Syntheses and cellular studies of water soluble porphyrin-peptide conjugates

Conjugates of meso-tetraphenylporphyrin to the cell targeted NLS SV40 and HIV-I Tat 48-60 peptide sequences were synthesized on solid-phase using optimized conjugation protocols. Polar groups were introduced at the periphery of the prophyrin macrocycle, and their effect on the in vitro biological performance of the conjugates was evaluated. In vitro biological studies using the new porphyrin conjugates in human HEp2 cells showed that the conjugates bearing the HIV-I Tat sequence were the most efficiently delivered within cells. The cellular uptake was also dependent on the nature of the substituents at the periphery of the porphyrin macrocycle. On the other hand, the conjugates containing the NLS SV40 peptide sequence and/or hydrophobic groups at the porphyrin periphery were the most phototoxic. The subcellular distribution of the conjugates depended significantly on the nature of the peptide sequence and the overall molecule charge. The conjugates delivered into the more sensitive ER were more phototoxic to the HEp2 cells than those that localized mainly in the lysosomes