[Show abstract][Hide abstract] ABSTRACT: Polymeric nanoparticle-based carriers are promising agents for the targeted delivery of therapeutics to the intracellular site of action. To optimize the efficacy in delivery, often the tuning of physicochemical properties (i.e., particle size, shape, surface charge, lipophilicity, etc.) is necessary, in a manner specific to each type of nanoparticle. Recent studies showed an efficient tumor targeting by hydrophobically modified glycol chitosan (HGC) nanoparticles through the enhanced permeability and retention (EPR) effect. As a continued effort, here the investigations on the cellular uptake mechanism and the intracellular fate of the HGC nanoparticles are reported. The HGC nanoparticle, prepared by a partial derivatization of the free amino groups of glycol chitosan (GC) with 5beta-cholanic acid, had a globular shape with the average diameter of 359 nm and the zeta potential of ca. 22 mV. Interestingly, these nanoparticles showed an enhanced distribution in the whole cells, compared to the parent hydrophilic GC polymers. In vitro experiments with endocytic inhibitors suggested that several distinct uptake pathways (e.g., clathrin-mediated endocytosis, caveolae-mediated endocytosis, and macropinocytosis) are involved in the internalization of HGC. Some HGC nanoparticles were found entrapped in the lysosomes upon entry, as determined by TEM and colocalization studies. Given such favorable properties including low toxicity, biocompatibility, and fast uptake by several nondestructive endocytic pathways, our HGC nanoparticles may serve as a versatile carrier for the intracellular delivery of therapeutic agents.
[Show abstract][Hide abstract] ABSTRACT: To make stable and biocompatible non-viral gene carriers for therapeutic gene therapy, we developed a cationic lipid-based emulsion (CLE) prepared by an oil-in-water (O/W) emulsion method, wherein squalene oil was used as an oil core and the cationic lipid, 1,2-dioleoyl-sn-glycero-3-trimethylammonium-propane (DOTAP), was employed as an emulsifier. To evaluate in vivo characteristics such as toxicity and time-dependent gene expression, a bioluminescence reporter gene in pCMV-luc plasmid DNA was simply mixed with CLE in aqueous condition, resulting in a CLE/DNA complex. The CLE/DNA complex was optimized to form a compact and stable nano-sized particle by adding different amounts of plasmid DNA, and an optimal cationic lipid-to-DNA (C/D) weight ratio of 4 was identified. Freshly prepared CLE/DNA complex, with a C/D of 4, showed a high transfection efficiency and minimal cytotoxicity in vitro, compared to controls of a liposome (DOTAP)/DNA complex and a branched poly(ethyleneimine) (Mw=25 kDa) (bPEI)/DNA complex, respectively. The in vivo characteristics of the CLE/DNA complex were evaluated after intravenous injection into Balb/c mice. Time-dependent gene expression data in vivo were obtained using a non-invasive, whole animal bioluminescence imaging system. These data showed that the CLE/DNA complex offered prolonged high-level gene expression for 1 week, particularly in the liver and spleen. On the other hand, the controls of DOTAP/DNA complex and bPEI/DNA complex showed a relatively lower gene expression, because of the unstable and toxic properties of the control carriers. Our in vivo gene expression data demonstrate the potential of the CLE/DNA complex as a non-viral gene carrier for in vivo gene delivery.
[Show abstract][Hide abstract] ABSTRACT: A cationic emulsion containing an insulin expression plasmid was prepared for the treatment of type 1 diabetic mellitus (DM) in vivo. A rat proinsulin-1 gene was inserted to EBV-based plasmid vectors containing CAG promoter. Cationic emulsion composed of DOTAP and squalene was complexed with the plasmid DNA. An intravenous injection of cationic emulsion containing proinsulin gene decreased blood glucose levels for 7 days within normal range. The cationic emulsion exerted more profound effect on blood glucose levels compared to naked DNA. RT-PCR results confirmed that the proinsulin was expressed in several organs containing liver, lung, spleen, and kidney. The refractory response was invoked by multiple injections of naked DNA or cationic emulsion/DNA complex, which was later proven to be an immune response against expressed proinsulin. Therefore, the cationic emulsion showed a promising result as a novel insulin gene therapy vehicle by decreasing blood glucose level for a month.
[Show abstract][Hide abstract] ABSTRACT: A new cationic emulsion system with high density was prepared increasing in vitro transfection efficiencies of adherent cells. Lipiodol with a density of 1.3 (g/ml) was selected to increase the density of the DNA/emulsion complex. Cationic lipid emulsions were formulated with mixtures of lipiodol and squalene as the oil phase and 1,2-dioleoyl-sn-glycero-3-trimethylammonium-propane (DOTAP) as a cationic lipid. These emulsions were used to find the correlation between the density and the in vitro transfection efficiency. The physical characteristics of the new emulsion formulations were also determined. Heavier DNA/cationic lipid emulsion complex showed higher in vitro transfection efficiency on adherent cell lines in the presence of 10% serum compared to lighter ones. The cationic lipid emulsion formulated with lipiodol and DOTAP was more stable and showed better in vitro transfection efficiency than other carriers without lipiodol. Due to the high density of the carrier, the DNA/carrier complex sank to the bottom of the wells, thereby increasing the contact between the complex and adherent cells. The new lipiodol emulsion with high density showed superior transfection activities on adherent cells in the presence of serum.