Structural and functional characterization of biosynthetic PVA-gelatin hydrogels designed for cell based therapy
The addition of biological molecules to cell immunoisolation devices can significantly enhance their performance by supporting cell viability and function. However, the impact of adding biologics on the physical structure and subsequent permselectivity of such devices to nutrients and immune system components has not been extensively studied. The aim of this study was to investigate the effect of incorporating gelatin on the network structure and permeability of synthetic poly (vinyl alcohol) (PVA) hydrogels and to assess the bioactivity of gelatin after incorporation. PVA was functionalized with an average of 7 and 20 methacrylate functional groups per chain (FG/c) while gelatin was functionalized with ~13 FG/c. Hydrogels were fabricated with PVA:gelatin ratios of 19:1 or 15:5 via UV photopolymerization and were characterized for network parameters. The cell adhesive functionality of gelatin was assessed for composite hydrogels using L929 fibroblasts. Permeability of biosynthetic hydrogels to bovine serum albumin (BSA) and immunoglobulin G (IgG) was examined. In all PVA and composite hydrogels, % sol fraction was less than 20% with a significant decrease in Q values observed when FG/c increased from 7 to 20. This decrease in swelling correlated with the reduction in mesh size from ~ 100 Å(7 FG/c) to 55 Å(20 FG/c). In composite gels, 70-90% of gelatin remained incorporated after 7 days of swelling. Gelatin retained its cell binding functionality at low percent incorporation and showed equivalent results to pure gelatin gels. While the permeation profiles of both BSA and IgG were not affected by the addition of gelatin as compared to pure PVA, increasing the FG/c from 7 to 20 significantly limited the diffusion of the larger IgG. Consequently, biosynthetic hydrogels composed of PVA with high FG/c and low percent gelatin show promise to be applied for immunoisolation of transplanted mammalian cells in cell based therapies.
KeywordsPVA gelatin hydrogels cell therapy permeability
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