Liposome−Cell Interactions in Vitro:  Effect of Liposome Surface Charge on the Binding and Endocytosis of Conventional and Sterically Stabilized Liposomes

Abstract

The cellular uptake of liposomes is generally believed to be mediated by adsorption of liposomes onto the cell surface and subsequent endocytosis. This report examines the effect of liposome surface charge on liposomal binding and endocytosis in two different cell lines: a human ovarian carcinoma cell line (HeLa) and a murine derived mononuclear macrophage cell line (J774). The large unilamellar liposomes were composed of 1, 2-dioleolyl-sn-glycero-3-phosphatidylcholine with and without the addition of either a positively charged lipid, 1, 2-dioleoyl-3-dimethylammonium propanediol (DODAP), or a negatively charged lipid, 1,2-dioleolyl-sn-glycero-3-phosphatidylserine. In some experiments 5 mol % of the anionic PEG2000-PE or a neutral PEG lipid of the same molecular weight was added. HeLa cells were found to endocytose positively charged liposomes to a greater extent than either neutral or negatively charged liposomes. This preference was not lipid-specific since inclusion of a cationic cyanine dye, DiIC18(3), to impart positive charge in place of DODAP resulted in a similar extent of endocytosis. In contrast the extent of liposome interaction with J774 cells was greater for both cationic and anionic liposomes than for neutral liposomes. The greater uptake of positively charged liposomes by HeLa cells was also observed with sterically stabilized liposomes (PEG liposomes). Although the overall amount of endocytosis for all the PEG liposomes examined was attenuated relative to conventional liposomes, the extent of endocytosis was greatest for positively charged PEG liposomes, whereas negatively charged PEG2000-PE liposomes were hardly endocytosed by the HeLa cells. Incorporation of a neutral PEG lipid into liposomes permits the independent variation of liposome steric and electrostatic effects in a manner that may allow interactions with cells of the reticuloendothelial system to be minimized, yet permit strong interactions between liposomes and proliferating cells.

The effect of particle design on cellular internalization pathways

“…Even under extended incubation times, PRINT nanoparticles exhibited no cytotoxicity. Numerous studies have shown that surface charge has a significant impact on cellular internalization of a variety of nanocarriers (23). Dependence of surface charge on cellular internalization of PRINT nanoparticles was investigated by using rapidly internalized high-aspect-ratio cylindrical nanoparticles (d ϭ 150 nm, h ϭ 450 nm).…”

Stabilized Porous Phospholipid Nanoshells

“…HeLa cells readily internalize nanoparticles of similar size to those used in this work, including 120 nm phospholipid vesicles, 50 nm gold nanoparticles and 18 nm silica nanoparticles. [35][36][37] Furthermore, EGFP fluorescence was stable within the cell in excess of two hours, suggesting that the PPN architecture protects the encapsulated components from intracellular proteases which may degrade the protein. Combined with PPN permeability and stability studies, these results strongly suggest the utility of polymerized PPNs for delivering enzymes and large molecular weight reporters to the intracellular environment and may represent a new paradigm for cellular analysis as well as diagnosis and treatment of disease.…”

Biodistribution and Feasibility of Non-Viral IGF-I Gene Transfers in Thermally Injured Skin

“…For gene expression to occur, DNA plasmids enter the cell and its cell nucleus. Although there are three possible pathways of cell entry, endocytosis is likely the principal mechanism for transfection (Caplen et al, 1995;Lasic, 1998;Miller et al, 1998;Noguchi et al, 1998). After cellular uptake, the released cDNA is taken up by the nucleus (Felgner et al, 1995).…”