Shape-dependent bactericidal activity of TiO2 for the killing of Gram-negative bacteria Agrohacterium tumefuciens under UV torch irradiation

摘要

This paper demonstrated the relative bactericidal activity of photoirradiated (6W-UV Torch, A>340 run and ratensity=0.64 mW/cm2) P25-TiO_2 nanoparticles, nanorods, and nanotubes for the killing of Gram-negative bacterium Agrobacterium tumefaciens LBA4404 for the first time. TiO_2 nanorod (anatase) with length of 70-100 nm and diam?eter of 10-12 nm, and TiO_2 nanotube with length of 90-110 nm and diameter of 9-11 nm were prepared from P-25 Degussa TiO_2 (size, 30-50 nm) by hydrothermal method and compared their biocidal activity both in aqueous slurry and thin films. The mode of bacterial cell decomposition was analyzed through transmission electron microscopy (TEM), Fourier transform-infrared (FT-IR), and K+ ion leakage. The antimicrobial activity of photoirradiated TiO_2 of different shapes was found to be in the order P25-TiO_2> nanorod> nanotube which is reverse to their specific surface area as 54< 79<176 m~2 g~(-1), evidencing that the highest activity of P25-TiO_2 nanoparticles is not due to surface area as their crystal siructure and surface morphology are entirely different. TiO_2 iliin films always exhibited less photoactivity as compared to i's aqueous suspension under similar conditions of cell viabil?ity test. The changes in the bacterial surface morphology by JV-irradiated P25-TiO_2 nanoparticles was examined by TEM, oxidative degradation of cell components such as pro?teins, carbohydrates, phospholipids, nucleic acids by FT-IR spectral analysis, and K~+ ion leakage (2.5 ppm as compared to 0.4 ppm for control culture) as a measure of loss in cell membrane permeability.