Facile synthesis of ε-poly-L-lysine-conjugated ZnO@PDA as photothermal antibacterial agents for synergistic bacteria killing and biofilm eradication

Nanomaterial-based antimicrobial strategies have emerged as powerful tools to combat microbial resistance, avoiding side effects of misusing antibiotics. In this work, the zinc oxide-based nanohybrid (designated as ZnO@PDA-ε-PL) as broad-spectrum antibacterial agents were fabricated in a facile two-step process. To be specific, ZnO was coated with near-infrared (NIR)-photoresponsive polydopamine (PDA), and then coupled with the antimicrobial peptide (AMP) (ε-poly-L-lysine, ε-PL). The as-prepared ZnO@PDA-ε-PL can effectively contact and capture bacteria, and then exhibit an excellent photothermal effect, i.e., the temperature rises rapidly to 53.2 °C (100 μg/ml) under 808 nm NIR light irradiation for 10 min. The synergistic effect of ε-PL, ZnO and photothermal agent PDA contributes to the excellent antibacterial efficiency of ZnO@PDA-ε-PL (<100 μg/ml) with 808 nm irradiation, that is, 99.70% and 100.00% against Gram-negative bacteria (Escherichia coli, E. coli) and Gram-positive bacteria (Staphyloccocus aureus, S. aureus), respectively. Further experiments indicated the ZnO@PDA-ε-PL ultimately lead to bacterial death by disrupting cell integrity, leaking of intracellular components (e.g., nucleic acids). Moreover, ZnO@PDA-ε-PL can effectively remove 70.84% of S. aureus biofilms. Overall, NIR-responsive ZnO@PDA-ε-PL has great potential in the field of infection treatment.