Formulation and biological evaluation of a bacterial nanocellulose-based nanoemulsion hydrogel loaded with Persea americana Mill. seed extract: An anti-aging assessment

Avocado ( Persea americana Mill.) seed is an underutilized by-product rich in catechins and fatty acids, with potential anti-aging properties. However, the utilization of avocado seed in topical formulations is limited by its poor solubility, physicochemical instability, and minimal skin penetration. Therefore, this study aimed to develop and evaluate a bacterial nanocellulose (BNC)-based nanoemulsion hydrogel incorporating avocado seed extract as a topical anti-aging delivery system. Nanoemulsions were prepared using avocado seed oil, Cremophor® RH40, and PEG 400, followed by incorporation into a BNC matrix to obtain a hydrogel-like formulation. Physicochemical characteristics were evaluated by globule size, polydispersity index (PDI), transmittance, pH, viscosity, morphology (TEM), FT-IR profile, and freeze-thaw stability. Skin permeation study was conducted using Franz diffusion cells, while anti-aging activities were assessed using the pinch test, skin hydration, and collagen density assessment in UVB-induced photoaging rat model.The optimized nanoemulsion exhibited a globule size of 20.3 ± 0.10 nm, PDI of 0.109 ± 0.029, transmittance of 99.62 ± 0.27%, and pH of 4.92 ± 0.01 with 1:6:3 ratio of oil, surfactant, and co-surfactant subsequently. The formulation was stable in globule size, PDI, or pH after three freeze–thaw cycles. Incorporation of avocado seed extract up to 5% did not adversely affect nanoemulsion characteristics. The cumulative permeation of BNC-based nanoemulsion was significantly higher than BNC-based conventional emulsion, reaching 198.28 ± 0.54 µg/cm 2 after 120 min compared with 121.35 ± 0.54 µg/cm 2 . In vivo studies showed that the formulation significantly improved skin elasticity, hydration, and collagen density while reducing UVB-induced wrinkle formation (p < 0.05). In conclusion, the developed BNC-based nanoemulsion hydrogel successfully enhanced the delivery of avocado seed extract and provides a stable and effective platform for topical delivery of natural bioactive compound in anti-aging cosmetic applications.