Design and evaluation of photothermal and chemical multimodal antibacterial agents based on ZIF-8

Bacterial infections pose a significant threat to global public health, and the presence of bacterial biofilms complicates the treatment of these infections. Therefore, the development of materials with both antibacterial and antibiofilm properties is crucial. In this study, we designed a composite material that combines chemical and photothermal antibacterial functions using a zeolitic imidazolate framework (ZIF-8) and protocatechuic acid (PCA). PCA-ZIF was synthesized by immersing ZIF-8 in a PCA solution, followed by surface encapsulation with polydopamine (PDA) through dopamine polymerization to enhance its photothermal therapy potential. This process yielded PCA-ZIF@PDA, which can generate localized hyperthermia and gradually release PCA to achieve multimodal antibacterial activity. The structure of the composite was characterized using XRD, FTIR, SEM, and BET, and its photothermal performance under 808 nm laser irradiation, drug release profile, and in vitro antibacterial efficacy were also evaluated. The results indicated that the immersion of PCA did not alter the crystal structure of ZIF-8, however, the polydopamine (PDA) coating significantly reduced its crystallinity. The PCA loading capacities were measured at 253.7 mg⋅g −1 for PCA-ZIF and 209.2 mg⋅g −1 for PCA-ZIF@PDA. The photothermal conversion efficiency of the 1 mg⋅mL −1 sample under 808 nm irradiation was found to be 61.4 %. Under near-infrared irradiation and acidic conditions (pH 5.0), the cumulative drug release from PCA-ZIF@PDA reached 91 % after 12 h. Antibacterial experiments demonstrated that PCA-ZIF@PDA effectively killed E. coli and S. aureus , inhibited their growth, and significantly prevented biofilm formation.