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Photo-polymerized hydrogels are ideally suited for stem-cell based tissue regeneration and three dimensional (3D) bioprinting because they can be highly biocompatible, injectable, easy to use, and their mechanical and physical properties can be controlled. However, photo-polymerization involves the use of potentially toxic photo-initiators, exposure to ultraviolet light radiation, formation of free radicals that trigger the cross-linking reaction, and other events whose effects on cells are not yet fully understood. The purpose of this study was to examine the effects of hydrogen sulfide (H2S) in mitigating cellular toxicity of photo-polymerization caused to resident cells during the process of hydrogel formation. H2S, which is the latest discovered member of the gasotransmitter family of gaseous signalling molecules, has a number of established beneficial properties, including cell protection from oxidative damage both directly (by acting as a scavenger molecule) and indirectly (by inducing the expression of anti-oxidant proteins in the cell). Cells were exposed to slow release H2S treatment using pre-conditioning with glutathione-conjugated-garlic extract in order to mitigate toxicity during the photo-polymerization process of hydrogel formation. The protective effects of the H2S treatment were evaluated in both an enzymatic model and a 3D cell culture system using cell viability as a quantitative indicator. The protective effect of H2S treatment of cells is a promising approach to enhance cell survival in tissue engineering applications requiring photo-polymerized hydrogel scaffolds. [ABSTRACT FROM AUTHOR]

The design of biomaterial platforms able to release bioactive molecules is mandatory in tissue repair and regenerative medicine. In this context, electrospinning is a user-friendly, versatile and low-cost technique, able to process different kinds of materials in micro- and nano-fibers with a large surface area-to-volume ratio for an optimal release of gaseous signaling molecules. Recently, the antioxidant and anti-inflammatory properties of the endogenous gasotramsmitter hydrogen sulfide (H2S), as well as its ability to stimulate relevant biochemical processes on the growth of mesenchymal stem cells (MSC), have been investigated. Therefore, in this work, new poly(lactic) acid fibrous membranes (PFM), doped and functionalized with H2S slow-releasing donors extracted from garlic, were synthetized. These innovative H2S-releasing mats were characterized for their morphological, thermal, mechanical, and biological properties. Their antimicrobial activity and effects on the in vitro human cardiac MSC growth, either in the presence or in the absence of oxidative stress, were here assessed. On the basis of the results here presented, these new H2S-releasing PFM could represent promising and low-cost scaffolds or patches for biomedical applications in tissue repair. [ABSTRACT FROM AUTHOR]