Jae Woon Nah

Preparation of alginate/galactosylated chitosan scaffold for hepatocyte attachment.

Galactose-carrying lactobionic acid was covalently coupled with chitosan for determining hepatocyte specificity. Galactosylated chitosan (GC) was reacted with Ca-alginate (ALG) gel through the electrostatic interaction of carboxylic groups of alginate with amine groups of GC. Highly porous, three-dimensional sponge composed of ALG and GC was prepared to provide specific hepatocyte recognition signals and enhance the mechanical property of the ALG sponge. Observation of the sponge through scanning electron microscopy revealed that sponge was a highly porous microstructure with interconnected pores. Porosity and pore size of the sponge were greatly dependent on the content and molecular weight of GC, and freezing temperature. The mechanical property of the ALG/GC sponge was enhanced with an increase of the GC content. Spheroid formation and viability of hepatocytes of the ALG/GC sponge were higher than those of the ALG one.

Methotrexate-Incorporated Polymeric Micelles Composed of Methoxy Poly(ethylene glycol) Grafted Chitosan

In this study, methotrexate (MTX)-encapsulated polymeric micelles using methoxy poly(ethylene glycol) (MPEG)-grafted chitosan (ChitoPEG) copolymer were prepared. The MTX-incorporated polymeric micelles of ChitoPEG copolymer has a particle size of around 50-100 nm. In 1H nuclear magnetic resonance (NMR) study, the specific peaks of MTX disappeared in heavy water (D2O) and only the specific peak of MPEG was observed, while all of the peaks were confirmed in dimethyl sulfoxide (DMSO). These results indicated that MTX was complexed with chitosan and then formed an ion complex inner-core of the polymeric micelle in an aqueous environment. The drug contents of the polymeric micelle were around 4∼12% and the loading efficiency of MTX in the polymeric micelles was higher than 60% (w/w) for all of the formulations. The cytotoxicity of MTX and MTX-incorporated polymeric micelle against CT26 tumor cells was not significantly changed.

Synthesis and Characterization of Thermosensitive Nanoparticles Based on PNIPAAm Core and Chitosan Shell Structure

Noble thermosensitive nanoparticles, based on a PNIPAAm-co-AA core and a chitosan shell structure, were designed and synthesized for the controlled release of the loaded drug. PNIPAAm nanoparticles containing a carboxylic group on their surface were synthesized using emulsion polymerization. The carboxylic groups were conjugated with the amino group of a low molecular weight, water soluble chitosan. The particle size of the synthesized nanoparticles was decreased from 380 to 25 nm as the temperature of the dispersed medium was increased. Chitosan-conjugated nanoparticles with 2∼5 wt% MBA, a crosslinking monomer, induced a stable aqueous dispersion at a concentration of 1 mg/1 mL. The chitosan-conjugated nanoparticles showed thermosensitive behaviors such as LCST and size shrinkage that were affected by the PNIPAAm core and induced some particle aggregation around LCST, which was not shown in the NIPAAm-co-AA nanoparticles. These chitosan-conjugated nanoparticles are also expected to be more biocompatible than the PNIPAAm core itself through the chitosan shell structures.

Glucosylated polyethylenimine as a tumor-targeting gene carrier.

Glucosylated polyethylenimine (GPEI) was synthesized as a tumor-targeting gene carrier through facilitative glucose metabolism by tumor glucose transporter. Particle sizes of GPEI/ DNA complex increased in proportion to glucose content of GPEI, whereas surface charge of the complex was not dependent on glucosylation, partially due to inefficient shielding of the short hydrophilic group introduced. GPEI with higher glucosylation (36 mol-%) had no cytotoxic effect on cells even at polymer concentrations higher than 200 μg/mL. Compared to unglucosylated PEI, glucosylation induced less than one-order decrease of transfection efficiency. Transfection of GPEI/DNA complex into tumor cells possibly occurred through specific interaction between glucose-related cell receptors and glucose moiety of GPEI. Gamma imaging technique revealed GPEI/DNA complex was distributed in liver, spleen, and tumors.

A Poly(β-Amino Ester) of Spermine and Poly(ethylene Glycol) Diacrylate as a Gene Carrier

Vectors are vital aspect of gene delivery system which decides the success of gene therapy. Efficient transfection with minimum or no toxicity, are two principal aims of any gene delivery system. In this our study, we rationally developed biodegradable water soluble poly(ßamino ester) (PAE) based on spermine (SPR) and poly (ethylene glycol) (PEG), by Michael-type addition reaction and further studied for its potential as a gene carrier. Confirmation of synthesized PAE was done by proton NMR spectroscopy. In gel retardation assay, the PAEs have shown good DNA binding ability over wide range of polyplexes. The addition of PEG over SPR resulted in a novel PAE with higher degree of safety and transfection efficiency as compared with polyethylenimine 25K (PEI) when studied in 293T human kidney carcinoma cells.

Enhanced gene delivery system using disulfide-linked chitosan immobilized with polyamidoamine

AbstractWe developed a polyamidoamine (PAMAM) conjugated disulfide-linked chitosan (dsCS-PAM) for nonviral gene delivery. At weight ratio of 128, dsCS and dsCS-PAM showed positive zeta potential of around 9.5 mV and 14.5 mV, respectively, demonstrating their ability to form complexes with plasmid DNA (pDNA) for cell transfection. CS-PAM and dsCS-PAM formed complexes with pDNA in a reducing environment containing 5 mM DLdithiothreitol (DTT) at weight ratio 32 and 16, respectively. PAMAM conjugated chitosan derivatives, dsCS-PAM and CS-PAM, showed higher in vitro transfection efficiency than unconjugated derivatives dsCS and CS. Approximately 80% of A549 and 293 cells were viable in the presence of up to 100 μg/mL of dsCS-PAM. The results of this study demonstrate that dsCS-PAM has the potential to be a safe gene delivery carrier.n

Enhance of Tumor Targeting by Receptor-Mediated Endocytosis Using Low Molecular Water-Soluble Chitosan Nanoparticles Loaded with Anticancer Agent

In this study, we prepared using low molecular weight water-soluble chitosan nanoparticle loaded paclitaxel (LMWSC-NPT) and investigated the potential as a drug carrier which is able to accumulate in the tumor site. In the experiment of receptor-mediated endocytosis, LMWSC-NPT was treated with sodium azid (NaN3) as an inhibitor of endocytosis process. As results, the antitumor activity of LMWSC-NPT treated with sodium azid didn’t show but LMWSC-NPT was shown the high antitumor activity. Therefore, LMWSC-NPs modified with hydrophobic group will be useful anticancer agent carrier via receptor-mediated endocytosis.

Simple nanophotosensitizer fabrication using water-soluble chitosan for photodynamic therapy in gastrointestinal cancer cells

The polysaccharide chitosan has abundant cationic amine groups, and can form ion-complexes with anionic molecules such as the strong photosensitizer chlorin e6 (Ce6). In this study, water-soluble chitosan (WSC) was used to fabricate Ce6-incorporated nanophotosensitizers (Abbreviated as ChitoCe6 nanophotosensitizer) via a self-assembling process. This was accomplished by dissolving WSC in pure water and then directly mixing the solution with solid Ce6 causing ion complex formation between WSC and Ce6. The resulting nanophotosensitizer was spherical in shape and had a particle size of less than 300nm. The photodynamic effect of ChitoCe6 nanophotosensitizer was evaluated using gastrointestinal (GI) cancer cells. At in vitro study using SNU478 cholangiocarcinoma cells, ChitoCe6 nanophotosensitizer showed improved Ce6 uptake by tumor cells, reactive oxygen species production, and cellular phototoxicity. An in vivo study using SNU478-bearing nude mice showed that the ChitoCe6 nanophotosensitizer efficiently accumulated in the tumor tissue and inhibited tumor growth more than treatment with Ce6 alone. Furthermore, ChitoCe6 nanophotosensitizer was also efficiently absorbed through tissue layers in an ex vivo study using porcine bile duct explants. ChitoCe6 nanophotosensitizer showed enhanced photosensitivity and photodynamic effects against cancer cells in vitro and in vivo. We present ChitoCe6 nanophotosensitizer as a promising candidate for photodynamic therapy of GI cancer.

Galactosylated Chitosan/Carbonate Apatite Nanohybridization for Cell Specificity and High Transfection Efficiency as a DNA Carrier

The strategies developed for gene delivery are generally classified into two categories of viral and non-viral vectors. The limitation of viral vectors, which have problems including toxicity, immunogenicity and inflammatory response has led to the development of a novel, synthetic vectors based on non-viral vectors. Chitosan, one of non-viral vectors, has been a good candidate in gene delivery field. Moreover, galactosylated chitosan (GC) had the specific recognition of hepatocytes by galactose in the GC. Also, carbonate apatite increased the rate of DNA endocytosis and the efficiency of gene transfer. We describe here a new concept for improving cell specificity and transfection efficiency by hybridization of carbonate apatite (CAp) with GC. The complex formation was confirmed by agarose gel electrophoresis. The complex optimized through controlling calcium ion and charge ratio was evaluated on the cell specificity and transfection efficiency.

Novel Poly(Ester Amine) Based on Polycaprolactone and Polyethylenimine as a Gene Carrier: Effect of Hydrophobicity on Transfection Efficiency and Cytotoxicity

Novel, biodegradable poly(ester amine)s (PEAs) were synthesized using hydrophobic polycaprolactone diacrylate (PCLDA) and highly cationic polyethylenimine (PEI). This novel gene carrier can form stable DNA complexes with particle sizes around 200 nm, and showing excellent transfection efficiency and relatively low cytotoxicity compared with PEI 25K. Effect of hydrophobicity on transfection efficiency and cytotoxicity was profound and was relatively important parameter for the success of gene delivery.