Abstract: BACKGROUND: Oxidized hydroxypropyl methylcellulose-sodium hyaluronate hydrogel system exerts perfect mechanical properties, biocompatibility, and degradability, can be employed as a tissue engineered scaffold to protect and support injured tissues, and can also be applied as a drug carrier to achieve a regional sustained-release effect.
OBJECTIVE: To prepare sustained-release antibacterial microsphere composite tissue-engineered material hydrogel, and investigate its physical and chemical, biological, osteoinductive, and antibacterial properties.
METHODS: Using poly(lactic-co-glycolicacid), chitosan, and sodium hyaluronate as materials, a porous microsphere carrier with a multilayer structure was prepared by the emulsion method. Vancomycin hydrochloride was loaded to prepare sustained-release antibacterial microspheres. Oxidized hydroxypropyl methylcellulose-hydrazide-modified sodium hyaluronate was utilized as the matrix to prepare an injectable hydrogel. Different mass concentrations of antibacterial sustained-release microspheres (0.1, 0.2, and 0.3 g/mL) were added to the hydrogel to prepare an injectable hydrogel containing sustained-release antibacterial microspheres. The physical and chemical properties (determination of gel-forming time, swelling performance, degradation performance), biological properties (cytotoxicity, cell hemolysis), and osteogenic properties (alkaline phosphatase activity and osteogenic genes RUN-x2, bone morphogenetic protein 2, osteocalcin, type I collagen expression levels), and antibacterial properties were tested and evaluated.  
RESULTS AND CONCLUSION: (1) The three kinds of sustained-release antibacterial microsphere hydrogels had good gel-forming properties and a small swelling ratio. The in vitro degradation scanning electron microscope results exhibited that the hydrogels had stable self-degradation properties. (2) The cytotoxicity experiment displayed that when the added number of sustained-release antibacterial microspheres was less than or equal to 0.2 g/mL, the hydrogel did not have remarkable cytotoxicity (the relative growth rate of cells within 7 days was all greater than 80%). The hemolysis experiment demonstrated that cell hemolysis rate of three kinds of the sustained-release antibacterial microsphere hydrogel was less than 2%, without obvious cell hemolysis. (3) Three kinds of sustained-release antibacterial microsphere hydrogels could increase the osteogenic gene RUN-x2, bone morphogenetic protein 2, type I collagen, osteocalcin contents, and alkaline phosphatase production in MG-63 cells. (4) These hydrogels could suppress the growth of Staphylococcus aureus continuously and for a long time, and the antibacterial ability of the hydrogels increased with the increased amount of sustained-release antibacterial microspheres. (5) These results show that the prepared injectable antibacterial microsphere hydrogel has perfect sustained-release antibacterial, osteogenic, and osteoinductive capabilities, as well as good biohistocompatibility and degradability. 

Key words: antibacterial microsphere, vancomycin hydrochloride, hydrogel, property, poly(lactic-co-glycolicacid), chitosan, sodium hyaluronate, osteomyelitis