643.. 3) Reyes, C.; Petrie, T.; Burns, K.; Schwartz, Z.; García, A. Biomaterials 2007, 28,

3228-3235. 4) Tang, W.; Policastro, G.; Hua, G.; Guo, K.; Zhou, J.; Wesdemiotis, C.; Doll, G.;

Becker, M. J. Am. Chem. Soc. 2014, 136, 16357-16367.

14



Polyphosphazenes as nitric oxide release platforms Alec Lutzkea, Bella H. Neufelda, Megan J. Neufelda, and Melissa. M. Reynoldsabc

aDepartment of Chemistry, bSchool of Biomedical Engineering, and cDepartment of Chemical & Biological Engineering, Colorado State University, Fort Collins, CO 80523, USA.

Nitric oxide (NO) is an endogenous molecule that participates in multiple physiological processes, including the immune response and regulation of vasodilation. As a critical component of normal endothelial function, NO has been delivered from various blood-contacting polymeric materials to improve their biological compatibility. Furthermore, exogenous NO has been established to function as an effective antithrombotic and antimicrobial agent, in addition to exerting wound-healing effects at the site of an injury. We have explored the ability of the cysteine-based polyphosphazene poly(ethyl S-methylthiocysteinyl-co-ethyl cysteinyl phosphazene) to function as a platform for NO release under physiological conditions, and performed preliminary cell compatibility studies using human dermal fibroblasts (HDF). Our work suggests that NO-releasing polyphosphazenes may serve as useful biomaterials with high relative NO loading (0.55 ± 0.04 mmol g-1) and the ability to serve as short-term reservoirs of releasable NO.

15



Bioinspired Antimicrobial Polyurethanes: A New Tool for Combating Bacterial Infections Steven Mankoci1, Rick Kaiser1, Hazel Barton2, Nita Sahai1, and Abraham Joy1*

1University of Akron, Department of Polymer Science, Akron, OH 44325-3909 2University of Akron, Department of Biology, Akron, OH 44325-3908

The development of drug resistant strains of bacteria is a serious threat to the well being of everyone worldwide. A promising approach to addressing this problem is the development of synthetic polymers which mimic naturally occurring antimicrobial peptides. We will describe the development of synthetic peptide-like polyurethanes from amino acid-like diol monomers, tailored for anti-microbial activity. This study details the application of these peptide-like polymers to create materials which resemble and function similarly to antimicrobial peptides. The ability of these polymers to prevent growth and kill gram negative and gram positive bacteria will be presented, along with their compatibility with mammalian cells.

16



Development of antimicrobial fibers using biologically-derived peptide-nucleic

acids (PNAs): Attachment, efficacy and release

Ryan J. Mondschein1, Allison M. Pekkanen2, Denis Guenette3, Nrusingh Mohapatra3, Timothy E.

Long1

1Department of Chemistry & Macromolecules and Interfaces Institute (MII)

2Department of Biomedical Engineering and Mechanics (BEAM)

Virginia Tech., Blacksburg VA 24061 3Techulon Inc., Blacksburg, VA 24060

Email: [email protected]

Methicillin-resistant staphylococcus aureus (MRSA) continues to plague patients with severe skin

infections that are resistant to a number of antibiotics, both in and out of hospital settings. In

particular, military personnel are often exposed to this deadly bacteria with little to no medial support

to fight the disease. To help prevent infection, peptide nucleic

acids (PNAs) have been developed that are specific to MRSA;

these PNAs could selectively destroy bacteria present on the

skin of military personnel through release from an anti-

bacterial shirt. This study aims to characterize the adhesion of

PNAs, and peptides in general, to nylon, cotton, and 50/50

nylon/cotton blended fabrics. Due to the high production

expense of PNAs, a model peptide (shown in Figure 1) was

developed to both limit costs and provide molecular beacons

for analysis. The sulfur atom present can be detected with

elemental analysis (XPS, EDS) and the phenylalanines provide

a strong UV-Vis peak around 230 nm. Analysis with SEM

visually confirmed the peptide’s presence on fiber surfaces

(Figure 1), regardless of fiber drying time or method.

Furthermore, repeated rinse cycles of the fabrics showed the

peptide remained on the surface of the fibers despite the

presence of water and agitation. The model peptide showed a

strong correlation on UV-Vis between concentration and

absorbance, and the calibration curve from this analysis was

used to determine the concentration of released peptide from

fiber surfaces. PNA-coated fabrics show a similar morphology

under SEM, indicating that the model peptide is a strong

predictor of the behavior of the PNA. Future studies to

investigate the mechanism of peptide adhesion to fiber surfaces

as well as evaluate differences between nylon and cotton are currently under investigation.

Acknowledgements: This work was funded by Techulon Inc. through a U.S. Army STTR.

Figure 1. (top) Structure of

designed model peptide.

(bottom) SEM image

showing model peptide-

coated fibers

17



Solvent-Free, Photocurable Mussel-Inspired Polyester Adhesive for Underwater Adhesion

Amal Narayanan, Qianhui Liu, Ying Xu, Abraham Joy

Department of Polymer Science, The University of Akron, Akron, Ohio 44325, United States

Mytilus edulis (mussels) is known for its ability to adhere to hydrophilic surfaces under water. The

adhesion and cohesion are brought about by the post-translationally modified peptides, such as L-3,4-

dihydroxy phenylalanine (DOPA) and phosphoryl serine. Inspired by mussel adhesion, we have developed

a solvent-free underwater polyester adhesive. The adhesive was designed to flow at room temperature such

that it can be dispensed without the addition of any solvent. This was achieved by the design of a monomer

with amide substituted hydrophobic aliphatic chains derived from soybean oil. The aliphatic chains also

provide a hydrophobic environment which can displace water from the substrate. A second diol was

designed with DOPA units to provide adhesive interactions with the substrate. A third diol with coumarin

pendant groups provided temporal control of polymer chain-crosslinking, leading to an increase of cohesive

interactions in the adhesive.

In lap-shear strength measurements, 20.0 mg of polymer spread onto oxidized glass slides and

exposed to 5 min UV irradiation ( > 350 nm, power on substrate = 0.5 W/cm2) on a lap-joint (area = 6.45

cm2) displayed lap-shear strength of 0.9 MPa. Immersion of the lap-joint underwater for 24 h did not

decrease the lap-shear strength of the adhesive. Additionally, the lapshear strength of polymer when applied

underwater on lap-joints of glass and various substrates (aluminum, stainless steel, polyethylene,

poly(methylmethacrylate), porcine skin) showed conclusively that the above adhesive could be used as

underwater adhesives on various substrates.

18



Title: Antimicrobial IPN naofiber scaffolds for applications of wound healing Authors: Sepideh Niknezhad, Sadhan C Jana The main purpose of this study was to investigate the antimicrobial properties of the IPN polymeric matrix prepared by Gas-Jet spinning technology (GJS) and core-shell nozzle configuration. The biocompatible polyvinyl pyrrolidone (PVP) was fed into the core and the biocompatible polyvinyl acetate (PVAc) was processed as shell. Tetracycline hydrochloride was chosen as a model drug in this study and placed in three different locations of core, shell, and both core and shell. The surface morphology and smoothness of nanaofibers were studied by Scanning Electron Microscopy (SEM). The release rate of the scaffolds were investigated and Staphylococcus Epidermidis and Pseudomonas aeruginosa (PAO1) were two Gram-positive and Gram-negative strains that were processed in antimicrobial assessment. The scaffolds showed very promising antimicrobial properties against these two strains and are good candidates for wound dressing materials.

19



Injectable and Thermosensitive Hydrogels with High Oxygen Permeability

Hong Niu, Zhaobo Fan, Jianjun Guan

Department of Materials Science and Engineering, The Ohio State University

Stem cell therapy is promising for ischemic tissue regeneration. Using hydrogels with high

oxygen permeability as cell carriers may improve cell survival under ischemic conditions. We

have developed a family of injectable and thermosensitive hydrogels with high oxygen

permeability. The hydrogels were synthesized by reversible addition-fragmentation chain

transfer (RAFT) polymerization of N-isopropylacrylamide (NIPAAm), acrylate polylactide (APLA),

and 2-Hydroxyethyl methacrylate (HEMA), and poly(ethylene glycol) conjugated with

perfluorooctane (PEGPFC). 1H-NMR spectra demonstrated that the hydrogel compositions were

consistent with feed ratios. The hydrogels exhibited sol-gel temperatures around room

temperature. The hydrogel solutions were flowable at 4oC and can be readily injected through a

26G needle typically used for tissue injection. When transferred to a 37oC water bath, the

solutions quickly solidified (within 4 s) and formed highly flexible gels. The hydrogels were

degradable with <25% weight loss when incubated in PBS for 4 weeks. To characterize hydrogel

oxygen permeability, electron paramagnetic resonance (EPR) was used to measure oxygen

partial pressure in the hydrogel. The results demonstrated that the hydrogels had oxygen

permeability similar to that of the PBS. These hydrogels show attractive properties for use as

cell carriers.

20



Non-viral Gene Delivery Utilizing Imidazolium-containing Polyesters

Allison M. Pekkanen1, Ashley M. Nelson

2, Ryan J. Mondschein

2, Timothy E. Long

1,2

1School of Biomedical Engineering and Sciences, Virginia Tech, Blacksburg, VA 24061

2Department of Chemistry, Macromolecules Innovation Institute, Virginia Tech, Blacksburg, VA

24061

Gene delivery is a promising therapeutic option for the treatment of a wide variety of diseases

involving mutated or missing genes. As the genetics of disease becomes better understood,

therapeutic options to treat these diseases must also be improved. The most common non-viral

gene delivery vehicles are positively charged polymers, dendrimers, and micelles, but many are

plagued with cytotoxicity due to the high concentration of positive charge. In this work, a novel

imidazolium diol is synthesized and utilized to create a series of polyesters of varying charge

content and varying charge density. Initial studies utilize the imidazolium diol along with

neopentyl glycol to evaluate the effect of wt % charge on the DNA binding, cytotoxicity, and

transfection efficacy. Melt polycondensation was accomplished with a temperature ramp of 150

°C for 12 h, 200 °C for 12 h, and 200 °C plus 0.2 mbar vacuum for 6 h to remove condensate.

These resulting polyesters exhibit a Tg range of 80 °C, indicating the ability to tune polymer

properties by changing the amount of charge. Additionally, these polyesters indicate a high

degree of association between the DNA and polyesters which is exhibited by a low

hydrodynamic diameter and colloidal stability over time. Furthermore, the effect of charge

density of polyesters was investigated for 50 mol % imidazolium diol with a series of codiols of

diethylene glycol, tetraethylene glycol, poly(ethylene glycol) (PEG) 400, and PEG 1000. The

synthesis of this series of polyesters proceeds as observed with neopentyl glycol, but with the

additional benefits afforded from the addition of colloidal stability afforded from the PEG. These

polyesters have the ability to improve dramatically on the gold standard gene delivery vectors

through their enhanced colloidal stability and their lack of cytotoxicity.

Figure 1. DSC of imidazolium polyesters reveals a Tg range of 80 °C, with those compositions

above 30 wt % imidazolium diol exhibiting water dispersibility.

-50

-40

-30

-20

-10

0

10

20

30

40

50

0 20 40 60 80 100

Tg

(°C

)

Wt. % Imidazolium Diol Charged

Tg, experimental

Fox Equation Prediction

Water Dispersible

21



Enzyme-Promoted H2S Releasing Polymers

Chad R. Powell, Kyle J. Arrington, Jeffrey C. Foster, Benjamin Okyere, Michelle Theus, John B.

Matson

We report the synthesis of an H2S releasing, polymer based on a small molecule that presents a

novel method of releasing hydrogen sulfide (H2S) through in situ enzymatic conversion. Water

soluble copolymers were prepared resulting in innocuous byproducts upon H2S delivery. Both

the polymer and small molecule H2S donors have release half-lives on the order of hours in the

presence of a ubiquitous enzyme in buffered aqueous media. Additionally, both the monomer

and polymer show limited cytoxocity and induce proliferation of endothelial cells, in line with

delivery of existing H2S donors.

22



Abstract for Poster in Akron Summer 2016

“Controlled Release of a Peptide Drug from PLGA Nanospheres”

Rose Robertsa, Samy Lamouilleb,c, Robert Gourdieb,d,e,f, Johan Fostera

aVirginia Tech, Macromolecule Innovation Institute, Materials Science and Engineering

Department, Blacksburg, Virginia bVirginia Tech Carilion Research Institute, Center for Heart and Regenerative Medicine

Research, Roanoke, Virginia cFirst-String Research Inc., Mount Pleasant, South Carolina. dFaculty of Health Science, Virginia Tech, Blacksburg, Virginia. eVirginia Tech-Wake Forest University School of Biomedical Engineering and Sciences, Blacks-

burg, Virginia. fDepartment of Emergency Medicine, Virginia Tech Carilion School of Medicine, Roanoke,

Virginia

Chronic wounds, such as diabetic foot ulcers, occur more as patients increase in age and weight,

and the additional health issues that come with them.1 Diabetic foot ulcers (DFUs) affect about

15% of those with diabetes, and 84% of diabetic amputations of the lower leg are preceded by

DFUs. While wound healing is a complex process, one overarching factor causing chronic wounds

is prolonged inflammation.2 A new drug called ACT1 (Alpha Connexin carboxy Terminus 1) is a

synthetic peptide that has been shown to decrease inflammation and promote wound healing in

clinical trials with patients having diabetic foot ulcers and other chronic wounds.3,4 However, as

ACT1 is a short molecule, it has a short half-life in the body.5 We present the controlled release of

ACT1 from polymer nanospheres, designed to prolong the presence of the drug in the body, while

reducing reapplication. Particle size was optimized for ability to sterilize by filtration. Degradation

was studied over the course of three weeks in phosphate buffered saline solution at 37 °C.

23



References

1. Werdin, F., Tennenhaus, M., Schaller, H.E., Rennekampff, H.O. “Evidence-based

Management Strategies for Treatment of Chronic Wounds.” ePlasty 2009 9:169-179.

2. Guo, S., DiPietro, L.A. “Factors Affecting Wounds Healing.” Journal of Dental Research

2010 89(3):219-229.

3. Grek, C.L., Prasad, G.M., Viswanathan, V., Armstrong, D.G., Gourdie, R.G., Ghatnekar,

G.S. “Topical administration of a connexin43-based peptide augments healing of chronic

neuropathic diabetic foot ulcers: A multicenter, randomized trial.” Wound Repair and

Regeneration 2015 23:203-212.

4. Ghatnekar, G.S., Grek, C.L., Armstrong, D.G., Desai, S.C., Gourdie, R.G. “The effect of

a Connexin43-based peptide on the healing of chronic venous leg ulcers: A multicenter,

randomized trial.” Journal of Investigative Dermatology 2015 135: 289-298.

5. Grek, C.L., Rhett, J.M., Ghatnekar, G.S. “Cardiac to cancer: Connecting connexins to

clinical opportunity.” FEBS Letters 2014 588:1349-1364.

24



Recyclable Green Chemistry Catalysts Based on Directed Self-Assembly of Amphiphilic Block

Copolymers

Dieter Scheibel, Ivan Gitsov Michael M. Szwarc Polymer Research Institute & Department of Chemistry State University of New York ESF Syracuse, NY 13210

This study focuses on the modification and immobilization of the glycoprotein laccase via non-covalent binding. Block ABA copolymers composed of poly(ethylene glycol) as the central B block and either Frechet’s dendrons, hyperbranched poly(p-chloromethylstyrene), or linear poly(styrene) as the A segments were synthesized and used as physically immobilizing agents. By controlling the hydrophilic-hydrophobic weight ratio of the immobilizing agents, micelles and hydrogel networks capable of reusability were obtained.

Laccase modified with all amphiphilic copolymers displayed an increase in activity towards ABTS when compared with the native enzyme. Activity increases between 4% and 420% were observed, with linear-linear-linear copolymers causing the greatest increase in activity. It was observed that the size of the PEG spacer in hydrogels plays a significant role in enzyme activity, with longer PEG spacers causing a significant increase in activity in contrast to shorter PEG spacers. Activity changes can be attributed to conformational changes and differences in mobility of the enzyme when modified or immobilized in micellar and hydrogel networks respectively. Hydrogel density, determined by length of the PEG spacer, was also found to influence substrate diffusion to the enzyme.

Laccase activity towards hydrophobic substrates increased noticeably when immobilized in all block copolymers. This increase can be attributed to the hydrophobic substrates being preferentially sequestered in the hydrophobic domains created by the copolymers in proximity to the enzyme active site. Enzyme reusability was demonstrated with hydrogel complexes where laccase, immobilizing copolymer, and unreacted monomer can be recycled. Decolorization of synthetic dyes by native and complexed laccase was also examined as proof of principle. Although rate of decolorization was greatest with native laccase, the reusability afforded by immobilized laccase makes the latter a more practical option for such water treatment purposes. Future studies include investigating the aforementioned laccase complexes in additional catalytic roles, such as small molecule organic synthesis.

25



Functionalized nanofiber scaffolds for nerve regeneration

Elena Silantyeva†, Jacqueline Carpenter‡, Rebecca K. Willits‡, Matthew L. Becker†

The University of Akron Department of Polymer Science†, Department of Biomedical Engineering‡

Akron, Ohio, 44304

Abstract

Peripheral nerve injuries are a significant clinical challenge due to the limited capacity of nerve tissue to regenerate.1 Differentiation of embryonic stem cells (ESCs) in vitro can provide a novel source of cells for neural tissue replacement or repair.1 In order to advance the use of ESCs for clinical practice there is a need to overcome limitations such as: 1) a lack of well-defined, xeno-free culture systems for directed differentiation of ESCs; 2) a lack of systematic control over culture conditions that regulate ESC behavior; 3) inability to produce neurons from ESCs on large scale.2 The Becker Lab has developed a synthetic nanofiber substrate that has demonstrated effective differentiation of mouse ESCs to neural progenitors within one day.3 It is established that multiple bioactive molecules work synergistically to regulate cell function, but there are very few reports describing substrates with more than one attached bioactive group.4 We have reported scaffolds that can be functionalized with two peptides or carbohydrates.4 This research seeks to overcome the limitations mentioned above through the creation of polymer nanofibers functionalized with three peptide sequences (GRGDS, GYIGSR and FGL) for directed differentiation of ESCs into neural lineage and development of mature neural cells. Poly(ε-caprolactone-co-2-oxepane-1,5-dione) functionalized with 4-dibenzocyclooctynol was successfully synthesized and used for creation of random and aligned nanofibers using electrospinning. Surface functionalization of nanofiber scaffolds with three peptides was performed using strain promoted alkyne-azide cycloaddition, oxime ligation and thiol-ene “click” chemistry. Study on differentiation of mouse ESCs to neural lineage is ongoing. The developed substrates can be extended for controlled differentiation and maturity of other lineages.

References:

1) Daly, W. et al. J. R. Soc. Interface 2012, 9, 202-221.

2) Brafman, D.A. et al. Biomaterials 2010, 31 (34), 9135-44.

3) Callahan, L.A. et al. Biomaterials 2013, 34 (36), 9089-95.

4) Zheng, J. et al. Biomacromolecules 2015, 16, 357-563.

26



Development of Solvent Spinning Process for Bacterial Polyester Bhavya Singhi1, Radhika Vaid1, Dr. Martin King1

1 College of Textiles, North Carolina State University, Raleigh, NC - 27606

ABSTRACT

Polyhydroxyalkanoates (PHAs), also known as bacterial polyester, have emerged as an attractive

biomaterial in the last decade due to its biodegradability. A wide range of hydroxyalkanoate

units with varying mechanical and structural properties can be harvested through bacterial

synthesis. Owing to the versatility of PHAs, their biocompatibility and resorbability have

resulted in extensive use in biomedical applications such as sutures and wound dressings. They

have also been explored for controlled release applications involving a variety of chemicals and

drugs, some of which are thermally sensitive. Commercially, PHAs are processed via melt

spinning at temperatures as high as 200 °C. Extruded filaments exhibit a high degree of

polymerization with high molecular weights. But due to the high melt spinning temperatures, the

combination with thermally sensitive drugs means that they need to be incorporated in a post

spinning process. This raises the need for a low temperature wet spinning or gel spinning

process for bacterial polyester that will address the major drawbacks associated with

incorporating drugs post melt spinning, such as non-uniform absorption and an uneven release

profile. In order to accomplish this we have studied the chemical properties of PHA so as to

develop a low temperature solvent spinning process. Multiple solvents, such as methylene

dichloride, tetrahydrofuran, dioxane and chloroform have been evaluated for dissolution of poly

(3-hydroxybutyrate-4-hydroxybutyrate) (P34HB). This preliminary solvent study has enabled us

to identify methylene dichloride as the most suitable solvent. Currently we are determining the

optimal coagulation conditions for polymer regeneration in methanol as well as the drawing

conditions required to produce a strong and oriented filament. This study will facilitate the

development of a single step process for drug incorporation during PHA fiber spinning, which

can be utilized in a range of different medical and healthcare products.

Key words: Polyhydroxyalkanoates, solvent spinning, methylene dichloride

27



A comparative study on the in vitro and in vivo properties of

sequenced controlled and random poly(lactic-co-glycolic acid)s

Michael A. Washington †, Morgan V. Fedorchak ‡§⊥, Steven R. Little ‡∥ ¶ ⊥, Simon C. Watkins *#,

Tara Y. Meyer †⊥

†Department of Chemistry, ‡Chemical and Petroleum Engineering, §Ophthalmology, ∥Bioengineering, ¶Immunology, *Cell Biology and Physiology, #Centers for Biological Imaging,

University of Pittsburgh, Pittsburgh, PA 15261, ⊥McGowan Institute for Regenerative Medicine,

University of Pittsburgh, Pittsburgh, PA 15261

Poly(lactic-co-glycolic acid) (PLGA)-based biodegradable materials have attracted

considerable interest in the field of bioengineering due to its biocompatibility, FDA approval and

tunable physico-chemical properties. However, the current methods for tuning the properties of

PLGAs for a specific therapeutic application are limited to changing the monomeric ratio and

stereochemistry of cyclic esters prior to ring-opening polymerization (ROP), resulting in an

unsequenced, random copolymer. This study focuses on evaluating the properties of a new set of

precisely sequenced PLGAs prepared via segmer assembly polymerization (SAP). PLGAs

synthesized by SAP contain exact repeating sequences whose components are interchangeable,

which allows for a directed synthesis of sequences tailored for a specific application. Changes in

sequence, stereochemistry and monomeric ratios were shown to have a profound effect on such

properties as in vitro erosion, swelling, acidic microclimate distribution and compressive modulus.

Devices fabricated with sequenced PLGAs were shown to have enhanced stability both in vitro

and in vivo. These results emphasize the importance of using monomeric sequence to control the

hydrolysis kinetics of a copolymer which contains a variety of hydrolyzable linkages.

28






N-carboxyanhydrides for bone growth repair

James Wilson1, Matthew Becker1

1Department of Polymer Science, The University of Akron

Abstract

The ring-opening terpolymerisation of the N-carboxyanhydrides (NCAs) alanine-NCA,

tyrosine-NCA and phenylalanine-NCA has been investigated as an alternative to poly(1-

PHE-6) polyester ureas for use in bone growth repair. Whilst modified poly(1-PHE-6)

has been demonstrated to assist in bone growth repair, degradation by-products contain

carboxylic acid groups known to cause inflammation on the surrounding tissue. Hence,

the use of a controlled molecular weight polypeptide material analogous to poly(1-PHE-

6) is studied in order to avoid inflammation as well as optimise mechanical properties.

The use of functionalised NCAs for post-polymerisation modification is also investigated

as a means to incorporate bone growth peptides on the active surface of the implant.

29



THE UNIVERSITY OF AKRON

Department of Polymer Science

12th

National Graduate Research Polymer Conference

June 19-22, 2016

Goodyear Polymer Center

Contact-Killing Antimicrobial Thermoplastic Polyurethanes for Catheter Applications

Zachary K. Zander, Yaohua Gao, Joe Conti, Alec Cerchiari, Matthew L. Becker

ABSTRACT

Catheter-related blood stream infections (CRBSIs) and

catheter-associated urinary tract infections (CA-UTIs) occur

quite frequently; in the ICU alone, ~80,000 CRBSIs are

reported annually, resulting in 28,000 deaths per year.1

This

problem contributes a $2.3 billion annual burden to the U.S.

healthcare system as a result of further treatment costs and

extended hospital stays.1 Additionally, UTIs account for 30-

40% of all hospital-acquired infections world-wide, and

roughly 80% of these are catheter-associated.2 Antibiotics are

often employed to treat patients with cather-associated

infections (CAIs), however, excessive use of antibiotics has

produced bacterial resistance at an alarming rate. Thus, there

is a need for sterile surface materials that do not employ

antibiotics for reducing bacterial growth and infections.3,4

Herein, we describe a thermoplastic polyurethane (TPU)

system with tethered quaternary ammonium compounds

(QACs) for efficient contact-killing of both gram negative and gram positive bacteria. QACs

have been widely utilized in household disenfectant products. Even though the mechanism of

action for their contact-killing properties remains somewhat elusive, literature accounts seems

to agree that they are membrane-active agents which physically disrupt the bacterial cell wall.5

In this research, the QACs are covalently attached to TPU by surface grafting or functional

monomer methods, and the efficacy of both are evaluated for catheter applications. Eventually,

a series of QACs consisting of various spacer lengths and chain lengths will be analyzed for

optimal antimicrobial activity.

References 1. APIC, Guide to the Elimination of Catheter-Bloodstream Infections (2009). http://www.apic.org/

2. Donelli, G.; et al. In Biofilm-Based Healthcare-Associated Infections; Donelli, G., Ed.; Springer International

Publishing; 2015; Vol. 831, p. 93.

3. Siddenbiedel, F.; Tiller, J.C. Polymers 2012, 4, 46.

4. Otto, M. Nat. Rev. Micro 2009, 7, 555.

5. Denyer, S.P; Hanlon, G.W.; Ioannou, J.C. Antimicrobial Agents and Chemotherapy 2007, 51 (1), 296

30

http://www.apic.org/



Dendritic Elastin-like Peptides: The Effect of Branching on

Thermoresponsiveness

Mingjun Zhou

Advisor: John Matson

Virginia Tech.

Elastin-like peptides (ELPs) have been used widely to confer thermoresponsive

characteristics onto various materials, but to this point mostly linear ELPs have been

studied. A class of linear and dendritic (branched) ELPs based on the GLPGL pentamer

repeat unit was synthesized using an on-resin divergent strategy. The effect of peptide

topology on the transition temperature (Tt) was examined using circular dichroism to

study the peptide secondary structure transition and turbidity to measure the macroscopic

phase transition (coacervation). Secondary structure transitions showed no dependence on

topology, but a higher Tt was observed for dendritic peptides than for linear peptides with

the same number of GLPGL repeats. The data support a phase transition model that

consists of two neighboring processes: a secondary structure transition, related to

intramolecular interactions, followed by coacervation, associated with intermolecular

interactions.

31



UV-nanoimprint lithography as a tool to develop flexible microfluidic devices for electrochemical

detection

Yiliang Zhou, Juhong Chen, Sam R. Nugen, Kenneth R. Carter and James J. Watkins

University of Massachusetts, Amherst, USA

Research in microfluidic biosensors has led to dramatic improvements in sensitivities. Very few

examples of these devices have been commercially successful, keeping this methodology out of

the hands of potential users. In this study, we developed a method to fabricate a flexible

microfluidic device containing electrowetting valves and electrochemical transduction. The

device was fabricated by UV-nanoimprint lithography and designed to be amenable to a roll-to-

roll manufacturing system, allowing a low manufacturing cost. Actuation of the multivalve

system with food dye in PBS buffer was performed to demonstrate automated fluid delivery.

The device was then used to detect Salmonella in a liquid sample.

32

Documents

Poster Presentations: Biomaterials - The University … Presentations: Biomaterials. 12. th. National Graduate Research Polymer Conference 2016 | College of Polymer Science and Polymer