Sodium dodecyl sulfate improved stability and transdermal delivery of salidroside-encapsulated niosomes via effects on zeta potential.

Niosomes are novel carriers that show superior transdermal permeation enhancement but require the addition of charged stabilizers. In this study, niosomes were prepared using Span 40, cholesterol, and sodium dodecyl sulfate (SDS) as stabilizers for transdermal delivery of salidroside. At concentrations of 0.05-0.40% (w/v), SDS significantly increased the zeta potential of the nanovesicles from -18.5 ± 3.2 to -157.0 ± 5.2 mV and improved the stability of the niosomal formulations. Niosomes prepared with a Span 40:cholesterol molar ratio of 4:3 and 0.1% SDS showed good stability and the highest transdermal drug delivery among all tested formulations, with 2.75-fold higher transdermal flux of 20.26 ± 1.05 μg/(cm2·h) than that of aqueous salidroside solution. However, excess SDS increased the negative charge on the vesicle surface and hence repulsion with skin cells, leading to reduced drug entrapment efficiency and cellular uptake of niosomes. Although SDS in the niosomes dose-dependently increased the in vitro cytotoxicity of the formulation in skin cells, HaCaT and CCC-ESF-1 cell viability was ≥ 80% for formulations containing ≤0.1% SDS. No significant irritation was observed on rat skin with once-a-day topical application of the niosomal formulations for 7 consecutive days. Thus, SDS is a promising stabilizer for nanomedicines, including niosomes, for transdermal administration.