Injectable Electrospun Hydrogel with Antimicrobial, pH Sensing Nanoparticles for Local Infection Control and Monitoring

Most antimicrobial drug candidates currently in development are derivatives of established antibiotic classes. In contrast, antimicrobial heteroatom-doped carbon quantum dot (CǪD) nanoparticles vastly differ from their chemical antibiotic counterparts and exhibit potent antibacterial activity and favourable biocompatibility, representing a promising alternative strategy, particularly for topical applications. Here, we report the incorporation of cobalt-doped carbon quantum dots (Co-CǪDs) into injectable, biocompatible hydrogels capable of both sensing pH and eliminating bacteria. Ultrasmall Co-CǪDs demonstrated broad-spectrum activity against gram-positive Methicillin-resistant Staphylococcus aureus (MRSA) and Gram-negative Pseudomonas aeruginosa (PAO1), mediated by membrane hyperpolarisation and reactive oxygen species (ROS) induced membrane damage. The particles showed negligible effect on primary fibroblast and endothelial cell viability at concentrations that were bactericidal to MRSA. Polymeric hydrogels were fabricated via electrospinning of chitosan, polyvinylpyrrolidone (PVP), and polyvinyl alcohol (PVA) polymer blends incorporating Co-CǪD and pH-responsive HPTS particles. This approach provided accurate measurement of environmental pH within the physiological range observed across healthy and chronic wounds. In vivo , the injectable hydrogels exhibited robust antimicrobial efficacy against MRSA without impairing wound closure relative to untreated controls, while also reducing inflammatory immune responses in infected tissues. Collectively, these findings demonstrate the potential of ultrasmall metal-doped CǪDs for infection control and their integration into 3D matrices as multifunctional theragnostic platforms.