The aim of this work was to evaluate the low molecular weight chitosans (LMWCs) as enhancers of transdermal administration of baicalin, an useful drug for the treatment of atopic dermatitis, viral hepatitis, and HIV infection. Permeation experiments were performed in vitro through mouse skin by using Franz cells. Improved baicalin skin penetration was obtained with the addition of LMWCs or D-glucosamine (beta-D-GlcNH(2)) to the donor solutions. Chitosan molecular weight, degree of deacetylation, pH of donor baicalin solutions, and enhancer concentration all affected LMWC enhancement effects. Significant enhancement was observed at pH 7.0 or 7.5 for CS80-1000, and the enhancement factor (EF) in the co-delivery method was calculated as 11.7 or 15.9, respectively. Simultaneously, beta-D-GlcNH(2) showed greatest enhancement at pH 7.0 with an EF of 11. Moreover, there was an optimal concentration range (0.5-1% by weight for CS80-1000 and 1.0-1.5% for beta-D-GlcNH(2)) to enhance baicalin transdermal delivery. It was concluded that the effective fractions for the enhancement of LMWCs were beta-D-GlcNH(2) oligomers, and the repeated number of beta-D-GlcNH(2) was suggested to be in the range 2-6. Enhancement mechanism of LMWCs was also discussed and suggested to be relative to the interactions of LMWC with both baicalin and the lipid of stratum corneum.
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