Toxicity Associated with the Photo Catalytic and Photo Stable Forms of Titanium Dioxide Nanoparticles Used in Sunscreen lotion

Abstract

Abbreviations: IARC, international agency for research on cancer; UV, ultraviolet; QD, quantum dot; ROS, reactive oxygen species; PBS, phosphate buffered saline; CB, conduction band IntroductionThe properties of materials change as their size approaches the nano particle scale, which is generally considered to be that with at least one dimension of 100nm or less. The toxicity of nanoparticles has been linked to such characteristics as elemental composition, charge, shape, Crystallinity, surface area, solubility and surface chemistry/ derivatization. [1][2][3][4][5][6] Understanding the nano particle-cell interaction is thought to be critical for the safe development of nano materials. 7 It seems unlikely that the potential toxicity of nanoparticles and the underlying mechanisms can be predicted or explained by any single unifying concept.This review is focused on Titania (TiO 2 ) for which there is substantial interest in the chemical, biological, and industrial worlds because of its fascinating and useful physicochemical properties. Currently, information describing the relative health and environmental risks associated with nano-TiO 2 is severely lacking. Only recently, critical questions regarding the potential human health and environmental impact of nano-TiO 2 have been raised. [8][9][10][11] TiO 2 particles have long been considered to pose little risk to respiratory health because they are both chemically and thermally stable. 12 However, TiO 2 is classified as a Group 2B carcinogen by the International Agency for Research on Cancer (IARC) based on the findings of lung tumor induction in female rats. 13,14 Nano-TiO 2 is attractive for use in a large number of applications based on its unique optical and photo catalytic properties, tunable band gap, thermal stability, chemical resistance and hardness.15Because of the relatively large band-gap, the particles absorb the higher-energy (shorter wavelength) ultraviolet radiation making it a useful constituent in sunscreen products. TiO 2 photo catalysis is widely used in the fields of wastewater treatment, 16 sterilization, 17 self-cleaning, 18 hydrogen evolution, 19 and photoelectron chemical conversion. 20 Normally, TiO 2 can only be excited with ultraviolet (UV) light because of its wide band gap, 21 although this is considered a drawback when photo catalytic conversion is desired under visible light. The crystalline structure is the major factor determining the band gap, but secondary factors include the particle size and the presence of defects (physical or chemical). 22,23 A large surface-tomass ratio of the nanoparticles helps to promote catalytic reactions, and increases their ability to absorb and carry other compounds. Their surface reactivity originates from quantum phenomena that can make nano-TiO 2 seemingly unpredictable. 24Engineered nano-TiO 2 is designed to impart specific characteristics that vary according to their use. Aside from unique nanoscale properties (size, Crystallinity, reactivity, and thermodynamics), nanoTiO 2 may be funct...