Fe3O4–Au–polydopamine hybrid microcapsules with photothermal–photodynamic synergistic anti-bacterial performance

Abstract

Infectious diseases associated with drug-resistant bacteria increasingly threaten public health. Effective antibacterial nanoplatforms are of special importance for treating bacterial infections. In this work, a novel magnetic Fe₃O₄–Au–PDA hybrid microcapsule with both photothermal (PTT) and photodynamic (PDT) anti-bacterial functions was developed. First, the Fe₃O₄@Au/PDA core/shell microspheres with hollow nature were obtained by a simple in situ redox–oxidize polymerization method. Then, they were etched in acid to improve the hollow interior and porous shell. Finally, the tetracarboxyzinc phthalocyanine (ZnPc) was used as the photosensitizer to be loaded into the above Fe₃O₄–Au–PDA hybrid microcapsule. Owing to the dual-mode photothermal Au–PDA hybrid shell and the ZnPc photosensitizer, the final Fe₃O₄–Au–PDA/ZnPc hybrid microcapsule serves as a wonderful photothermal/photodynamic (PTT/PDT) synergistic therapy agent. The experimental results show that the Fe₃O₄–Au–PDA/ZnPc microcapsule possesses excellent photothermal sterilization effect (808 nm laser irradiation) against Escherichia coli, and the experimental results further demonstrate good photodynamic behavior under Xenon lamp irradiation. The product exhibits much higher antibacterial performance by combining the PTT/PDT treatment, which demonstrates that this work provides a novel dual-mode phototheranostic nano-agent for an effective treatment of bacterial infections.