Light-Activated Antibacterial Coating Battles Hospital-Acquired Infections

A new hard material coating with antibacterial properties has been shown to kill 99.9% of Escherichia coli bacteria when a regular white hospital light was shone on its surface to activate it.

Researchers at the University College London (UCL) Eastman Dental Institute (London, United Kingdom) developed the new veneer-like surface coating, which is made of titanium dioxide with added nitrogen; the addition of nitrogen to these coatings enables photons available in visible light to be utilized to activate the surface, decreasing in the number of bacteria surviving on the test surface. The coating was applied onto glass using a method called atmospheric pressure chemical vapor deposition (APCVD). The researchers are also experimenting with different materials such as plastic. For example, the coating could be applied to a plastic sheet that could be used to cover a computer keyboard on a hospital ward. The lights in the ward will keep the coating activated, which will in turn continue to kill any bacteria that may be transferred onto the keyboard from the hands of healthcare workers. The study was presented at the Society for General Microbiology meeting, held during March-April 2009 in Harrogate (United Kingdom).

"The activity of the coating will be assessed against a range of different bacteria such as MRSA and other organisms which are known to cause infections in hospitals. At present we only know that the coating is active against E. coli. However, E. coli is more difficult to kill than bacteria from the Staphylococcus group which includes MRSA, so the results to date are encouraging," said study presenter Zoie Aiken, M.D.

Titanium dioxide, particularly in the anatase form, is a photocatalyst under ultraviolet (UV) light. When spiked with nitrogen ions, or doped with metal oxide like tungsten trioxide, is also a photocatalyst under both visible and UV light. The strong oxidative potential of the positive holes oxidizes water to create hydroxyl radicals. It can also oxidize oxygen or organic materials directly. Titanium dioxide is thus added to paints, cements, windows, tiles, or other products for sterilizing, deodorizing, and anti-fouling properties, and is also used as a hydrolysis catalyst.

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UCL Eastman Dental Institute