Effects of electric polarization of indium tin oxide (ITO) and polypyrrole on biofilm formation.

The influence of electric polarization on primary adhesion and on biofilm formation was investigated. As substrata, indium tin oxide (ITO) and polypyrrole coatings were used because of their electric conductivity. The materials were polarized from -600 mV to +600 mV, switching every 60 seconds. Control was non-polarized substrata. Primary adhesion under this regime was not strongly influenced, however, the morphology of the primary biofilm was obviously different from that of the control. Biofilm formation of the natural population of non-chlorinated drinking water, supplemented with nutrient in low concentration, was determined over 164 hours. While the biofilm on the control surface developed to a thickness of about 100 microm, on the pulsed polarized surface it reproducibly developed only to a very thin biofilm. Faster switching of the polarization (10 second) had no further influence. If the polarization routine was reduced to only twice a day (one hour), no influence on biofilm development was observed. These results indicate that fluctuating polarization at a rate of once per minute inhibits the physiological processes during biofilm formation during one week. Investigations are in process to determine further details of this effect in order to employ it for inhibition of biofouling.