This study aimed to develop sunscreen emulsion from natural sunscreening agents, titanium dioxide and Aloe vera gel extract that have good sun protection efficacy. The effects of formulation variables i.e., particle size and amount of titanium dioxide, amount of Aloe vera gel extract (spray dried powder) and combination of sunscreening agents (titanium dioxide and Aloe vera gel extract) on physical properties and sun protection efficacy (e.g., SPF, UVA/UVB ratio, critical wavelength) of sunscreen products were evaluated. The results showed that the smaller particle size of titanium dioxide improved the sun protection efficacy and increased the UVB absorption edge of the products. SPF of the formulations could be ranked as Nanofine TiO2 (particle size 25–30 nm) > Kingruti T-01 TiO2 (particle size 200 nm) > Pigment TiO2 (particle size < 45,000 nm) and UVA/UVB ratio and critical wavelength of the formulations could be arranged in order as follows: Nanofine TiO2 < Kingruti T-01 TiO2 < Pigment TiO2. Increasing amount of titanium dioxide from 5 to 15 %w/w increased significantly viscosity and SPF of formulations. Aloe vera gel extract itself did not significantly affect SPF, however, combination of Aloe vera gel extract and titanium dioxide seemed to have synergistic effect on sun protection efficacy and decreased viscosity of the formulation. According to the results, the good sunscreen formulation consisted of 15 %w/w Nanofine TiO2, 5 %w/w Aloe vera gel spray dried powder in emulsion base because it was broad spectrum sunscreen and showed high SPF (27.53±1.92), high UVA/UVB ratio with critical wavelength higher than 370 nm.
Effects of the physicochemical properties of titanium dioxide nanoparticles, commonly used as sun protection agents, on microvascular endothelial cells
