Dual-Functional Implant Based on Gellan-Xanthan Hydrogel with Diopside, BMP-2 and Lysostaphin for Bone Defect Repair and Control of Staphylococcal Infection

A new dual-functional implant based on gellan-xanthan hydrogel with calcium-magnesium silicate ceramic diopside and recombinant lysostaphin and bone morphogenetic protein 2 (BMP-2)-ray is developed. In this composite, BMP-2 is immobilized on microparticles of diopside while lysostaphin is mixed directly into the hydrogel, providing sustained release of BMP-2 to allow gradual bone formation and rapid release of lysostaphin to eliminate infection immediately after implantation. Introduction of diopside of up to 3% (w/v) has a negligible effect on the mechanical properties of the hydrogel but provides a high sorption capacity for BMP-2. The hydrogels show good biocompatibility and antibacterial activity. Lysostaphin released from the implants over a 3 h period efficiently kills planktonic cells and completely destroys 24 h pre-formed biofilms of Staphylococcus aureus. Furthermore, in vivo experiments in a mouse model of critically-sized cranial defects infected with S. aureus show a complete lack of osteogenesis when implants contain only BMP-2, whereas, in the presence of lysostaphin, complete closure of the defect with newly formed mineralized bone tissue is observed. Thus, the new implantable gellan-xanthan hydrogel with diopside and recombinant lysostaphin and BMP-2 shows both osteogenic and antibacterial properties and represents a promising material for the treatment and/or prevention of osteomyelitis after bone trauma.