Hydrogel-elastomer composite biomaterials: 1. Preparation of interpenetrating polymer networks and in vitro characterization of swelling stability and mechanical properties.

We prepared interpenetrating polymer networks (IPNs) composed of a gelatin hydrogel and a HydroThane elastomer to combine the advantages of both polymers into one biomaterial. Fourier transform Infrared (FTIR) spectroscopy and Differential Scanning Calorimetry (DSC) confirmed the co-existence of the two polymers in the IPNs. Optical light microscopy confirmed hydrogel domains were interspaced into an elastomer network. Hydration and stability studies in aqueous solution showed that, although the IPN biomaterials exhibited stable swelling for more than 30 days, approximately 10% and 50% loss of the hydrogel component were confirmed at room temperature and 37 degrees C, respectively, using gel permeation chromatography (GPC). The swelling study in the serum-containing medium indicated the biomaterials maintained their swelling stability for different periods, depending on the extent of gelatin methacrylation, photoinitiator concentration and incubation temperature. Lastly, the biomaterials exhibited higher failure stress and lower failure strain in a dry state than in a swollen state, and showed limited changes in both stress and strain at room temperature and at 37 degrees C, in contrast with a decrease at 50 degrees C. No significant effects of gelatin methacrylation on mechanical properties were noticed. The preparation and characterization methods were well established and formed the basis of further developing the biomaterials.