Overcoming electrically induced artifacts in penetration studies with fluorescent tracers

The use of model molecules in transdermal transport studies reveals transport behavior while providing an economical setup by detection of readily measured quantities such as fluorescence, radioactivity or absorbance of low-cost substances. Water soluble fluorescent tracers such as calcein have been repeatedly used as model molecules in transdermal transport studies. However, if electrically enhanced calcein transport across the human skin barrier is measured, artifacts due to interaction between calcein and electrode byproducts influence the result. Here, we describe an experimental setup which avoids known artifacts and makes calcein or other fluorescent tracers a suitable model for transdermal transport studies.