Mechanical and baicalin delivery properties of adhesive matrices for iontophoretic flexible electrodes.

The aim of this work was to evaluate the feasibility and efficacy of flexible adhesive electrodes (FAEs) prepared with adhesive matrices for iontophoretic delivery of baicalin, a drug used for the treatment of atopic dermatitis, viral hepatitis and HIV. Single-layer adhesive matrices (SLAMs) and double-layer adhesive matrices (DLAMs) were prepared from carbomer 940, sodium alginate and polyvinyl alcohol with appropriate mechanical and high baicalin release properties. During the direct-current (DC) iontophoresis with SLAM FAEs, electrochemical reaction caused a clear decrease of pH value at the interface IF(+,FCL) and an increase of pH value at the interface IF(-,FCL). An additional pH-controlling layer in DLAMs could adjust the pH value of interfaces. Thus, deterioration of baicalin stability and the competitive delivery of hydroxyl ions produced with baicalin anions would be avoided during iontophoresis. Iontophoretic flux of baicalin from a DLAM FAE cathode increased proportionally to the time from the onset and affected by the current density and the frequency of pulsed DC. Increasing the applied current or the frequency could enhance the skin permeation flux of baicalin. Moreover, the baicalin skin permeation flux could be further improved from 0.22 microg/cm(2) per h in iontophoresis alone to 0.43 microg/cm(2) per h in the combined approach of iontophoresis and Azone.