Development of thermosensitive hydrogels of chitosan, sodium and magnesium glycerophosphate for bone regeneration applications.

Thermosensitive injectable hydrogels based on chitosan neutralized with sodium beta-glycerophosphate (Na-ß-GP) have been studied as biomaterials for drug delivery and tissue regeneration. Magnesium (Mg) has been reported to stimulate adhesion and proliferation of bone forming cells. With the aim of improving the suitability of the aforementioned chitosan hydrogels as materials for bone regeneration, Mg was incorporated by partial substitution of Na-ß-GP with magnesium glycerophosphate (Mg-GP). Chitosan/Na-ß-GP and chitosan/Na-ß-GP/Mg-GP hydrogels were also loaded with the enzyme alkaline phosphatase (ALP) which induces hydrogel mineralization. Hydrogels were characterized physicochemically with respect to mineralizability and gelation kinetics, and biologically with respect to cytocompatibility and cell adhesion. Substitution of Na-ß-GP with Mg-GP did not negatively influence mineralizability. Cell biological testing showed that both chitosan/Na-ß-GP and chitosan/Na-ß-GP/Mg-GP hydrogels were cytocompatible towards MG63 osteoblast-like cells. Hence, chitosan/Na-ß-GP/Mg-GP hydrogels can be used as an alternative to chitosan/Na-ß-GP hydrogels for bone regeneration applications. However the incorporation of Mg in the hydrogels during hydrogel formation did not bring any appreciable physicochemical or biological benefit.