Choline-based ionic liquids enhance the dermal delivery of cyclosporine a for potential treatment of psoriasis.

Psoriasis is a prevalent chronic disease affecting 2-3% of the global population. Cyclosporine A (CyA) has been widely used with great promise in the treatment of moderate to severe psoriasis despite various side effects associated with its systemic administration. Topical administration of CyA circumvents systemic side effects; however, the poor water solubility and large molecular weight of CyA pose challenges for dermal delivery. In this study, choline-based ionic liquids (ILs) were used to enhance the dermal delivery of CyA for the potential treatment of psoriasis. All four ILs tested significantly improved the solubility of CyA, which was greater than that of the control group with dimethyl sulfoxide (DMSO) as a solubilizer (20%, w/w). The saturated solubility of CyA in two of the ILs, choline geranate ([Ch][Ge]) and choline ricinoleate ([Ch][Ra]), reached more than 90 mg/mL, and the solubilization capability of the ILs except [Ch][Ci] was resistant to water dilution. The negligible change in CyA content determined by high-performance liquid chromatography and the secondary structure detected by circular dichroism spectroscopy confirmed the stability of CyA in the ILs. At 4 h in the in vitro penetration test, the amount of CyA retained in the skin in the IL groups was slightly greater than that in the control group (20% DMSO). The water content of the ILs significantly affected their penetration ability. When the water content increased from 10 to 70%, the dermal delivery of CyA first increased, peaked at a water content of 30%, and then decreased. The dermal delivery ability of [Ch][Ge] and [Ch][Ra] with a water content of 70% was still comparable to that of 20% DMSO. Moreover, CyA-loaded ILs (0.5%, w/w) significantly relieved the symptoms of psoriasis in an imiquimod (IMQ)-induced mouse model, and the levels of inflammatory factors, including tumor necrosis factor α, interleukin 22 and interleukin 17, in the affected area were reduced by 71.7%, 75.6%, and 89.3%, respectively. The IL tested, choline sorbate ([Ch][So]), showed low cytotoxicity to human immortalized epidermal cells (HaCaT). After 7 days of consecutive application, [Ch][So] did not cause significant irritation. In conclusion, ILs demonstrate promising potential for the dermal delivery of CyA for the treatment of psoriasis.