The effect of photodynamic therapy using gentamicin and imipenem-derived carbon dots on Pseudomonas aeruginosa isolates.

The increasing prevalence of antibiotic resistance poses a significant threat to the ability of healthcare systems to manage Pseudomonas aeruginosa infections, highlighting the need for innovative therapeutic strategies. The aim of this study was to evaluate the effects of photodynamic therapy (PDT) using carbon dots (CDs) derived from gentamicin and imipenem against P. aeruginosa isolates. A hydrothermal method was used to synthesise amine-functionalised CDs (CDsGEN-NH2, CDsIMP-NH2) from gentamicin and imipenem precursors, respectively. Conjugation of imipenem to CDsGEN-NH2 (CDsGEN-IMP) and gentamicin to CDsIMP-NH2 (CDsIMP-GEN) was achieved using N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide. The synthesised CDs were analysed by HRTEM, zeta potential, UV-Vis, FTIR and fluorescence. The efficacy of photodynamic therapy (PDT) against P. aeruginosa ATCC27853 and two clinical P. aeruginosa isolates was evaluated using a combination of sub-minimum inhibitory concentrations (sub-MIC) and sub-lethal doses of UVA light (sDL) irradiation. The nanoscale size, electrical charge and photophysical properties of the synthesised CDs were confirmed by HRTEM, zeta potential, UV-Vis, FTIR and fluorescence techniques. Treatment with CDsGEN-NH2, CDsIMP-NH2 and CDsGEN-IMP at concentrations of 3 mg/mL (sub-MIC) and sDL irradiation for 10 s (3.12 J/cm) resulted in significantly reduced viability in P. aeruginosa ATCC27853 compared to the control (P ≤ 0.05), achieving viable cell reductions of 3.44, 3.11 and 2.65 log, respectively. Treatment with CDsIMP-GEN at a concentration of 125 µg/mL (sub-MIC) and sDL irradiation for 10 s (3.12 J/cm) also significantly reduced viability in P. aeruginosa ATCC27853 compared to the control (P ≤ 0.05), achieving a viable cell reduction of 3.75 log. These results demonstrate that CDs derived from imipenem and gentamicin can serve as effective antimicrobial agents in combination with UVA light irradiation for antimicrobial photodynamic therapy.