Synergistic effects of chemical enhancers on skin permeability: a case study of sodium lauroylsarcosinate and sorbitan monolaurate.

Certain mixtures of chemicals are known to synergistically enhance skin permeability to drugs. Here, we report on the transport enhancing properties of mixtures of an anionic surfactant, sodium lauroylsarcosinate (NLS) and a non-ionic surfactant, sorbitan monolaurate (S20) in 1:1 phosphate buffered saline (PBS):ethanol (EtOH) solvent. Effect of 44 different compositions of NLS:S20 on skin constituents was probed by Fourier transform-infrared (FT-IR) spectroscopy while behavior of surfactant molecules in the solvent system was probed by FT-IR and NMR spectroscopy. No aggregation of NLS or S20 alone was observed in 1:1 PBS:EtOH at all concentrations studied (0-2%, w/v). However, mixtures of NLS and S20 resulted in micelle-like aggregates at certain specific compositions. Interestingly, compositions with increased aggregation showed resemblance to those that exhibited highest skin permeabilization.