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ABSTRACT: Wound healing is a complex, multistep process that can be summarized into three stages, namely, hemostasis and inflammation, proliferation, and finally, tissue remodeling. Battlefield wound healing demands rapid hemostasis using clotting or cauterizing agents to immediately limit blood loss, but this occurs at the expense of proper tissue repair beyond hemostasis. Layered silicate clays such as kaolin and montmorillonite (MMT) have been previously shown to induce blood clotting due to their ability to form charged interactions with clotting factors. The charge characteristics of sodium MMT (Na-MMT) also enable functionalization with active biomolecules. Herein we functionalized Na-MMT with epidermal growth factor (EGF) via ion exchange reaction to create a nanocomposite (MMT-EGF) with approximately 0.004 EGF molecules per Na(+) exchange site and conduct biochemical analyses of keratinocytes after treatment with MMT-EGF. Our results demonstrate that EGF immobilized on MMT retains the ability to activate the epidermal growth factor receptor (EGRF), causing phosphorylation of the AKT and MEK1 pathways, as well as upregulation of its downstream target gene expression involved in cell growth and migration. This study also shows that like EGF, MMT-EGF treatment can stimulate cell migration in vitro, which is dependent on ERK1/2 phosphorylation.
Biomacromolecules 08/2011; 12(9):3139-46. · 5.48 Impact Factor
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Small 05/2011; 7(9):1192-8. · 8.35 Impact Factor
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ABSTRACT: Monte Carlo simulations are performed to study the binding of peptides (M1: 1H2G3I4N5T6T7K8P9F10K11S12V) to a stack of mobile clay platelets and evaluate the morphological responses on a cubic lattice. A coarse-grained description is used to model both platelets and peptides capturing the specificity of each residue. Mobility profiles of residues and their proximity to platelets (i.e., the local structural profile) suggest that the peptide binding is anchored by 7Lys and 10Lys. Correlation between the density profiles of platelets and peptides aided by the visual analysis shows that (i) the layered morphology is maintained due to peptide binding, (ii) the interstitial spacing between platelets, that is, the gallery width decreases on increasing the peptide concentration (consistent with recent experiments), (iii) relatively smaller amplitude of oscillations in peptide density profile around the inner clay galleries suggests that the peptides are more likely to bind at the layer boundaries and exterior surface of the platelets than intercalate. The radius of gyration (Rg) of the peptide shows nonmonotonic dependence on the peptide concentration (Cp). © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010
Journal of Polymer Science Part B Polymer Physics 09/2010; 48(24):2566 - 2574. · 1.53 Impact Factor
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ABSTRACT: Here we report on the bioenabled assembly of layered nanohybrids using peptides identified with regard to their affinity to the nanoparticle surface. A dodecamer peptide termed M1, determined from a phage peptide display library, was found to bind to the surface of a layered aluminosilicate (montmorillonite, MMT). Fusion of a metal binding domain to the M1 peptide or the M1 peptide by itself was able to direct the growth of metal nanoparticles, such as gold and cobalt-platinum, respectively, on the MMT. This method of producing hybrid nanoclay materials will have utility in catalytic, optical, biomedical, and composite materials applications.
ACS Applied Materials & Interfaces 05/2010; 2(5):1492-8. · 4.53 Impact Factor
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Advanced Materials 01/2010; 22(1):115-9. · 13.88 Impact Factor
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ABSTRACT: Monte Carlo simulations are performed to study adsorption and desorption of coarse-grained peptide chains on generic gold and palladium surfaces in the presence of solvent. The atomistic structural details are ignored within the amino acid residues; however, their specificity and hydrophobicity are incorporated via an interaction matrix guided by atomistic simulation. Adsorption probabilities of the peptides A3, Flg, Pd2, Pd4, Gly10, Pro10 on gold and palladium surfaces are studied via analysis of the mobility of each residue, the interaction energy with the surface, profiles of the proximity to the surface, the radius of gyration, and comparisons to homopolymers. In contrast to the desorption of Gly10 and Pro10 (with faster global dynamics), peptides Pd2, Pd4, Flg, and A3 exhibit various degrees of adsorption on gold and palladium surfaces (with relatively slower dynamics). Adsorption on both gold and palladium occurs through aromatic anchoring residues Tyr2 and Phe12 in A3, Tyr2 in Flg, Phe2, His10 and His12 in Pd2, and His6 and His11 in Pd4. A lower (more negative) surface-interaction energy of these residues and lower mobility on palladium lead us to conclude that they are slightly more likely to be adsorbed on palladium surfaces than on gold.
Physical Chemistry Chemical Physics 04/2009; 11(12):1989-2001. · 3.57 Impact Factor
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ABSTRACT: Zinc oxide is a wide band gap material that has significant applications in photovoltaics, piezoelectrics and optoelectronics. Traditionally, ZnO has been synthesized using high temperatures and harsh reaction conditions. Recently, benign reaction conditions have been used to synthesize ZnO using amine and citrate additives. In this study, peptide phage display was performed to identify a peptide, termed Z1, that binds to and directs the growth of ZnO hexagonal nanocrystals. By altering the concentration of Z1 peptide, the ZnO nanocrystal morphology can be tailored. Additionally, Z1 peptide was used to direct the growth of ZnO structures on free-standing silk films. The results presented here demonstrate the utility of peptides in controlling the structure and deposition of ZnO.
Acta biomaterialia 01/2009; 5(3):876-82. · 3.98 Impact Factor
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ABSTRACT: Silk is an attractive biomaterial for use in tissue engineering applications because of its slow degradation, excellent mechanical properties, and biocompatibility. In this report, we demonstrate a simple method to cast patterned films directly from silk fibroin dissolved in an ionic liquid. The films cast from the silk ionic liquid solution were found to support normal cell proliferation and differentiation. The versatility of the silk ionic liquid solutions and the ability to process large amounts of silk into materials with controlled surface topography directly from the dissolved silk ionic liquid solution could enhance the desirability of biomaterials such as silk for a variety of applications.
Langmuir 02/2007; 23(3):1315-9. · 4.19 Impact Factor
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ABSTRACT: With the use of high-resolution transmission electron microscopy the structure and morphology of montmorillonite (MMT), a material of current interest for use in polymer nanocomposites, was characterized. Using both imaging theory and experiment, the procedures needed to generate lattice images from MMT were established. These procedures involve careful control of the microscope's objective lens defocus to maximize contrast from features of a certain size, as well as limiting the total dose of electrons received by the sample. Direct images of the MMT lattice were obtained from neat Na+ MMT, organically modified MMT, and organically modified MMT/epoxy nanocomposites. The degree of crystallinity and turbostratic disorder were characterized using electron diffraction and high-resolution electron microscopy (HREM). Also, the extent of the MMT sheets to bend when processed into an epoxy matrix was directly visualized. A minimum radius of curvature tolerable for a single MMT sheet during bending deformation was estimated to be 15 nm, and from this value a critical failure strain of 0.033 was calculated. HREM can be used to improve the understanding of the structure of polymer nanocomposites at the nanometer-length scale.
The Journal of Physical Chemistry B 10/2005; 109(38):17868-78. · 3.70 Impact Factor
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ABSTRACT: Several studies have demonstrated the use of biomimetic approaches in the synthesis of a variety of inorganic materials. Poly-L-lysine (PLL) promotes the precipitation of silica from a silicic acid solution within minutes. The molecular weight of PLL was found to affect the morphology of the resulting silica precipitate. Larger-molecular weight PLL produced hexagonal silica platelets, whereas spherical silica particles were obtained using low-molecular weight PLL. Here we report on the polypeptide secondary-structure transition that occurs during the silicification reaction. The formation of the hexagonal silica platelets is attributed to the PLL helical chains that are formed in the presence of monosilicic acid and phosphate ions. Hexagonal PLL crystals can also serve as templates in directing the growth of the silica in a manner that generates a largely mesoporous silica phase that is oriented with respect to the protein crystal template.
Journal of the American Chemical Society 10/2005; 127(36):12577-82. · 9.91 Impact Factor
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ABSTRACT: In this work, the suitability of imidazolium-based ionic liquid solvents is investigated for the dissolution and regeneration of silkworm (Bombyx mori) silk. Within an ionic liquid the anion plays a larger role in dictating the ultimate solubility of the silk. The dissolution of the silk in the ionic liquid is confirmed using wide-angle X-ray scattering. The dissolved silk is also processed into 100 mum-thick, two-dimensional films, and the structure of these films is examined. The rinse solvent, acetonitrile or methanol, has a profound impact on both the topography of the films and the secondary structure of the silk protein. The image depicts a silkworm cocoon dissolved in 1-butyl-3-methylimidazolium chloride and then regenerated as a film with birefringence.
Journal of the American Chemical Society 12/2004; 126(44):14350-1. · 9.91 Impact Factor
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ABSTRACT: The structure of thin films cast from regenerated solutions of Bombyx mori cocoon silk in hexafluoroisopropyl alcohol (HFIP) was studied by synchrotron X-ray diffraction during heating. A solid-state conformational transition from an alpha-helical structure to the well-known beta-sheet silk II structure occurred at a temperature of approximately 140 degrees C. The transition appeared to be homogeneous, as both phases do not coexist within the resolution of the current study. Modulated differential scanning calorimetry (DSC) of the films showed an endothermic melting peak followed by an exothermic crystallization peak, both occurring near 140 degrees C. Oriented fibers were also produced that displayed this helical molecular conformation. Subsequent heating above the structural transition temperature produced oriented beta-sheet fibers very similar in structure to B. mori cocoon fibers. Heat treatment of silk films at temperatures well below their degradation temperature offers a controllable route to materials with well-defined structures and mechanical behavior.
Biomacromolecules 6(6):3328-33. · 5.48 Impact Factor
