Effect of the injectable alginate/ nano-hydroxyapatite and the silica/ nano-hydroxyapatite composites on the stem cells: a comparative study

Self-setting bone pastes are currently attracting considerable attention in the field of treating damaged bones. In this study, natural nano-hydroxyapatite enriched with trace elements was combined with silica (SiO2/n-HA) or natural alginate (Alg/n-HA) to innovate biocomposite injectable hydrogels. The injectable pastes' porosity, viscosity, setting time, and mechanical properties were tested. Moreover, in-vitro characteristics and the influence of the developed injectable hydrogels on the cytocompatibility of mesenchymal stem cells were also studied. According to the results, the type of hydrogel incorporated with nano-hydroxyapatite had a significant influence on the physicomechanical properties. The Alg/n-HA had higher mechanical and viscosity properties reached to 6.31 MPa and 1680 Pa-S in comparison to 2.93 MPa and 1415 Pa-S for SiO2/n-HA, respectively. Otherwise, SiO2/ n-HA had higher biodegradability and water absorption. Cytocompatibility assays results showed that mesen-chymal stem cell viability exceeded 70% for all dilutions of n-HA, Alg/n-HA and SiO2/n-HA at all observation points, also the tested hydrogels promoted wound healing at closure rates that were significantly higher than the control group at all observation points (p<0.05). Complete wound closure was observed for Alg/n-HA and SiO2/ n-HA after 72 h.