Targeted Disinfection of E. coli via Bioconjugation to Photoreactive TiO₂

The selective control of pathogenic bacteria is an ongoing challenge. A strategy is proposed that combines targeted binding of the bacterium, using antibodies, with their photoactivated oxidative destruction. Photoactive colloidal TiO₂ was first derivatized with E. coli antibodies (EA-TiO₂). When mixtures of the organisms E. coli and Pseudomonas putida (P. putida) were exposed to modified EA-TiO₂, the particles preferentially selected E. coli for surface binding. Two consequences arose from surface bioconjugation: bacteria were found to flocculate upon mixing at appropriate ratios of EA-TiO₂/E. coli, and EA-TiO₂-bound E. coli underwent cell death after exposure to UV light. In the former case, flocculation of the bacteria was optimal at ∼50 EA-TiO₂ particles per E. coli. Selective flocculation provides an alternative strategy for pathogen removal. With respect to UV disinfection, as few as 26 EA-TiO₂ particles per E. coli gave a 10 000-fold decrease in viable bacteria. Thus, it is possible to selectively target and kill one type of bacteria in a mixture of pathogens. The results give support to the proposal that photocatalytic TiO₂ most effectively delivers an oxidizing agent when the titania is bound to the bacterial surface