Biodegradable, crosslinked silicone-gelatin hydrogels

Silicone-protein elastomers form with crosslinking provided by HCHO. The resulting product undergoes enzymatic degradation in 1–2 weeks to give silicone oils and protein fragments. Elastomers, including thermoset silicone rubbers, are known for exceptional stability, which compromises their circularity; these materials are not expected to undergo facile degradation in the environment. Crosslinkers based on the protein gelatin were examined as a strategy to facilitate the biological degradation of silicone elastomers at end of life. Silicone hydrogels were prepared from aminopropylsilicones in ratios of gelatin : silicone from 33 : 67 → 67 : 33 and fixed using formaldehyde. The physical properties of the copolymers depend on the degree of hydration, crosslink density and ratio of constituents, and follow an expected correlation with crosslink density. The products undergo degradation catalyzed by the enzyme bromelain to permit the recovery of protein fragments in the aqueous phase and, separately, silicone oils modified by protein constituents, suggesting that environmental decomposition may also be possible.