Browsing by Author "Sewbalas, Alisha."

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Novel cationic lipoplexes : characterization in cell culture in vitro and in vivo.
(2010) Sewbalas, Alisha.; Ariatti, Mario.; Singh, Moganavelli.; Arbuthnot, Patrick Brian.
Amongst the more promising non-viral DNA vehicles are liposomes, with those derived from cationic lipids showing significant potential, despite moderate transfection levels in vivo. This study has investigated the effect of liposome-anchored ionophore crown ethers on lipoplex-mediated gene transfer in vitro and in vivo. Several liposomes were constructed to include the cytofectin 3β[N(N’,N’-dimethylaminopropane)-carbamoyl] cholesterol (Chol-T), the co-lipid dioleoylphosphatidylethanolamine (DOPE), and 5% (mole/mole) of the cholesteryl crown ethers RUI-128 (aza-18-crown-6) or RUI-129 (aza-15-crown-5). Liposome size and lamellarity were established by transmission electron microscopy. All liposome preparations were shown to bind, condense and protect DNA avidly in the respective band shift, ethidium displacement and nuclease protection assays. Lipoplex targeting to hepatocytes may be achieved via the asialoglycoprotein receptor (ASGP-R), which is abundantly expressed on the human hepatoblastoma cell line HepG2. Therefore six additional liposomes were formulated to include 5% (mole/mole) of the cholesteryl galactosyl RUI-90 (Gal) and cholesteryl glucosyl RUI-92 (Glu) ligands. Their hepatotropic gene delivery was examined in the HepG2 cell line using the pCMV-luc plasmid. Transfection studies in the human embryonic kidney cell line HEK293 (ASGP-R-negative) revealed an increase in transgene activity in lipoplexes displaying the RUI-129 cholesteryl derivative. No ionophore-mediated enhancement of transfection activity was observed in HepG2 cells although Chol-T:DOPE, Chol-T:DOPE:RUI-128 and Chol-T:DOPE:RUI-129 liposomes achieved very high transfection levels, exceeding those of their hepatocyte targeted counterparts. Liposome-anchored crown ethers have been shown to potentiate in vitro transfection activity of lipoplexes in the HEK293 cell line. The novel cholesteryl glycosyl derivatives were, however, unable to enhance the targeted entry of lipoplexes into HepG2 cells. The three most effective preparations from in vitro studies were taken forward for in vivo assessment in NMRI mice at the University of the Witwatersrand Molecular Medicine and Haematology unit. Three groups of mice were employed for the evaluation of Chol-T:DOPE, Chol-T:DOPE:RUI-129 and Chol-T:DOPE:RUI-129-Gal lipoplexes with the Psi-CHECK plasmid. Mice treated with hydrodynamic injection and untreated animals made up two control groups. Luciferase activity was determined on examination of the harvested liver homogenates. All liposomes showed modest, but significant transfection activity (p<0.05) and were well tolerated. The assemblies examined therefore warrant further development.
Novel epidermal growth factor directed cationic lipoplexes promote in vitro hepatotropic gene targeting.
(2014) Sewbalas, Alisha.; Singh, Moganavelli.; Ariatti, Mario.
The need for the improvement in protocols for cellular gene delivery has propelled cytofectin based liposomes as suitable non-viral gene carriers. The amenability of cationic liposomes to modification enables research based enhancement of their carrier capability. The liposomes formulated in this study show potential for cancer therapeutics, where effective delivery at the molecular level is essential. Cell specific targeting may be attained through cationic vector manipulation to favourably utilise overexpressed cancer cell specific receptors. This study serves as an evaluation of a hepatocyte-directed liposomal gene delivery system, exploiting the abundant epidermal growth factor (EGF) receptors on hepatocellular carcinoma cells (HepG2) in vitro. The inclusion of polyethylene glycol (PEG) served to limit steric hindrance and to increase stability of the formulations. Four liposomes comprising cytofectins 3ß[N-(N',N'-dimethylaminopropane)-carbamoyl] (Chol-T) and N,N-dimethylaminopropylamidosuccinyl-cholesterylformylhydrazide (MS09) at 50 mol%, were formulated through thin film rehydration with dioleoylphosphatidylethanolamine (DOPE) and PEG to generate liposomes that are cationic and have stealth capability. Hepatotropic lipoplexes were formed from EGF adsorption onto formulated liposomes, prior to characterisation and cell culture studies. All liposomes displayed as nano-sized particles (60 – 181 nm) with varying levels of colloidal stablility and distribution as evidenced by transmission electron microscopy and nanoparticle tracking analysis. Moderate to highly cationic lipid : DNA charge ratios were observed by the mobility shift and ethidium bromide dye displacement assays. Broad range protection of plasmid DNA integrity was identifed, with DSPE-PEG2000-grafted liposomes offering greatest shielding against nuclease attack. In vitro cytotoxicity was determined using the MTT assay, and reporter gene expression, was assayed using the luciferase and green fluorescent protein (GFP) reporter gene assays in the receptor positive HepG2 and the receptor negative Chinese Hamster ovary (CHO-K1) cell line. These novel EGF-tagged cationic liposomes displayed negligible cytotoxicity to both cell lines and were capable of high transgene activity in the HepG2 cells compared to the CHO-K1 cells. The Chol-T-EGF liposome significantly (P<0.0001) potentiated transgene targeting, compared to the commercially available transfection reagent, Lipofectin. Targeting was further confirmed from the YI-12 peptide–EGFR competitive transfection determinations in the HepG2 cell line. Results obtained for the luciferase reporter assay was corroborated by the flow cytometric quantification of GFP expression. The size distribution, physicochemical properties and in vitro studies strongly suggest that these targeted lipoplexes should be optimized for future applications in vivo.