Photodynamic Inactivation of Bacteria by a Monosubstituted 3‐[4‐(Sodium sulfonate)phenoxy] Zinc Phthalocyanine/Nitrogen‐Doped Graphene Quantum Dot Nanoconjugate

Abstract

The worldwide escalation of antimicrobial resistance poses an urgent threat to global health, prompting the pursuit of alternative treatments. In this study, we report the synthesis and characterization of an innovative photosensitizer nanoconjugate comprising monosubstituted 3‐[4‐(sodium sulfonate)phenoxy] zinc phthalocyanine (ZnSTPc) and nitrogen‐doped graphene quantum dots (NGQDs) for antimicrobial photodynamic therapy (aPDT). Electron paramagnetic resonance measurements showed that NGQDs‐ZnSTPc generated significantly higher levels of singlet oxygen and hydroxyl radicals than either component alone. This enhancement was associated with FRET, with a calculated efficiency of 37.19%. In vitro photodynamic antibacterial assays demonstrated that NGQDs‐ZnSTPc reduced Escherichia coli survival to 0.09% at 200 µg/mL, while no viable Staphylococcus aureus were detected at 50 µg/mL within the of assay under 680 nm light irradiation (200 mW/cm 2 , 20 min). These results underscore the potential of NGQDs‐ZnSTPc as an effective antimicrobial photosensitizer, offering advantages of lower irradiation intensity and shorter treatment time compared with existing systems.