Nanostructured lipid carriers for percutaneous administration of alkaloids isolated from Aconitum sinomontanum

BACKGROUND Lipid-based nanosystems have great potential for transdermal drug delivery. In this study, nanostructured lipid carriers (NLCs) for short-acting alkaloids lappacontine (LA) and ranaconitine (RAN) isolated from Aconitum sinomontanum (AAS) at 69.47 and 9.16% (w/w) yields, respectively, were prepared to enhance percutaneous permeation. Optimized NLC formulations were evaluated using uniform design experiments. Microstructure and in vitro/in vivo transdermal delivery characteristics of AAS-loaded NLCs and solid lipid nanoparticles (SLNs) were compared. Cellular uptake of fluorescence-labeled nanoparticles was probed using laser scanning confocal microscopy and fluorescence-activated cell sorting. Nanoparticle integrity during transdermal delivery and effects on the skin surface were also investigated. RESULTS NLC formulations were less cytotoxic than the AAS solution in HaCaT and CCC-ESF cells. Moreover, coumarin-6-labeled NLCs showed biocompatibility with HaCaT and CCC-ESF cells, and their cellular uptake was strongly affected by cholesterol and lipid rafts. Significantly greater cumulative amounts of NLC-associated LA and RAN than SLN-associated alkaloids penetrated the rat skin in vitro. In vivo microdialysis showed higher area under the concentration-time curve (AUC)0-t for AAS-NLC-associated LA and RAN than for AAS-SLN-associated alkaloids. CONCLUSIONS NLC formulations could be good transdermal systems for increasing biocompatibility and decreasing cytotoxicity of AAS. AAS-NLCs showed higher percutaneous permeation than the other preparations. These findings suggest that NLCs could be promising transdermal delivery vehicles for AAS.