Adjustment of the antibacterial activity and biocompatibility of hydroxypropyltrimethyl ammonium chloride chitosan by varying the degree of substitution of quaternary ammonium

Hydroxypropyltrimethyl ammonium chloride chitosan (HACC) was synthesised with differing degrees of substitution (6%, 18% and 44%) of quaternary ammonium by reacting chitosan with glycidyl trimethylammonium chloride. The antibacterial activities of these polymers were tested in vitro against Staphylococcus aureus, Methicillin-resistant Staphylococcus aureus, and Staphylococcus epidermidis. Mouse fibroblasts and bone marrow derived stromal cells (hMSCs) were used to investigate the biocompatibility of the HACC. The results show that the antibacterial activities of the HACC with 18% or 44% substitution were significantly higher than the others (P < 0.05) against all three bacteria. HACC with 6% or 18% substitution was not cytotoxic and did not interfere with the proliferation and osteogenic differentiation of hMSCs. Overall, we can make a conclusion that HACC with an 18% substitution was a potential pharmaceutical that can inhibit the growth of bacteria and has good biocompatibility with osteogenic cells.