Antimicrobial drug-derived carbon quantum dots for photodynamic therapy of bedsores and bacterial infections.

Objectives: Bedsores (pressure ulcers) exhibit high incidence rates (0.4-38%) and prolonged recovery periods, with bacterial infections posing the most frequent and severe complications, significantly impeding wound healing. Conventional antibiotic therapies face limitations due to antimicrobial resistance, necessitating innovative strategies with enhanced biocompatibility and reduced resistance-inducing potential. This study aimed to develop a photodynamic therapy (PDT)-based antimicrobial approach by converting antimicrobial drugs into N-doped carbon quantum dots (N, CQ-dots) for efficient bacterial inhibition in wound environments.

Methods: N, CQ-dots were synthesized from protocatechuic acid (a natural antimicrobial metabolite) via solvothermal method, preserving critical functional groups (-COOH, -OH) inherited from the precursor. Structural and optical properties were characterized using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and ultraviolet-to-visible (UV-Vis) spectroscopy. Photodynamic antimicrobial efficacy was evaluated against Staphylococcus aureus and Escherichia coli through colony-count assays, and live/dead staining.

Results: The synthesized N, CQ-dots exhibited uniform morphology (~3.5 nm) and abundant oxygen-containing functional groups, as confirmed by XPS and Fourier Transform Infrared (FTIR) spectrometer analysis. Under irradiation, the material demonstrated potent antibacterial activity, achieving >99.9% viability reduction in Gram-positive and Gram-negative strains, with minimal cytotoxicity (MBC >100 μg/mL).

Conclusions: This work demonstrates a novel paradigm for transforming antimicrobial drugs into multifunctional N, CQ-dots, leveraging preserved pharmacophores and PDT mechanisms to overcome drug resistance. The system combines intrinsic antibacterial activity with light-triggered responsiveness, offering a promising solution for managing infected bedsores while minimizing systemic toxicity. These findings highlight the translational potential of drug-derived nanomaterials in precision wound care.