A multifunctional hydrogen sulfide-releasing microparticle/hydrogel hybrid for biomedical applications.

Hydrogen sulfide (H2S) has been recognized as one of the three main gasotransmitters found extensively in tissues, regulating functions crucial for survival. In many pathological cases, its concentration drops from the intrinsic level, impairing healing and leading to unmet regeneration outcomes. A hybrid microparticle/hydrogel system was developed to sustainably release H2S and regulate its level in deprived tissues. To synthesize the microparticles, polyglycerol sebacate-polyethylene glycol copolymer (PGSE) was prepared by high temperature-low pressure polycondensation and characterized by ATR-FTIR, 1H NMR, and GPC. Urethane-crosslinked microparticles loaded with sodium hydrosulfide (NaHS) were synthesized using a double emulsion solvent evaporation technique. The morphology, size (20.30 ± 6.73 µm), and encapsulation efficiency (52.16 ± 5.20 %) of particles were characterized by SEM and ICP-EOS. The particles showed a 5-day sustained release profile, detected by spectrophotometry. They were then incorporated into a conductive semi-IPN hydrogel. The conductive κ-carrageenan-polypyrrole polymer was synthesized by oxidation polymerization and characterized by ATR-FTIR, 1H NMR, UV-vis, and TGA. The polymer was integrated into a GelMA/PEGDA photocrosslinked hydrogel, characterized by SEM (pore size 73.72 ± 30.21 µm), ATR-FTIR, and frequency sweep test. The particle-loaded hydrogel (GEPD/KCPS) showed swelling ratio, conductivity, and antioxidant activity of 4.4 ± 0.13, 13.21 mS/m, and 21.5 ± 2.55 %, respectively. The composite released H2S over 5 days with a cumulative release of 92.33 ± 7.22 %. This multifunctional system could be applied to electro-responsive tissues needing H2S for regeneration.