Recombinant protein-co-PEG networks as cell-adhesive and proteolytically degradable hydrogel matrixes. Part I: Development and physicochemical characteristics.
ABSTRACT Toward the development of synthetic bioactive materials to support tissue repair, we present here the design, production, and characterization of genetically engineered protein polymers carrying specific key features of the natural extracellular matrix, as well as cross-linking with functionalized poly(ethylene glycol) (PEG) to form hybrid hydrogel networks. The repeating units of target recombinant protein polymers contain a cell-binding site for ligation of cell-surface integrin receptors and substrates for plasmin and matrix metalloproteinases (MMPs), proteases implicated in wound healing and tissue regeneration. Hydrogels were formed under physiological conditions via Michael-type conjugate addition of vinyl sulfone groups of end-functionalized PEG with thiols of cysteine residues, representing designed chemical cross-linking sites within recombinant proteins. Cross-linking kinetics was shown to increase with the pH of precursor solutions. The elastic moduli (G') and swelling ratios (Q(m)) of the resulting hydrogels could be varied as a function of the stoichiometry of the reacting groups and precursor concentration. Optima of G' and Q(m), maximum and minimum, respectively, were obtained at stoichiometry ratios r slightly in excess of 1 (r = cysteine/vinyl sulfone). The pool of technologies utilized here represents a promising approach for the development of artificial matrixes tailored for specific medical applications.
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ABSTRACT: The supramolecular design of bioactive artificial extracellular matrices to control cell behavior is of critical importance in cell therapies and cell assays. Most previous work in this area has focused on polymers or monolayers which preclude control of signal density and accessibility in the nanoscale filamentous environment of natural matrices. We have used here self-assembling supramolecular nanofibers that display the cell adhesion ligand RGDS at van der Waals density to cells. Signal accessibility at this very high density has been varied by changes in molecular architecture and therefore through the supramolecular packing of monomers that form the fibers. We found that branched architectures of the monomers and the consequent lower packing efficiency and additional space for epitope motion improves signaling for cell adhesion, spreading, and migration. The use of artificial matrices with nanoscale objects with extremely high epitope densities could facilitate receptor clustering for signaling and also maximize successful binding between ligands and receptors at mobile three-dimensional interfaces between matrices and cells. Supramolecular design of artificial bioactive extracellular matrices to tune cell response may prove to be a powerful strategy in regenerative medicine and to study biological processes.Biomaterials 12/2007; 28(31):4608-18. DOI:10.1016/j.biomaterials.2007.06.026 · 8.31 Impact Factor
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ABSTRACT: The nanometer-scale mesh size of many synthetic crosslinked hydrogel networks restricts encapsulated cells to a rounded morphology that can inhibit cellular processes such as proliferation and migration that are essential for the early stages of remodeling and tissue formation. The objective of these studies was to investigate an approach for accelerating cellular remodeling based on the creation of semi-interpenetrating networks (IPNs) composed of hydrolytically degradable poly(ethylene glycol) (PEG) diacrylate macromers and native, enzymatically degradable extracellular matrix (ECM) components (collagen, gelatin and hyaluronic acid (HA)). Among the three ECM components investigated, addition of HA at concentrations of 0.12% w/v and greater supported fibroblast spreading throughout the three-dimensional network and significantly increased proliferation relative to control hydrogels without HA. Incorporation of HA resulted in relatively small changes in hydrogel physical/chemical properties such as swelling, degradation rate, and elastic modulus. Fibroblast spreading was eliminated by the addition of hyaluronidase inhibitors, demonstrating that cell-mediated enzymatic degradation of HA is a necessary mechanism responsible for the observed increases in fibroblast activity. By accelerating early cellular remodeling and growth, these semi-IPNs may be useful vehicles for cell transplantation in a variety of tissue engineering applications.Biomaterials 12/2007; 28(33):4928-38. DOI:10.1016/j.biomaterials.2007.08.007 · 8.31 Impact Factor
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ABSTRACT: Regenerative medicine strategies for restoring articular cartilage face significant challenges to recreate the complex and dynamic biochemical and biomechanical functions of native tissues. As an approach to recapitulate the complexity of the extracellular matrix, collagen-mimetic proteins offer a modular template to incorporate bioactive and biodegradable moieties into a single construct. We modified a Streptococcal collagen-like 2 protein with hyaluronic acid (HA) or chondroitin sulfate (CS)-binding peptides and then cross-linked with a matrix metalloproteinase 7 (MMP7)-sensitive peptide to form biodegradable hydrogels. Human mesenchymal stem cells (hMSCs) encapsulated in these hydrogels exhibited improved viability and significantly enhanced chondrogenic differentiation compared to controls that were not functionalized with glycosaminoglycan-binding peptides. Hydrogels functionalized with CS-binding peptides also led to significantly higher MMP7 gene expression and activity while the HA-binding peptides significantly increased chondrogenic differentiation of the hMSCs. Our results highlight the potential of this novel biomaterial to modulate cell-mediated processes and create functional tissue engineered constructs for regenerative medicine applications. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.Biomaterials 06/2015; 54. DOI:10.1016/j.biomaterials.2015.02.079 · 8.31 Impact Factor