Elucidation of Cell Killing Mechanism by Comparative Analysis of Photoreactions on Different Types of Bacteria

Abstract

The mechanism of biocidal action of nano titania on Escherichia coli and Staphylococcus aureus has been evaluated by various biochemical techniques like lipid peroxidation, hydrolysis of orthonitrophenol β-D-galactopyranoside, estimation of protein-amino acid and bacterial nucleic acids leakage into solution, in addition to morphology studies by electron microscopy (TEM and SEM) and K(+) ion leakage by inductively coupled plasma optical emission spectrometry. The active anatase phase of nano titania has been synthesized by sol-gel and pulverization techniques to obtain particle sizes averaging around 11 nm. The nano semiconductor with a bandgap of 3.2 eV responds well to the UV source to liberate reactive oxygen species (ROS). Gram negative bacteria easily succumb to the ROS at a faster rate than gram-positive bacteria with an observable difference in the mode of attack. The use of analytical techniques revealed the release of peroxidized lipid (26 nmol mL(-1) ) and protein content (370 μg mL(-1)) with a K(+) ion concentration of 22 000 ppb on complete destruction of E. coli.

The short-term toxic effects of TiO2 nanoparticles toward bacteria through viability, cellular respiration, and lipid peroxidation

“…On the other hand, some studies have shown Gram(+) bacteria to be more easily inactivated than Gram(−) bacteria (Matsunaga et al 1985;Valduga et al 1993). The experimental results of this work and others indicate that Gram(+) and Gram(−) cells may undergo different mechanisms of photocatalytic inactivation (Foster et al 2011;Swetha et al 2012). Therefore, more research is required to determine the sensitivity of bacteria to NP suspensions under different environmental conditions.…”

“…The polyunsaturated phospholipid component of the cell membrane is oxidized by the ROS generated by TiO 2 NPs and forms MDA. It has been very well documented in the literature that MDA increases with the extent of membrane oxidation in the presence of light (Maness et al 1999;Nadtochenkoa et al 2005;Sökmen et al 2001;Swetha et al 2012). However, it is also interesting to note that the presence of TiO 2 (34.2 nm) also brought about lipid peroxidation in the dark (Erdem et al 2007).…”

Photoactive Titania Float for Disinfection of Water; Evaluation of Cell Damage by Bioanalytical Techniques

“…The protein concentration in the filtrate was measured by the method of Lowry et al . with bovine serum albumin as a standard at a particular value of λ max = 753 nm . The concentration of released DNA was quantified by diphenylamine method where the released DNA reacts with diphenylamine to give a blue color and the absorbance was measured at 595 nm.…”

“…Titania and its doped analogues were investigated in powder form for bactericidal activity with respect to both gram‐positive and gram‐negative bacteria . But the suspended powders seemed to pose a problem of separation before the usage of disinfected water, limiting it to practical applications.…”

Atomic force microscopic study of nanoscale interaction between N719 dye and CdSe quantum dot in hybrid solar cells and their enhanced open circuit potential

“…Synthesis was done by similar method as reported in our earlier paper (Swetha et al, 2012). About 100 ml of TiCl 4 was added drop wise to a liter of double distilled water.…”