A decoloration/recoloration cycling-associated photo-stimulated fuel cell to assess potential health risks caused by TiO2 nanoparticles and tris(hydroxymethyl)aminomethane

Abstract

Nano-sized TiO2 and tris(hydroxymethyl)aminomethane (Tris) are widely used in diverse commercial products such as cosmetics, medicines and paints, therefore their possible exposure and consequent risk to humans and natural environments rouse public concerns. This paper evaluates potential health risks of UV-excited TiO2 and Tris buffer by constructing a decoloration/recoloration cycling-associated photo-stimulated fuel cell and using methylene blue (MB) as a color indicator through photo-oxidative damage of bovine serum albumin (BSA). Nano-TiO2 can bind BSA and MB to form TiO2@BSA-MB hybrids, revealed by TiO2-tuned binding constant, fluorescence quenching constant and MB-induced BSA configuration transition. The color retention efficiencies after decoloration/recoloration cycling and photocurrent responses from photo-stimulated fuel cells are able to monitor the photo-oxidative damage to BSA. Furthermore, Tris can be oxidized in photo-stimulated fuel cells in the absence of BSA whereas BSA has ability to depress the photocatalytic oxidation of Tris, which is found to increase the photo-oxidative damage of BSA caused by TiO2 and MB, therefore the simultaneous presence of TiO2, MB and Tris synergistically increases the photo-oxidative damage of BSA. The present results show new approaches for assessing the increased hazards to human health caused by photoradiation, nanomaterials and organic additives.