Investigating phosphatidylcholine and phosphoethanolamine phospholipids in conventional and novel cationic nanoliposomes for interactions with chronic myeloid leukemia cells in vitro

Background: Lipid Nanoparticles (LNPs) have been established as excellent vehicles for drug/nucleotide delivery for Chronic Myeloid Leukemia (CML). The optimization of lipid ratios of cationic and helper lipids, such as phosphatidylcholine (PC) and phosphoethanolamine (PE)- based lipids, governs the selectivity of LNPs. Furthermore, the incorporation of LE (lipid extracts) derived from target cell membranes has been used to develop CLENs (cell membrane lipid-extracted nanoliposomes) for superior targeting. However, the behavior of PE- and PC-based lipids in the presence of LE is not well understood. In this study, we investigate the cellular interactions of LNPs consisting of PE or PC phospholipids employed in different combinations of cationic lipids and/or lipid extract ingredients using a model CML (K562-GFP) cell line. Methods: The K562-GFP human CML cell line (CCL-243-GFP) was cultured in RPMI-1640 medium supplemented with 10% fetal bovine serum (FBS). LNPs were prepared using the thin film hydration method and characterized for size and zeta potential. Phase I of the study compared the cellular uptake of LNPs, substituting four cationic lipids (DOTAP, EPC, DOTMA, DODMA) at varying concentrations (0-50 mol%) with the helper lipid DOPC. Phase II involved comparing the PC versus PE helper lipid at a fixed cationic lipid concentration determined in Phase I. Phase III of the study aims to investigate the cellular uptake of LNPs after the inclusion of LE at various concentrations by target and non-target cell lines. Results: We identified the cellular uptake to be about 250% higher for LNPs containing 25 mol% of DOTAP or EPC compared to the control (DOPC 100 mol%) from Phase I. Phase II revealed that LNPs with helper lipid DOPC performed significantly better at all time points (0 to 120 min) with an increase in cellular uptake compared to helper lipid DOPE. In phase III, the inclusion of LE derived from the target cell in the cationic LNPs led to a selective uptake by the target cell line and decreased uptake by the non-target cell lines. Conclusion: Results to date revealed that the cellular uptake of LNPs depends largely on the optimum ratio of the cationic lipid to the helper lipid type employed in the development of the nanoparticles, and that inclusion of LE leads to superior targeting.