On the influence of graphene oxide and hydroxyapatite modification on alginate-based hydrogel matrix: thermal, physicochemical, and biological considerations

Sodium alginate (SA) hydrogels with an addition of graphene oxide (GO) and hydroxyapatite (HAp) crosslinked by calcium chloride solution were investigated as potential materials for osteochondral tissue regeneration. The influence of various ratios of the nanoadditives in the natural derived polymer matrix on the thermal, physiochemical and biological properties was studied. Two thermal characterization methods (DSC and TGA) were employed to examine the thermal properties of the materials and provide information regarding the different types of water within the hydrogel structure. These parameters are crucial for the assessing and understanding of the adsorption/desorption processes in hydrogels and also impact their biocompatibility. The effect of GO and HAp addition on thermal characteristics of alginate hydrogel is reported, as well as the nanoadditives polymer chains interaction, as evidenced by FTIR results. The compression test confirmed that the nanoadditives, uniformly dispersed in the polymer matrix, improved the mechanical properties of the hydrogels, but only up to a certain content of additives. The composite hydrogels exhibited a very low friction coefficient. Both GO and HAp also enhanced chemical stability of alginate hydrogels under in vitro conditions. Biological assays demonstrated that most of the tested hydrogel extracts were not cytotoxic to hUC-MSCs, but they can affect the proliferation rate of the cells. Developed materials may present an intriguing alternative for osteochondral tissue regeneration.