Trypsin as a novel potential absorption enhancer for improving the transdermal delivery of macromolecules

Abstract

AbstractObjectivesThe aim was to assess the effect of trypsin on the transdermal delivery of macromolecules by applying its specific biochemical properties to the stratum corneum of the skin.MethodsFluorescein isothiocyanate (FITC)-labelled dextrans (FDs), with molecular weights of 4 to 250 kDa, and FITC-insulin were used as model macromolecules and a model polypeptide, and the in-vitro transdermal permeation experiments, with or without trypsin (0.1–2.5%), were carried out using rat skin and cultured human epidermis. The mechanism for the enhancement of trypsin was also studied using fluorescence and conventional light microscopy.Key findingsTrypsin significantly increased the transdermal permeability of all FDs through the rat skin (2.0- to 10.0-fold). It also markedly enhanced the permeation of FD4 through three-dimensional cultured human epidermis (3.1-fold), which was used to evaluate the transport pathways other than the transfollicular route. Furthermore, the permeation flux of FITC-insulin was increased by 10.0-fold with trypsin pretreatment (from 0.02 ± 0.00 to 0.20 ± 0.07 μg/cm2 per h). Mechanistic studies indicated that trypsin affects both the intercellular pathway and the hair follicular route, and may alter stratum corneum protein structures, thereby affecting skin barrier properties.ConclusionsThis study suggests that trypsin could be effective as a biochemical enhancer for the transdermal delivery of macromolecules including peptide and protein drugs.