Combining photothermal gold nanorods and antibiotics for treatment of implant-associated infections

Abstract

Implant-associated infections commonly require repeated treatment and high dosages of antibiotics. Being able to effectively treat implant-associated infections is therefore critical for the future of medical implants as well as being able to decrease the usage of antibiotics. This thesis therefore considers a possible alternative to decrease the usage of antibiotics and to more effectively treat implant-associated infections by combining photothermal gold nanorods and antibiotics to achieve a synergistic effect. A procedure has been developed to enable evaluation of the antimicrobial activity and synergistic effect of the combination of photothermal gold nanorods and antibiotics by In-Vitro studies. Before performing the In-Vitro studies were gold nanorods synthesised with dimensions enabling emission of photothermal heat when exposed to near-infrared (NIR) light, heat which can be used for photothermal elimination of bacteria. The gold nanorods were thereafter immobilised on glass substrates by electrostatic interaction, mimicking a gold nanorod-functionalised implant surface. The gold nanorod-functionalised substrates were thereafter implemented in the In- Vitro studies to evaluate the antimicrobial activity of the gold nanorods exposed to NIR-light. An antimicrobial effect could be achieved when the substrates were exposed to NIR-light covered with a thin liquid film meanwhile no antimicrobial effect could be achieved when the substrates were exposed to NIR-light while immersed in liquid. The antimicrobial activity of vancomycin was also evaluated by minimum inhibitory concentration (MIC) determinations where the MIC for planktonic bacteria and bacteria cultivated on gold nanorod-functionalised substrates were determined. The antimicrobial effect was thereafter evaluated for the combination of gold nanorods exposed to NIR-light and vancomycin. No synergistic effect could be achieved for the parameters considered. No antimicrobial activity nor synergistic effect could therefore be achieved when the gold nanorod-functionalised substrates were irradiated immersed in liquid, with or without antibiotics. The results implicate that more studies are required and that the interaction between the gold nanorods and the bacteria needs to be studied in more detail.