Hydrogels containing spray-dried avobenzone and resveratrol-loaded nanocapsules using titanium dioxide and microalgae as drying adjuvants: An innovative formulation for photoprotection

Photoprotective substances are needed to minimize the harmful effects of UV radiation on the skin. In this context, the objective of this work was to develop and characterize a hydrogel containing spray-dried avobenzone and resveratrol loaded nanocapsules using titanium dioxide and microalgae as drying adjuvants. The nanocapsules, previously developed and characterized, were dried using the spray drying technique with the aid of titanium dioxide (3% w/v) and/or a mixture of it (2.7% w/v) with the microalgae of the species Scenedesmus ecornis as excipients (0.3% w/v). The powders showed good yields (67-70%), with low moisture content (<1.5%) and average particle size in the micrometer range (>30 µm). The drying process of spray-dried powders did not significantly affect the content of avobenzone and resveratrol (above 85% for both), although the morphological description indicates the presence of micro-agglomerates. Subsequently, the powders were incorporated into hydrophilic gels prepared with sodium acrylates copolymer and lecithin. Then, the hydrogel containing spray-dried avobenzone and resveratrol loaded nanocapsules was produced and characterized using titanium dioxide and microalgae (HG-NCA+R+TiM) as a drying adjuvant. The formulation was evaluated for irritability by HET-CAM, permeation/penetration of avobenzone, washability profile and in vitro efficacy. The hydrogel presented a pH value of 7.52, drug content of 1.24% for avobenzone (w/w) and 0.04% for resveratrol (w/w), and a non-Newtonian pseudoplastic rheological behavior. The free avobenzone from a hydrogel and from HG-NCA+R+TiM did not permeate the skin layers. The evaluation by HET-CAM did not detect irritating reactions of the formulation. The structure of HG-NCA+R+TiM allowed a greater resistance to the washing flow indicating good adhesive capacity on the skin surface in comparison to the free hydrogel. The in vitro efficacy test showed that HG-NCA+R+TiM absorbed and spreaded the UV light with maximum wavelengths in the erythematous range (305-328 nm). In conclusion, these spray-dried powders are promising formulations to be incorporated into photoprotective hydrogels intended for cutaneous administration.