A host-rotaxane derivatized with carboxylic acids efficiently delivers a highly cationic fluoresceinated peptide

A cleft-[2]rotaxane (CR2+2−) was derivatized with carboxylic acids to enhance the intracellular delivery of a highly cationic or anionic pentapeptide. CR2+2− delivers the fluorescein (Fl) tagged peptide Fl-KKALR to a greater amount than Fl-QEAVD, and at a higher concentration, a greater amount than Fl-AVWAL. The level of delivery is largely temperature and ATP independent, suggesting that the Fl-peptide•CR2+2− complexes pass through the cellular membrane without requiring active cell-mediated processes. This study shows that selective delivery of peptides is possible by using a suitably derivatized host-rotaxane as the transporter.