The photosensitizer system based on cationic COF carrier with the loading tetraminoporphyrin and its combined antibacterial effect

Abstract

Antibiotic resistance induced by antibiotic abuse is considered as one of the most serious public health problems. Antibacterial photodynamic therapy (APDT) using an efficient photosensitizer has been gaining increasing attention in recent years owing to its high efficacy and lack of drug resistance. Herein, we reported a photosensitizer system composed of tetra-aminophenyl porphyrin (TAPP) loaded in a guanidinium-based ionic covalent framework (COF_TGTp) via π–π interactions to form TAPP/COF_TGTp. The aim was to use it for APDT, which will not only solve the problems with TAPP as a photosensitizer, wherein it easily aggregates in aqueous solution and is ineffective against Gram-negative bacteria, but can combine the antibacterial activity of the cationic COF_TGTp with the APDT induced by TAPP to achieve optimal antibacterial effects on both Gram-positive and Gram-negative bacteria. After TAPP loading in COF_TGTp, the stability of TAPP/COF_TGTp in aqueous solution was enhanced compared with TAPP, and the drug-loading efficiency could reach 27%. Under white-light irradiation, TAPP/COF_TGTp can be activated to catalyze oxygen conversion into reactive oxygen species (ROS) including singlet oxygen (¹O₂); this will annihilate bacteria via the full use of the positive charge of cationic COF_TGTp, which closes the distance between the bacteria and ROS. In addition, MTT and hemolysis experiments showed that TAPP/COF_TGTp was almost noncytotoxic and did not cause hemolysis. Most remarkably, the minimum inhibitory concentrations (MICs) of TAPP/COF_TGTp for E. coli and S. aureus were 100 μg mL⁻¹ and 50 μg mL⁻¹, respectively. As a result, TAPP/COF_TGTp is expected to be an antibacterial material and have promise for substituting traditional antibiotics to solve antibiotic resistance and the emergence of superbacteria.