Binding of cationic cell-permeable peptides to plastic and glass

Cell-penetrating peptides derived from hydrophilic regions of the homeoprotein Antennapedia (Antp) or the transcription-regulating factor Tat have been used to transport several peptide and oligonucleotide cargoes into the interior of cells. Such vector peptides penetrate cells, in part, because they contain multiple lysine and arginine residues. Using radiolabeled peptide cargoes covalently linked to Antp- or Tat-related vectors, or to D-Arg heptamers, we found that a significant amount of the label remained tightly bound to plastic and glass surfaces. Binding of the labeled conjugates was due entirely to the cationic vector moieties. Under certain conditions, such non-specific binding could be mistaken for cellular penetration.