Recombinant Protein-co-PEG Networks as Cell-Adhesive and Proteolytically Degradable Hydrogel Matrixes. Part II:  Biofunctional Characteristics

Abstract

We present here the biological performance in supporting tissue regeneration of hybrid hydrogels consisting of genetically engineered protein polymers that carry specific features of the natural extracellular matrix, cross-linked with reactive poly(ethylene glycol) (PEG). Specifically, the protein polymers contain the cell adhesion motif RGD, which mediates integrin receptor binding, and degradation sites for plasmin and matrix-metalloproteinases, both being proteases implicated in natural matrix remodeling. Biochemical assays as well as in vitro cell culture experiments confirmed the ability of these protein-PEG hydrogels to promote specific cellular adhesion and to exhibit degradability by the target enzymes. Cell culture experiments demonstrated that proteolytic sensitivity and suitable mechanical properties were critical for three-dimensional cell migration inside these synthetic matrixes. In vivo, protein-PEG matrixes were tested as a carrier of bone morphogenetic protein (rhBMP-2) to heal critical-sized defects in a rat calvarial defect model. The results underscore the importance of fine-tuning material properties of provisional therapeutic matrixes to induce cellular responses conducive to tissue repair. In particular, a lack of rhBMP or insufficient degradability of the protein-PEG matrix prevented healing of bone defects or remodeling and replacement of the artificial matrix. This work confirms the feasibility of attaining desired biological responses in vivo by engineering material properties through the design of single components at the molecular level. The combination of polymer science and recombinant DNA technology emerges as a powerful tool for the development of novel biomaterials.

Peptide-based biopolymers in biomedicine and biotechnology

“…A similar bone volume was measured in Group II, but the bone was confined at matrix surface. Reproduced from [285]. [369].…”

“…The Hubbell group has turned their attention to designing and synthesizing hydrogels that mimic the bi-directional biomolecular interactions that naturally occur between cells and the extracellular matrix (ECM) surrounding them [184,[273][274][275][276][277][278][279][280][281][282][283][284][285]. They have found that signals such as cell adhesion sites, bound growth factors, and cleavage sites for proteolytic activity are essential for cells to be able to remodel the ECM and sustain tissue regeneration.…”

“…In the second class of hydrogels, chemically crosslinked three-dimensional networks are formed by Michael-type addition reactions between thiol-bearing bioactive peptides and conjugated unsaturations on single-or multi-armed poly(ethylene glycol (PEG) chains endfunctionalized with vinyl sulfone [273,[279][280][281][282][283][284][285]. In studies by Rizzi et al, peptide sequences containing multiple cysteine residues, integrin-binding RGD domains, and substrates for degradation by the cell-secreted proteases matrix metalloproteinase (MMP) and plasmin were synthesized recombinantly [284,285].…”

“…In studies by Rizzi et al, peptide sequences containing multiple cysteine residues, integrin-binding RGD domains, and substrates for degradation by the cell-secreted proteases matrix metalloproteinase (MMP) and plasmin were synthesized recombinantly [284,285]. The cysteine residues provide reactive thiols for conjugation to synthetically polymerized vinyl sulfone-terminated PEG.…”

Peptide- and protein-mediated assembly of heparinized hydrogels

“…[1][2][3][4][5][6][7][8][9][10][11] The high water content, biocompatibility, nonfouling properties, and mechanically robust nature of many of these hydrogels has also continued to motivate their investigation. Synthetic polymers such as poly(ethylene glycol) (PEG), poly(vinyl alcohol), poly(N-isoproprylacrylamide), poly(lactic-co-glycolic acid) (PLGA), and copolymers of these and other polymers have provided many useful systems for application in biomedical areas, but are often hindered by their lack of biological activity.…”