Hydrophobically modified inulin based nanoemulsions for enhanced stability and transdermal delivery of retinyl propionate

Nanovesicles are attractive for cosmetics application owing to their enhanced stability and transdermal delivery of active ingredients. Retinyl propionate (RP) is a promising anti-aging ingredient but it is usually unstable in formulations. In this work, we developed RP-loaded nanoemulsions using polymeric hydrophobically modified inulin (HMI), small-molecular polysorbate 20 (PS-20) as the main emusifiers and positively-charged behen-trimonium chloride (BC) as a zeta-potential adjuster. Systematically optimizing the composition of the three emulsifiers led to small droplet size (<100 nm) and high physical stability of the nanoemulsions. Importantly, RP loaded in the nanoemulsions exhibited a high retention rate exceeding 80% after storage at 50 celcius for 30 days. The superior RP stabilization and anti-coalescence property of the nanoemulsion could be attributed to the densely-packed, sterically-hindered and highly-charged interfacical layers composed of multiple emulsifiers at the oil-water interface. In addition, in vitro skin permeation experiments in a Franz diffusion cell suggested that the as-prepared nanoemulsions exhibited highly enhanced transdermal delivery of RP into the epidermis and dermis compared to the conventional emulsions. Therefore, the present work provides a feasible approach for more effective application of retinol esters in cosmetic formulations.