A comparative study on three unique galactosylated cationic liposomes with their steically stablized counterparts, in HepG2 cells.
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Date
2013
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Abstract
Receptor mediated endocytosis allows for the site specific delivery of exogenous
DNA via appropriate ligand-receptor interactions. Various ligands have been used to
target the asialoglycoprotein receptor (ASGP-R) present on the hepatocyte cell
membrane viz. asialofeutin, asialoorosomucoid, lac-BSA, asialolactoferrin, asialotransferrin,
asialo-ceruloplasmin and galactose. The high affinity that the receptor
displays for the galactose sugar moiety has led to the development of several new
galacto-lipids for the incorporation into liposomes intended for hepatocyte targeting.
In this study, three cholesteryl derivatives displaying galactose units linked to the
sterol skeleton by different spacer elements have been formulated into cationic
liposomes with and without polyethylene glycol (PEG) accessories. The three
galactosylated liposomal formulations were prepared using near equimolar amounts
of MSO9 (N,N-dimethylaminopropylamidosuccinyl-cholesterylformylhydrazide) and
DOPE (dioleoylphosphotidylethanolamine) together with the respective galactose
derivative (at 10 mole % w/w) viz. Cholesteryl-3β-N-(4-aminophenyl-β-Dgalactopyranosyl)
carbamate; Cholesteryl (1-β-D-galactopyranosyl-1,2,3 triazol-4-yl)
carbonate; and Cholesteryl-β-D-galactopyranoside. All liposomes displayed DNA
binding, nuclease protective capabilities to plasmid DNA, low cytotoxicity (cell
viability being within 60-101 %) and an increase in transfection activities, in the
human hepatocellular carcinoma cell line HepG2, which expresses the ASGP-R
abundantly. The results obtained correlate well with differences in the spacer element
in the 3 galactosylated cholesterol derivatives under study and the presence and
absence of 2 mole % DSPE-PEG₂₀₀₀ in the liposome formulations.
Overall, it was observed that the cationic liposome containing cholesteryl (1-β-Dgalactopyranosyl-
1,2,3 triazol-4-yl) carbonate (with and without PEGylated
accessories), which was synthesised chemically using “click chemistry”, afforded the
highest in vitro transfection activity, and may be optimised and studied further. The
highest levels of transfection activity, in vitro, were attributed to the increased length
of the spacer arm between the galactose moiety and the cholesteryl anchor of the targeting component. Two formulations were then subjected to in vivo studies, using
male Sprague Dawley rats which yielded little or no transgene expression.
Description
Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2013.
Keywords
Galactosyltransferases., Liposomes., Liposomes--Biotechnology., Theses--Biochemistry.