Cell penetrating peptides (CPPs) are promising tools for transducing presynthesized therapeutic molecules which possess low membrane permeability. The poor efficiency of cellular uptake and unexpected cellular localization are still the main obstacles to the development of drug delivery by using CPPs. In this study, we investigated the effect of a penetration enhancer, dimethylsulfoxide (DMSO), on the penetrating efficiency of a synthetic TAT peptide or the TAT fusion protein. FITC-labeled TAT and TAT-GFP were added to 10% DMSO or 100 microM chloroquine pretreated cells, fluorescence uptake into culturing cells was observed using fluorescence microscopy, FACS or quantitatively analyzed by a fluorescence spectrum. 10% DMSO treatment markedly increased internalization of TAT into cells and appeared in a well-distributed pattern throughout the cytosol and nucleus without membrane perforating or detectable cytotoxicity, the enhancement effect by 10% DMSO was reduced by endocytosis inhibitors including ammonium chloride and sodium azide. 10% DMSO also enhanced TAT-Apoptin induced apoptosis of carcinoma cells. These findings implicated that DMSO can be a novel delivery enhancer appropriate for CPP penetration.
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