Variables affecting the antibacterial properties of nano and pigmentary titania particles in suspension

The antibacterial activity of photoactivated nano and pigmentary titania particles in suspension was evaluated using Escherichia coli as the target organism. The antibacterial activity of nanotitanium particles was determined more by their intrinsic ability to generate radicals than to particle size. Indeed there was an inverse relationship between particle size and activity. The antibacterial activity of the particles was affected by multiple experimental parameters. The reliability and variability of the results were affected by the physiological status of the bacterial cells, the initial cell concentration, and the set up of the irradiation system and were also improved if the cell–particle mixture was stirred during irradiation. The development of appropriate in vitro testing methods is essential in the determination of antimicrobial effectiveness of these particles and this is examined here coupled with the use of the microwave spectroscopic method for determining the photoactivity of the pigments in terms of carrier generation.