Low photocatalytic CeO2/TiO2 nanocomposite particles with high UV attenuation and reduced ROS generation for application in sunscreen products.

K. (2018). Suppression of the photocatalytic activity of TiO2 nanoparticles encapsulated by chitosan through a spray-drying method with potential for use in sunblocking applications. Powder Technology, 329 252-259. AbstractSolar 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 (TiO 2 ), 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/TiO 2 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 TiO 2 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 TiO 2 nanoparticles, from 95% degradation after 120 min for pristine TiO 2 to 39.5% for the chitosan/TiO 2 spray dried particles, highlighting the potential for this simple coating process and chitosan material for application as an inactive protective coating for sunblocking applications. Disciplines Engineering | Physical Sciences and Mathematics Publication DetailsMorlando, A., Sencadas, V., Cardillo, D. & Konstantinov, K. (2018). Suppression of the photocatalytic activity of TiO2 nanoparticles encapsulated by chitosan through a spray-drying method with potential for use in sunblocking applications. Powder Technology, 329 252-259. AbstractSolar 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 (TiO 2 ), 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/TiO 2 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 TiO 2 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 TiO 2 nanoparticles, from 95% degr...

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A deficiency in the human antioxidant system to scavenge free radicals results in mounting oxidative stress, causing various pathological conditions including immune system constraints. To support an underperforming antioxidant system and regulate homeostatic function, efficient and biocompatible reactive oxygen species (ROS) scavengers may be employed. At present, metal oxide-based antioxidants nanoparticles are of fundamental interest because of their smart surface property tailoring. A spray precipitation method was employed in this work to develop a strained and defect rich lanthanum oxide (La 2 O 3 ) nanostructure. A contraction in d-spacing and distortion in planes and vacancies were observed in the nanostructure, causing microstrain as verified by the William-Hall uniform deformation model (UDM). Photocatalytic activity was evaluated against commercial La 2 O 3 and Evonik Aeroxide TiO 2 P25 via dye degradation experiments. A 30% degradation reduction confirmed the ability of the nanostructure to scavenge free radicals generated by P25 upon ultraviolet (UV) irradiation. Compared to the commercial La 2 O 3 , the nanostructured La 2 O 3 showed an increase in UV absorption (200−400) nm due to a decrease in the optical band gap. A positive surface charge of the nanoparticles was observed from zeta potential measurements, suggesting sufficient colloidal stability. In vitro toxicity studies toward the nonmalignant human keratinocyte cell line (HaCaT) over a 24 h treatment period with the La 2 O 3 nanoparticles exhibited no toxicity in comparison with the control and ZnO nanoparticles. The antioxidant properties of the nanoparticles were investigated by a dichlorofluorescein (DCF)-based assay which revealed a decrease in intracellular ROS in comparison with Nacetylcysteine (NAC) and H 2 O 2 . In addition, confocal microscopy imaging showed the internalization of the nanoparticles and subsequent DCF intensity change between the treated and untreated cells, as supported by flow cytometry analysis. Our findings suggest that defect-rich La 2 O 3 nanoparticles could be used effectively as active inorganic UV filter and fluorescent contrast agent owing to their biocompatible antioxidant properties.