Antibacterial and osteogenic carbon quantum dots for regeneration of bone defects infected with multidrug-resistant bacteria

Intractable bacterial infections and insufficient osseointegration are two major concerns plaguing the repair of infected bone defects. Many attempts use antibiotics coatings on the implant surface to prevent infectious biofilm formation and promote bone regeneration, however, the introduction of toxic antibiotics not only leads to the appearance of multidrug-resistant (MDR) bacteria, but also decreases osteoinductivity of scaffold materials. Herein, we report for the first time the systemic regulation of the antibacterial and osteogenic activities of carbon quantum dots (CQDs) by changing their surface charge. The positively charged CQDs (p-CQDs) exhibited excellent antibacterial activity against MDR bacteria and suppression of biofilm formation, whereas negatively charged CQDs (n-CQDs) could significantly promoted bone regeneration. To avoid aggregation of p-CQDs and n-CQDs in scaffolds, we first fabricated nearly neutral p-CQD/WS2 hybrids by depositing p-CQDs on WS2 nanosheets (NSs). We then constructed a multifunctional biodegradable p-CQD/WS2 and n-CQDs co-encapsulated GelMA hydrogel scaffolds. In a MRSA-infected craniotomy defect model, implantation of multifunctional p-CQD/WS2/n-CQD/GelMA hydrogel scaffolds resulted in nearly complete repair of infected bone defect with the new bone area of 97.0 ± 1.6% at 60 days. These findings indicate a surface charge regulation strategy for designing biomaterials with both antibacterial and osteogenic activities for treating infected bone defects.