Synthesis, penetrability and intracellular targeting of fluorescein-tagged peptoids and peptide–peptoid hybrids

The search for novel, generally applicable and highly efficient delivery tools is a major activity in the biotechnology arena. Using highly optimized microwave based solid-phase chemistry a series of fluorescein-labelled cationic peptoid conjugates were synthesized within 24 h and cellular uptake into HeLa, L929 and K562 cells examined via flow cytometry. As expected, analysis revealed that longer oligomers achieved greater cellular penetration (7e (9 mer) > 7d (7 mer) > 7c (5 mer) > 7b (3 mer) > 7a (1 mer)) with the nonamer 7e proving to be a remarkable vehicle for all the cell lines, showing excellent penetrability into K562 and L929 cells and extraordinary cell delivery into HeLa cells. Confocal microscopy showed that the hybrid peptoid-nuclear localizing sequence (PKKKRKV from the simian virus 40 large T antigen) resulted in very high levels of nuclei delivery after 3 h, opening up a range of applications such as nuclei staining of living cells with non-DNA-intercalating fluorescent probes.

A cell-penetrating peptoid nonamer conjugated to the SV40 nuclear localization signal (NLS) permitted rapid and specific intracellular trafficking and targeting to the cell nucleus, facilitating nuclei staining of live cells with a non-DNA-intercalating fluorescent probe.Figure optionsDownload as PowerPoint slide