Suppression of the photocatalytic activity of TiO 2 nanoparticles encapsulated by chitosan through a spray-drying method with potential for use in sunblocking applications

Solar exposure, in particular to UVA and UVB radiation, is a major carcinogen through direct DNA damage and the production of reactive oxygen species (ROS). Inorganic UV filters present in sunscreening agents, such as titanium dioxide (TiO2), are commonly employed for protection however, due to their photocatalytic nature, they have been shown to instigate the production of ROS when irradiated with UV radiation, which in turn can lead to the degradation of the sunscreening formulation and subsequent damage to the skin. In this work, chitosan/TiO2 nanocomposite particles were produced via a spray-drying method, in a single step, directly through aqueous solution for the purpose of reducing the photocatalytic activity of commercially available TiO2 nanoparticles. The photocatalytic activity of the nanocomposite materials were assessed using the organic dye, crystal violet, as the degradation target and irradiating in a UV reactor. It was found that the photoactivity of the chitosan encapsulated nanoparticles were greatly reduced compared to that of the pristine TiO2 nanoparticles, from 95% degradation after 120 min for pristine TiO2 to 39.5% for the chitosan/TiO2 spray dried particles, highlighting the potential for this simple coating process and chitosan material for application as an inactive protective coating for sunblocking applications.