Preparation and evaluation of cellular uptake of liposomes modified with cell penetrating lipo peptides

Abstract

Background: Liposomes are spherical vesicles composed of one or more lipid bilayer (s) entrapping an aqueous compartment. Their similarity to cell membranes makes them useful as a carrier. Despite the high promise of liposomes as drug carriers the cellular uptake is limited. By attaching specific targeting ligands to the liposomal surface to specifically interact with certain cell surface receptors the cellular uptake of liposomes can be enhanced. Among all these ligands Cell Penetrating Peptides (CPPs) have attracted the attention of ours. CPPs are short peptides that facilitate cellular uptake of various molecular equipment. Aim: We aimed to prepare CPP modified liposomes and evaluate their cellular uptake. Methods: Four sequences of CPPs with 8 amino acids in each one, were synthesized by solid phase peptide synthesis (SPPS) method. Succinyl-cholesterol was prepared and the structures formation was confirmed by the means of NMR and FTIR. Succinyl-cholesterol was attached to peptide sequences, then CPP modified liposomes were prepared and their size distribution was assessed by Zetasizer and cellular uptake of liposomes was studied by florescence microscopy and flow cytometry. Results: FTIR and 1H-NMR spectrums confirmed that all desired compounds were formed. Fluorescence microscope and flow cytometry graphs indicated an increase in cellular uptake corresponded to the high relative abundance of positively charged amino acids such as lysine or arginine on the liposome surface. Conclusion: Some specific synthesized CPPs as modifiers of surface of liposome increased cellular uptake massively as 15.28 times, plain liposomes’ while enhancement of some other sequences’ was only by 0.53 times- signifying the sequence’s minimal effect on the cellular uptake of liposomes modified with.