Temperature influences the postelectroporation permeability state of the skin

The influence of temperature on the electrical conductance and transport of macromolecules across porcine epidermis during and after electroporation were studied. The passive diffusion of fluorescein isothiocyanate labeled dextran (molecular weight 10 kDa, FD10K), across the epidermis did not differ much at temperatures below 37 degrees C, but became significantly higher above 40 degrees C. The resistance drop during pulse application was less sensitive to temperature within the temperature range (10-50 degrees C) of this study. The kinetics of decrease in postpulse conductance of the electroporated epidermis was fit to a monoexponential function. The rate of decrease in postpulse conductance was significantly less and FD10K transport was markedly high at temperature over 40 degrees C relative to those observed at temperatures less than 37 degrees C. This jump in transport cannot be explained by electrophoresis induced by the pulse, or by the increased diffusion kinesis of the molecules. The enhanced transport is most likely due to the prolonged postpulse permeable state of the skin. Electroporation at mild hyperthermia temperatures resulted in delivering much higher quantities of macromolecules.