A Novel Peptide-Grafted Liposomal Delivery System Targeted to Macrophages

The interaction of chemotactic peptide (e.g., fMet-Leu-Phe)-grafted liposomes with macrophages is noted to be rapid and specific. At a grafted peptide concentration of 100 nmol, internalization of the peptide-grafted liposomes by the macrophages is found to reach equilibrium in 30 min. The peptide alone and the peptide-grafted empty liposomes are found to show moderate antileishmanial activity in vitro. Primaquine, which is known to generate O₂⁻ in phagocytic cells, showed leishmanicidal properties when it was tested in vitro against parasite-infected macrophages over a certain range of concentrations. It showed much better efficacy against experimental leishmaniasis when it was used in the fMet-Leu-Phe-grafted liposomal form in comparison with its efficacy when it was either in the free form or encapsulated in ungrafted liposomes. The conventional toxicity parameters (e.g., blood pathology and tissue histology-specific enzyme levels related to normal liver function) are found to be very close to normal when fMet-Leu-Phe-grafted liposomal primaquine is used. The biodegradabilities of both the drug and the delivery systems are also found to be very satisfactory. Thus, this delivery system may have possible applications for the treatment of leishmaniasis as well as other macrophage-associated disorders.