You Kyoung Kim

Degradable polyethylenimines as DNA and small interfering RNA carriers

Gene therapy is a powerful approach in the treatment of a wide range of both inherited and acquired diseases. Nonviral delivery systems have been proposed as safer alternatives to viral vectors because they avoid the inherent immunogenicity and production problems that are seen when viral systems are used. Many cationic polymers, including high-molecular-weight polyethylenimine (PEI) have been widely studied as gene-delivery carriers, both, in vitro and in vivo. However, interest has recently developed in degradable polymeric systems. The advantage of degradable polymer is its low in-vivo cytotoxicity, which is a result of its easy elimination from the cells and body. Degradable polymer also enhances transfection of DNA or small interfering RNA (siRNA) for efficient gene expression or silencing, respectively. This review paper summarizes and discusses the recent advances with degradable PEIs, such as cross-linked and grafted PEIs for DNA and siRNA delivery.

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.

Glucosylated Polypropylenimine Dendrimer as a Novel Gene Carrier

Polypropylenimine (PPI) dendrimers have been used by many researchers as gene delivery carriers due to their high functionality. Glucose as a kind of carbohydrate is biocompatible and hydrophilic. In this study, we synthesized glucosylated PPI (G-PPI) dendrimers to reduce cytotoxicity. Glucose substitution of G-PPI dendrimers was determined by the sulfuric acid micromethod. The G-PPI dendrimer was complexed with plasmid DNA in various N/P ratios, and the complex was characterized. G-PPI dendrimers showed good DNA binding ability and high protection of DNA from nuclease attack. The G-PPI dendrimer had low cytotoxicity compared to PPI dendrimer by cytotoxicity assay. Also, transfection efficiency was influenced by glucosylation degree and the transfection efficiency for the G-PPI-5 was slightly higher than that of PPI dendrimer in HeLa cell line.

Alginate-Coated Thiolated Chitosan Microspheres for an Oral Drug Delivery System In Vitro

Thiolated polymers have been studied by many researchers because of the mucoadhesive properties of thiol group. Alginate is a natural and biocompatible polymer that has been widely used in drug delivery. In this study, thiolated chitosan microspheres (TCMs) were prepared by ionic gelation process with tripolyphosphate and then, the bovine growth hormone (BGH) was loaded as a model drug. Finally, the BGH-loaded TCMs (BTCMs) were coated with alginate to improve the stability in gastrointestinal (GI) track. The alginate-coated BTCMs (ABTCMs) were observed as spherical shapes. The average particle sizes of ABTCMs were 6.97±0.55 -m and the sizedistribution was shown uniformly. Release of BGH from ABTCMs was decreased by coating with alginate and increased rapidly with the change in medium pH from 1.2 to 7.4. Results indicate that the ABTCMs have a potential as a drug carrier for oral drug delivery.

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.

Injectable polymeric carriers for gene delivery systems

Abstract: Cationic polymers that have shown significant promise as gene delivery agents are more effective than the state-of-the art, commercially available non-viral systems. Gene delivery in vivo involves interactions with the biophase (the effect site of drug) prior to reaching the target cells which complicates efforts to understand the mechanism of the delivery process. The ability to incorporate genetic materials such as DNA, RNA and siRNAs into functionalized nanoparticles demonstrates a new era. In this chapter, we highlight the basic overview of injectable polymeric gene carriers that have been reported as safe and successful vectors, their formulations and in vivo success thereof. In addition, we outline various strategies for designing polymeric carriers to overcome various biological barriers as successful gene delivery vectors.

All-Trans Retinoic Acid (atRA) Release from atRA-Loaded Folate-Poly(Ethylene Glycol)/Polyethylenimine Nanoparticles for Folate-Mediated Tumor Targeting

To improve the specific accumulation in tumor sites and aqueous solubility of atRA, the core-shell type of folate-PEG-g-PEI/atRA nanoparticles were prepared by complexation between cationic PEI segments in the copolymers and anionic charged atRA, and then characterized by 1HNMR, ELS, XRD, and TEM. In vitro atRA release from the nanoparticles was investigated as a function of drug content in sink condition. Cytotocicity of atRA against HepG2, KB cell lines were also evaluated by MTT assay. The lower the drug content, the faster atRA release. atRA incorporated in folate-PEG-g-PEI/atRA nanoparticles showed much higher cytotoxic effect compared with atRA itself.