Precise tuning of porphyrin self-assembly and photo-activated antimicrobial activity via metal ion coordination

Bacterial drug resistance has emerged as a significant threat to global human health, prompting the need for alternative antimicrobial strategies. Photodynamic therapy (PDT) has garnered widespread attention as a promising antimicrobial approach that circumvents the issue of bacterial resistance. Porphyrin is a class of photosensitizers with promising potential. In this study, we utilized the strategy of precise tuning of self-assembly of porphyrin through the coordination of metal ions to achieve the efficient and selective photo-activated antimicrobial. Typically, the selected porphyrin (TPPS₄) serves as the foundation for an investigation into the role of metal ions (Mⁿ⁺) as regulatory agents. The coordination of various metal ions (Bi³⁺, Ca²⁺, Zn²⁺, and Mn²⁺), with TPPS₄ results in differentiated molecular stacking, which in turn affects the morphology of the self-assembled structures and their capacity to generate reactive oxygen species (ROS), ultimately leading to varied antimicrobial activities. The study found that the antibacterial capability of the system is positively correlated with its ability to generate reactive oxygen species (TPPS₄-Bi ≈ TPPS₄-Ca > TPPS₄ >TPPS₄-Zn >TPPS₄-Mn). This work paves the way for the development of novel photodynamic antimicrobial agents that are both highly potent and minimally toxic, offering a significant advancement in the field of antimicrobial therapy.