Topical nanostructured lipid carrier gel of quercetin and resveratrol: Formulation, optimization, in vitro and ex vivo study for the treatment of skin cancer

[Display omitted] •Optimization and preparation of QCT & RSV loaded NLCs for the treatment of skin cancer.•Synergistic actions over the use of single drugs in skin cancer treatment through targeting of multiple molecular pathways.•Improved drug accumulation in dermal layers.•Improved cytotoxic and anti-metastatic effects. The objective of this investigation was to develop dual drug-loaded nanostructured lipid carrier (NLC) gel of quercetin and resveratrol to enhance their disposition in dermal and epidermal layers. The optimization of the lipidic phase, i.e., liquid lipid and solid lipid was done on the basis of the solubility of quercetin & resveratrol in lipids in the preformulation stage. NLC formulation was optimized by central composite rotatable design (CCRD). The NLC formulation contained lipid binary mixture (1.0% w/w) and Cremophor RH40 (5% w/v) as a surfactant and had a particle size of 191 nm ± 5.20, polydispersity index (PDI) of 0.33 ± 0.01, zeta potential (ZP) of −10.00 mV ± 0.30 and entrapment efficiency (EE) of 92.85 ± 0.25% (quercetin), 89.05 ± 0.18% (resveratrol) respectively. The flux and permeability coefficient of quercetin and resveratrol from NLC gel were found to be 14.09 µg/cm2/h, 3.70 µg/cm2/h and 7.21 × 10−2 cm/h, 4.69 × 10−2 cm/h respectively. Dermatokinetic studies revealed that there was a significant increase in the CSkin max and AUC0–8 h in skin treated with NLC gel as compared to skin treated with conventional gel, which was prepared using carbopol 934 (1.5% w/w). Further, all claims of dermatokinetic studies were proved by confocal microscopic (CLMS) studies, which revealed that the disposition of combinatorial NLC gel was higher (~3 folds) as compared to the conventional gel. Furthermore, skin treated with NLC gel and untreated skin were analysed by FTIR and DSC spectra to understand the permeation dynamics of NLC gel. The cytotoxic effect of combinatorial NLC gel and the conventional gel assessed in human epidermoid carcinoma (A431) cell line by MTT assay, revealed that IC50 of NLC gel and the conventional gel was 86.50 µM and 123.64 µM respectively. Thus, these results disclosed that NLC gel could be used as a potential carrier for the delivery of quercetin & resveratrol into deeper layers of the skin and can serve as a promising formulation for treatment of skin cancer.