Small-sized Polydopamine Nanoparticles Loaded with Levofloxacin for Photothermal/Antibiotic Combined Bacterial Therapy

The dense cell wall of bacteria makes it difficult for large-sized nanoparticles to enter the interior of bacteria. The development of smaller-sized nanoparticles ( <= 30 nm) is the basis for constructing an ideal nanoparticle antibacterial platform. In this work, polydopamine ( PDA) nanoparticles with hydrodynamic diameter of 7-17 nm were synthesized by a top-down approach. After polyethylene glycol ( PEG) modification, these small-sized PDA-PEG nanoparticles could disperse well in phosphate buffered solution (PBS) for several months without precipitation. After further assembling the antibiotic levofloxacin (LVFX) with PDA-PEG, PDA-PEG-LVFX complex exhibited good photothermal effect and photothermal stability. Under laser irradiation at 808 nm, the bactericidal rates of PDA-PEG-LVFX nanoparticles (200 mu g/ mL ) against Staphylococcus aureus and Escherichia coli (5 x 106 CFU/ mL) were both 100% , exhibiting excellent photothermal-antibiotic combined antibacterial effect.