To investigate the enhancement mechanism of the oligo-chitosan (oligo-CS) on the transdermal delivery of drugs

the interactions of oligo-CS and D-glucosamine (DG) with the stratum corneum (SC) keratin were investigated in vitro with the lipid-extracted mouse SC and extracted keratin as models by EIS

SEM

DSC and FTIR methods.It was found that the DG solutions had no influence on the EIS value of the lipid-extracted mouse SCs.But oligo-CS solutions could reduce the EIS value of the lipid-extracted mouse SCs from the original 3.79×106 Ω . cm2 to 8.379×105 Ω . cm2.Moreover

SEM pictures showed that both oligo-CS solutions and DG solutions could destroy the keratin membranes.Furthermore

DSC determination revealed that the melting point of the α-helix micro-crystals in the keratin membranes was lowered from 201℃ to 190℃

189℃ and 165℃ after compositing with 1 wt% oligo-CS

5 wt% oligo-CS and 5 wt% DG

respectively.FTIR spectra exhibited that the amide II absorption peak of keratin shifted from 1523 cm-1 to 1520 and 1521 cm-1 after the treatment with 1 wt% oligoCS solution and 1 wt% DG solution

respectively.These results indicated that the interactions between the oligoCS and the SC keratin could destroy the tight junctions of the keratin cells and vary the keratin conformation from α-helix to β-sheet or random coil

resulting in a decreased skin barrier and an improved drug percutaneous permeation property.