A variety of antibacterial strategies have been proposed for implant surgery, but the in vivo cytotoxicity remains a big concern. Hence, there is an urgent need to develop antibacterial materials with better cytocompatibility. 

Titania (TiO₂) is promising in enhancing implant biocompatibility. However, it loses antibacterial function under dark conditions, for instance, in human body.

Recently, researchers from the Shenzhen Institutes of Advanced Technology (SIAT) of the Chinese Academy of Sciences and Changzhou University found that plasma sprayed titania coatings doped with a certain amount of graphene nanosheets (GNS) showed antibacterial activity under darkness, due to a mechanism associated with electron transfer. 

The addition of GNS greatly improved the electric conductivity of the TiO₂ coating. This design facilitated the transport of extraneous electrons in bacteria, thus interfering with their normal respiratory electron transport chain.

Consequently, the electron gathering and enrichment at the schottky-like GNS-TiO₂ interface might lead to ROS generation, resulting in a remarkable antibacterial activity under darkness. 

Besides, in vitro cell culture experiments confirmed that GNS-TiO₂ composite coatings possessed comparable cytocompatibility with pure TiO₂ coatings.  

"The findings of this work will possibly diversify the application of graphene-based nanomaterials in the biomedical field, and provide new ideas for the design of biocompatible and effective antibacterial implant coatings," said Prof. WANG Guocheng from SIAT. 

The study was published in Carbon. It was supported by the National Key R&D Program of China, the National Natural Science Foundation of China, Shenzhen Science and Technology Research Funding, and Guangdong Provincial Science and Technology Project. 

Possible antibacterial mechanism of the GNS-TiO₂  coating (Image by SIAT)