Surface-catalysed disinfection of thick Pseudomonas aeruginosa biofilms.

Transition metal catalysts were incorporated into polymers which formed the surface for bacterial attachment and biofilm formation in a constant depth film fermenter (100 microns thickness), flow chamber (about 30 microns thickness) and in batch culture (< 30 microns thickness). The catalysts drive the breakdown of persulphates to reactive oxygen species. When Pseudomonas aeruginosa biofilms were exposed to dilute solutions of potassium monopersulphate (20 micrograms ml-1-1 mg ml-1), significant enhancement of killing was notable for catalyst-containing surfaces over that of controls. The degree of enhancement was greatest for thin films, but was nevertheless significant for the 100 microns thick biofilms. Fluorescence probes and viability staining, in conjunction with laser confocal microscopy, showed that reactive species were generated at the biofilm-substratum interface and killed the biofilm from the inside. Reaction-diffusion limitation now concentrates the active species within the biofilm rather than protecting it, and a diffusion bump is established whereby further treatment agent is drawn to the substratum enabling relatively thick biofilms to be disinfected.