Monoacyl-phospatidylcholine nanostructured lipid carriers: Influence of lipid and surfactant content on in vitro skin permeation of flufenamic acid and fluconazole

Monoacyl-phosphatidylcholine (MAPL) is a skin-friendly phospholipid emulsifier that has successfully been employed for development of microemulsions. Its potential for stabilising particulate lipid drug carriers has not been explored so far. Thus, the aim of the present study was the development of MAPL-based nanostructured lipid carriers (NLC) as dermal drug delivery system with optimised physical stability. To this end, extensive comparative studies were performed and the role of crucial formulation parameters such as total lipid or surfactant content was investigated. Both blank placebo NLC and drug-loaded systems were developed using flufenamic acid and fluconazole as model drugs of different polarity. The resulting systems were characterised using photon correlation spectroscopy, laser Doppler electrophoresis, rheological measurements and cryo transmission electron microscopy. In vitro skin diffusion studies revealed that interestingly, both a low surfactant content and a low total lipid content led to increased skin permeation of flufenamic acid in vitro. According to its different polarity, a different trend was observed for fluconazole where higher surfactant contents in combination with different total lipid contents yielded the highest skin permeation. Satisfying long-term stability of the NLC formulations with optimised physical parameters was observed for a period of 30 weeks.

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