Publications (63) View all
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Article: Recombinant Reflectin-Based Optical Materials
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ABSTRACT: Reflectins are a unique group of structural proteins involved in dynamic optical systems in cephalopods that mod-ulate incident light or bioluminescence. We describe cloning, structural characterization, and optical properties of a reflectin-based domain, refCBA, from reflectin 1a of Hawaiian bobtail squid, Euprymna scolopes. Thin films created from the recombinant protein refCBA display interesting optical features when the recombinant protein is appropriately organized. RefCBA was cloned and expressed as a soluble protein ena-bling purification, with little structural organization found using Fourier transform infrared spectroscopy and circular dichroism. Single-layer and multi-layer thin films of refCBA were then pro-duced by flow coating and spin coating, and displayed colors due to thin film interference. Diffraction experiments showed the assemblies were ordered enough to work as diffraction gratings to generate diffraction patterns. Nano-spheres and la-mellar microstructures of refCBA samples were observed by scanning electron microscopy and atomic force microscopy. Despite the reduced complexity of the refCBA protein com-pared to natural reflectins, unique biomaterials with similar properties to reflectins were generated by self-assembled reflectin-based refCBA molecules. V C 2012 Wiley Periodicals, Inc.Journal of Polymer Science Part B Polymer Physics 01/2013; 51:254-264. · 1.53 Impact Factor -
Article: Salt-Leached Silk Scaffolds with Tunable Mechanical Properties.
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ABSTRACT: Substrate mechanical properties have remarkable influences on cell behavior and tissue regeneration. Although salt-leached silk scaffolds have been used in tissue engineering, applications in softer tissue regeneration can be encumbered with excessive stiffness. In the present study, silk-bound water interactions were regulated by controlling processing to allow the preparation of salt-leached porous scaffolds with tunable mechanical properties. Increasing silk-bound water interactions resulted in reduced silk II (β-sheet crystal) formation during salt-leaching, which resulted in a modulus decrease in the scaffolds. The microstructures as well as degradation behavior were also changed, implying that this water control and salt-leaching approach can be used to achieve tunable mechanical properties. Considering the utility of silk in various fields of biomedicine, the results point to a new approach to generate silk scaffolds with controllable properties to better mimic soft tissues by combining scaffold preparation methods and silk self-assembly in aqueous solutions.Biomacromolecules 09/2012; · 5.48 Impact Factor -
Article: Mechanism of resilin elasticity.
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ABSTRACT: Resilin is critical in the flight and jumping systems of insects as a polymeric rubber-like protein with outstanding elasticity. However, insight into the underlying molecular mechanisms responsible for resilin elasticity remains undefined. Here we report the structure and function of resilin from Drosophila CG15920. A reversible beta-turn transition was identified in the peptide encoded by exon III and for full-length resilin during energy input and release, features that correlate to the rapid deformation of resilin during functions in vivo. Micellar structures and nanoporous patterns formed after beta-turn structures were present via changes in either the thermal or the mechanical inputs. A model is proposed to explain the super elasticity and energy conversion mechanisms of resilin, providing important insight into structure-function relationships for this protein. Furthermore, this model offers a view of elastomeric proteins in general where beta-turn-related structures serve as fundamental units of the structure and elasticity.Nature Communications 08/2012; 3:1003. · 7.40 Impact Factor -
Article: Stabilization of vaccines and antibiotics in silk and eliminating the cold chain.
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ABSTRACT: Sensitive biological compounds, such as vaccines and antibiotics, traditionally require a time-dependent "cold chain" to maximize therapeutic activity. This flawed process results in billions of dollars worth of viable drug loss during shipping and storage, and severely limits distribution to developing nations with limited infrastructure. To address these major limitations, we demonstrate self-standing silk protein biomaterial matrices capable of stabilizing labile vaccines and antibiotics, even at temperatures up to 60 °C over more than 6 months. Initial insight into the mechanistic basis for these findings is provided. Importantly, these findings suggest a transformative approach to the cold chain to revolutionize the way many labile therapeutic drugs are stored and utilized throughout the world.Proceedings of the National Academy of Sciences 07/2012; 109(30):11981-6. · 9.68 Impact Factor -
Article: Protein-based composite materials
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ABSTRACT: Natural structural proteins display critical structural and bioactive properties that have evolved in nature for millions of years. However, depending on the specific protein, there may be useful functions, such as mechanical toughness, while other critical features may be more limiting, such as cell compatibility or a broader range of mechanical properties. Nature has evolved strategies to resolve this problem by generating multifunctional composite materials in vivo. For example, collagen and elastin are often found together in the body to provide the combination of strength and toughness required for specific tissue functions 1 . Blending (mixing) proteins is a technological approach to generate protein-based biomaterials with a more complete set of specific properties. Blending can also benefit materials engineering through improved processability and material uniformity. As an alternative to blending, genetic engineering strategies have been exploited to generate combinations or hybrids of structural proteins to achieve control of functional features. However, at present this process remains limited due to the costs of scale up for these biotechnologically driven processes. Therefore, generating multifunctional, biodegradable structural protein composite biomaterials is emerging as a useful direction in the field to tailor properties to specific medical needs in vitro and in vivo, or as a strategy to generate a broader range of functional properties with which to conduct more systematic studies of the impact of the biomaterials on cell and tissue functions. Natural structural proteins Many natural proteins have been studied, with distinguishing mechanical, chemical, electrical, electromagnetic, and optical properties. Elastins, collagens, silks, keratins, and resilins are some of the more common structural proteins considered for protein-based biomaterials (Fig. 1). In Protein-based composite biomaterials have been actively pursued as they can encompass a range of physical properties to accommodate a broader spectrum of functional requirements, such as elasticity to support diverse tissues. By optimizing molecular interfaces between structural proteins, useful composite materials can be fabricated as films, gels, particles, and fibers, as well as for electrical and optical devices. Such systems provide analogies to more traditional synthetic polymers yet with expanded utility due to the material's tunability, mechanical properties, degradability, biocompatibility, and functionalization, such as for drug delivery, biosensors, and tissue regeneration.Materials Today 05/2012; 15(5):208-215. · 5.57 Impact Factor
