Development of a protocol to study the bactericidal activity of metal anatase (TiO2)

Metal anatase (TiO ) is an industrially important compound, currently used in a variety of 2 applications as a white pigment. Anatase has also been shown to kill bacteria in the presence of blue light. This property has been exploited in the purification of water. However, the basis of cell killing has not been confirmed and remains under investigation. To study the proposed model of killing by reactive oxygen species, a suitable protocol must be designed. Sample volume, culture concentration, method of anatase plate sterilization, and light intensity are important variables that influence the degree of killing. Previous experiments focused on small volume sizes, however in this study larger sample volumes were used to investigate the feasibility of large scale sterilization procedures. Due to difficulties in development of a functional protocol, killing in large volume samples could not be assessed, yet remains a future pursuit. Killing in a 150µl bubble was enhanced when anatase plates were sterilized by boiling in water compared to sterilization with acetone. Killing was also enhanced when light intensity was increased. Although these modifications resulted in enhanced cell killing, it was still substantially less than previously reported. As the activity of these anatase plates was greater in experiments conducted five years ago, the effect of plate age and storage on the long-term activity of anatase should be investigated.