Assembled gold nanorods for the photothermal killing of bacteria

Titanium and its alloys are widely used in many clinical applications, but implant-associated infection may lead to implant failure. Because of the increasing concern about antibiotic resistant pathogen, photothermal therapy (PTT) as a new treatment strategy has received considerable attention. In this work, gold nanorods (GNRs) photoexcited by the near-infrared (NIR) light were immobilized on Ti surface by electrostatic surface self-assembly technique. Field emission scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were used to explore the morphology and composition of the GNRs-modified surface. The photothermal temperature of the immobilized GNRs was measured by an infrared thermal imaging system in real time. In vitro study reveal that the prepared GNRs-modified surface exhibits antibacterial activity against four kinds of bacterial strains including both Gram-negative bacilli (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive cocci (Staphylococcus aureus and Staphylococcus epidermidis) under the irradiation of 808 nm laser. Besides, the antibacterial efficiency of the GNRs-modified surface could keep stable after multiple laser exposure. It should be noted that the GNRs-modified surface shows better antibacterial effect against Gram-negative bacilli compared to Gram-positive cocci. Moreover, the GNRs-modified surface has no obvious adverse effect to the osteoblast precursor cells under NIR irradiation. These data demonstrate that the GNRs-modified surface with negligible cytotoxicity and recyclable antibacterial effect provides a favorable model for the translation of photothermal therapy to the clinical application.