Gold Nanoparticles Prevent Infection on Orthopedic Implants

Due to a phenomenon known as localized surface plasmon resonance (a collective oscillations of electrons), an Au@TiO2 system could effectively kill bacteria in darkness by affecting respiratory electrons of the bacterial membrane, making them steadily lose electrons by transferring them first to the Au nanoparticles and then to TiO2, until they die.

To do so, they prepared close-packed TiO2 nanotube arrays on a metallic Ti surface by electro-chemical anodization. Then, using magnetron sputtering, they deposited Au nanoparticles to coat the Ti surfaces. The researchers then allowed Staphylococcus aureus and Escherichia coli to grow separately on the arrays. They found that both organisms were highly unsuccessful, exhibiting profuse membrane damage and cell leakage. The study describing the technology was published on June 30, 2014, in the journal Applied Physics Letters.

“Implant-associated infections have become a stubborn issue that often causes surgery failure. Designing implants that can kill bacteria while supporting bone growth is an efficient way to enhance in vivo osteointegration,” concluded senior author Prof. Xuanyong Liu, PhD. “This work provides insights for the better understanding and designing of noble metal nanoparticles-based plasmonic heterostructures for antibacterial application.”

TiO2 is able to kill bacteria itself due to its properties as a photocatalyst; when the metal is exposed to light, it becomes energetically excited by absorbing photons. This generates electron-hole pairs, turning Ti into a potent electron acceptor that can destabilize cellular membrane processes by usurping their electron transport chain's terminal acceptor. The dark conditions inside the human body, however, limit the bacteria-killing efficacy of TiO2. Gold nanoparticles, though, can continue to act as antibacterial terminal electron acceptors under darkness, due to localized surface plasmon resonance at the interface between conductors and dielectrics, such as between gold and TiO2.

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Shanghai Institute of Ceramics