Sorbitan Monolaurate-Containing Liposomes Enhance Skin Cancer Cell Cytotoxicity and in Association with Microneedling Increase the Skin Penetration of 5-Fluorouracil

Squamous cell carcinoma (SCC) represents 20% of cases of non-melanoma skin cancer, and the most common treatment is the removal of the tumor, which can leave large scars. 5-Fluorouracil (5FU) is a drug used in the treatment of SCC, but it is highly hydrophilic, resulting in poor skin penetration in topical treatment. Some strategies can be used to increase the cutaneous penetration of the drug, such as the combination of liposomes containing penetration enhancers, for instance, surfactants, associated with the use of microneedling. Thus, the present work addresses the development of liposomes with penetration enhancers, such as sorbtitan monolaurate, span 20, for topical application of 5-FU and associated or not with the use of microneedling for skin delivery. Liposomes were developed using the lipid film hydration, resulting in particle size, polydispersity index, zeta potential, and 5-FU encapsulation efficiency of 88.08 nm, 0.169, -12.3 mV, and 50.20%, respectively. The presence of span 20 in liposomes potentiated the in vitro release of 5-FU. MTT assay was employed for cytotoxicity evaluation and the IC₅₀ values were 0.62, 30.52, and 24.65 μM for liposomes with and without span 20 and 5-FU solution, respectively after 72-h treatment. Flow cytometry and confocal microscopy analysis evidenced high cell uptake for the formulations. In skin penetration studies, a higher concentration of 5-FU was observed in the epidermis + dermis, corresponding to 1997.71, 1842.20, and 2585.49 ng/cm² in the passive penetration and 3214.07, 2342.84, and 5018.05 ng/cm² after pretreatment with microneedles, for solution, liposome without and with span 20, respectively. Therefore, herein, we developed a nanoformulation for 5-FU delivery, with suitable physicochemical characteristics, potent skin cancer cytotoxicity, and cellular uptake. Span 20-based liposomes increased the skin penetration of 5-FU in association of microneedling. Altogether, the results shown herein evidenced the potential of the liposome containing span 20 for topical delivery of 5-FU.