Analysis of oxidative degradation and calcification behavior of a silicone polycarbonate...

The biocompatibility and chemical stability of implantable devices are crucial for their long-term success. CarboSil® is a silicon polycarbonate polyurethane copolymer with good biocompatibility and biostability properties. Here, we explored the possibility to improve these characteristics by introducing 30% of extra-chain cross-linkable poly(dimethyl siloxane) (PDMS). Patches made of CarboSil and CarboSil-30% PDMS were manufactured by spray, phase-inversion technique and subjected to a heating-pressure treatment. Both materials showed good biocompatibility, either in viability and proliferation of cell-based experiments both with mouse fibroblasts and subcutaneous implant in rats. Fourier-transform infrared spectroscopy showed a significant decrease in soft segment loss in CarboSil-30% PDMS samples with respect to CarboSil in in vitro accelerated oxidative treatments with CoCl₂ and 20% H₂ O₂ at 37°C up to 36 days. Same results were observed in subcutaneous implants up to 90 days. Field-emission scanning electron microscopy on samples exposed to calcification solutions during 80 days highlighted the presence of a homogeneous distribution of calcium deposition over the entire surface of CarboSil samples, while no calcium deposits were observed in CarboSil-30% PDMS samples. Patches subjected to subcutaneous experiments showed no sign of calcification after 90 days, irrespectively of their composition. Thanks to the improved characteristics in terms of degradation and calcification the modified materials described in this work hold great promise for their use in the manufacture of cardiovascular devices.