The effects of ultraviolet (UV) radiation emitted by the sun are cumulative and can result in chemical changes such as the generation of reactive oxygen species (ROS), leading to the regular use of sunscreen. As an alternative, the use of antioxidants, such as quercetin, into sunscreen can control these effects and provide additional skin photoprotection. However, quercetin presents low stability and poor permeation, alternatively, the encapsulation in nanoparticles can improve the stability and skin permeation. Thus, this study aimed to develop photoprotective formulations containing nanoencapsulated quercetin, characterize the physical-mechanical and sensorial properties, and evaluate the influence of nanocarriers on sun protection factor (SPF) and the immediate clinical effects. Sunscreen formulations with or without antioxidants in a free form or loaded in nanostructured lipid carriers (NLCs) were developed. After the stability, rheological behavior, texture profile, and in vivo SPF (sun protector factor) evaluation, sixty female participants, aged between 20 and 35 years, were enclosed to evaluate the sensorial properties and immediate clinical effects of the formulation in the skin hydration using biophysical and skin imaging techniques. The correlation of rheological behavior, texture profile, and sensory properties enabled the correct choice of formulation ingredients. In addition, the use of NLCs with quercetin significantly improved the SPF in vivo of the developed photoprotective formulation, without increasing the amount of UV filters. Finally, the association of NLCs in the photoprotective formulation showed synergistic effects in the SPF and an improvement in the skin barrier function and hydration.
Keywords: biophysical techniques; mechanical properties; nanostructured lipid carriers; rheological behavior; sunscreen.