Silk fibroin porous scaffolds loaded with a slow-releasing hydrogen sulfide agent (GYY4137) for applications of tissue engineering

Hydrogen sulfide (H2S) is a physiological gasotransmitter known to possess a regulatory role in several tissues, including bone. The exogenous administration by injection of solutions of H2S-releasing compounds (e.g., GYY4137) has been previously investigated as a novel therapeutic approach for the treatment of bone diseases. Here, GYY4137 was embedded into fibroin sponges, previously shown to be suitable as scaffolds for bone, thanks to their biocompatibility, scalable porous structure, and biodegradability rate. Fibroin porous scaffolds were produced by solvent casting and the particulate leaching method, and GYY4137 was successively incorporated by using dimethyl sulfoxide (DMSO) as vehicle. The process used to produce GYY4137-loaded scaffolds allowed the incorporation of different controlled amounts of GYY4137 into fibroin matrices. The loading process preserved the properties of the system components in the final products, as assessed by SEM, FT-IR, NMR, and different thermal analyses techniques. Release of H2S from GYY4137 incorporated into the scaffolds was monitored upon incubation in saline solution at physiological pH: H2S-release kinetic was found to be dependent on the amount of GYY4137. To ensure biocompatibility, mouse fibroblasts and human primary bone marrow stromal cells were seeded onto scaffolds, and short-term viability assays were performed. Results showed that the GYY4137-loaded scaffold did not induce cytotoxicity in any of the cell type tested. Our findings demonstrate that embedding an H2S-releasing donor in silk fibroin scaffold is a suitable strategy to achieve a long-lasting release of H2S that preserves cell viability and allows local delivery at sites of tissue injury.