Enhanced skin photoprotection integrating a spray-dried hesperetin nanocapsules semisolid formulation: Development of the formulation and clinical trial study.

This study aimed to develop a cosmetic formulation containing dried hesperetin nanocapsules using titanium dioxide as a drying excipient (spray-dried NC-HT-TiO2) for photoprotection. Nanoformulation was evaluated and characterized for cytotoxicity, stability, adhesion, skin penetration and permeation, irritability (HET-CAM), skin toxicity, in vitro photoprotective effects, SPF values, and pilot clinical study in volunteers. The hesperetin nanocapsules showed an average particle size of 205.70 nm, low polydispersity index, negative zeta potential, hesperetin loading of 0.48 mg.mL-1, and encapsulation efficiency of 97.20 %. After spray-drying, the microparticles had a size of 36.30 μm, moisture content of 1.32 %, active content of 4.60 mg.g-1, and percentage of hesperetin recovered of 97 %. Unlike free hesperetin, the formulation did not affect the viability of keratinocytes. Likewise, it did not cause irritability and reveal skin toxicity in the HET-CAM model and in Tenebrio molitor larvae, respectively. The composition presented suitable adhesion to the skin (60 % of drug retained in the stratum corneum), and maintained stability in pH, active content, and appearance for 90 days of storage under different conditions. In the in vitro photoprotection study, spray-dried NC-HT-TiO2 exhibited a high photoprotective capacity (88 %) by protecting resveratrol from UVA-UVB light photodegradation compared to controls (2.5-50 %). The formulation also had an SPF value of 12.71 ± 0.13, while the cream-gel base of 1.58 ± 0.34. Furthermore, the composition presented a capacity similar to that of an SPF 30 sunscreen in protecting the skin of volunteers exposed to UV light from erythema, transepidermal water loss, and increased melanin index in the skin. Finally, spray-dried NC-HT-TiO2 exhibits promise for protecting the skin against solar radiation because of its stability, skin adhesion, skin penetration, safety, and photoprotective efficacy.