Abstract: Objective · To construct a novel antibacterial and injectable hydrogel (BMP/Gel/SH-Ag) loaded with bone morphogenetic protein-2 (BMP-2) microspheres, and investigate its biocompatibility, antibacterial properties and bone-promoting properties. Methods · The photocrosslinked gelatin microspheres loaded with BMP-2 were prepared by microfluidics. The microspheres were mixed with 4-arm thiol-terminated poly (ethylene glycol) (4SH-PEG) and crosslinked with Ag+ to prepare injectable sulfhydrylated PEG hydrogels (BMP/Gel/SH-Ag). The micromorphology of microspheres and hydrogels was observed by light microscope and scanning electron microscope. The drug release profile was investigated at 37 ℃ in a shaker (100 r/min). The injectability of BMP/Gel/SH-Ag was evaluated by injecting hydrogel using a syringe with a tip diameter of 0.5 mm. The antibacterial activity of BMP/Gel/SH-Ag against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) was evaluated by agar diffusion test. The biocompatibility of BMP/Gel/SH-Ag was verified by CCK-8, and the bone-promoting activity was evaluated by alkaline phosphatase (ALP) assay and calcium nodule staining in bone marrow mesenchymal stem cells (BMSCs). Results · Gelatin microspheres had smooth appearance and uniform particle size distribution (～ 350 μm). BMP/Gel/SH-Ag had porous microstructure and can be injected with a syringe needle with a diameter of up to 0.5 mm in diameter to produce hydrogel filament. The cumulative release of BMP-2 from BMP/Gel/SH-Ag was (81.8±3.6)% after being incubated for 8 d. BMP/Gel/SH-Ag had obvious inhibitory effect on S. aureus and E. coli. CCK-8 results showed that BMP/Gel/SH-Ag had good biocompatibility. BMP/Gel/SH-Ag can increase the expression of ALP and the content of calcium nodules in rat BMSCs. Conclusion · The BMP/Gel/SH-Ag has good performance in promoting osteogenesis and anti-infection.

Key words: microfluidics, microsphere, bacteriostasis, injectable hydrogel, promoting osteogenesis