Gold Nanorods Embedded in Polymeric Film for Killing Bacteria by Generating Reactive Oxygen Species with Light

For the first time, anisotropic gold nanorods (AuNRs) were embedded with a photosensitizer dye (crystal violet) in polyurethane (PU) matrix to create the effective antimicrobial film, capable of killing Gram-negative bacteria on its surface when exposed to white light. The dye, when activated with white light, interacts with the AuNRs to generate reactive oxygen species (ROS), which kill bacteria. With a proper control of the aspect ratio (2.1-2.4) and coating of the AuNRs, the film can be tuned to reduce the bacteria population of one to four orders of magnitude (1-log to 4-log) under 11 klux of light, for an exposure to light between 1 to 3 h. Particularly it could reduce 10⁴ cfu/cm² to the level of 1-5 cfu/cm² in 3 h of light exposure. This was a desired performance for use on hospital surfaces. In addition, the system showed antimicrobial effect only when exposed to light, which eliminated the concern for a cumulative toxic effect on subjects exposed to the material for a long period of time and limited the time given to the bacteria to develop resistance against the system. Furthermore, this process of sterilization could be carried out by a commercially available white light lamp, which when in use did not interrupt the normal routine operation of the environment.