To study the electrostatic interaction between two ionic polymer surface, a polyester film surface was graft-polymerized with a cationic monomer, N,N-dimethylaminoethyl methacrylate and an anionic monomer, acrylic acid. When the oppositely charged film pair was brought into contact in the presence of water, they showed strong adhesion instantaneously in water. The adhesion interaction was studied with both shear strength method and atomic force microscopy. The interaction depended on the graft density and the ionic nature of the graft chains. The addition of salt to the medium of the measurement caused a remarkable reduction in the adhesive interaction. These interactions were attributed to the coulombic force between the grafted ionic polymer chains.

To obtain polymer surfaces having different zeta potentials, a poly(ethylene terephthalate) (PET) film surface was graft-poly-merized with an anionic monomer, acrylic acid (AAc) , and a cationic monomer, N,N-dimethylaminoethyl methacrylate (DMA EMA) . In addition, a cellulose film was surface-modified with Chloroacetic acid to introduce anionic carboxyl groups and N,N-dimethylaminopropyl acrylamide (DMAPAA) to introduce cat-ionic dimethylamino groups. Through these surface modifications we could obtain films having zeta potentials ranging from /39 to -58 mV. Adhesive interaction in water between two surfaces of these films was measured with a tensile testing method after lapping the two surfaces in water. When one film was surface-grafted with cationic polymer chains, it exhibited significant adhesion instantaneously in water toward the other surface with a negative zeta potential, such as the surface-modified cellulose films, quartz, and the unmodified PET film. The quartz surface showed a detectable attractive force toward the cationic cellulose surface, but the force was weaker than that toward the cationically grafted surface. Apparently, no correlation was found between the zeta potential of the surfaces and their adhesive strength.

Delivery of oligonucleotide to specific cells and maintenance of its biological function are important for nucleic acid therapy. The objective of this paper is to demonstrate that galactosylated low molecular weight chitosan (gal-LMWC) is a safe and effective vector of antisense oligonucleotide (ASO) and plasmid DNA for the hepatocyte targeting delivery. Gal-LMWC has been successfully prepared and MTT cytotoxic assay shows that cytotoxicity of gal-LMWC is lower than that of high molecular weight chitosan (HMWC) and low molecular weight chitosan (LMWC) in HepG2 cells. Using a complex coacervation process, gal-LMWC can form stable nano-complexes with plasmid DNA or with ASO by the electrostatic interaction. The morphometrics, particle size, and the zeta potential of gal-LMWC/ASO complexes and gal-LMWC/plasmid DNA complexes are very similar. The transfection efficiency by using gal-LMWC vector is significantly higher than that of naked DNA or naked ASO in HepG2 cells. Transfection efficiency of gal-LMWC/ASO complexes and gal-LMWC/plasmid DNA complexes depends on the molar ratio of the positive chitosan amino group and the negative DNA phosphate group (N/P ratio) strongly. Inhibition experiments confirm that the enhanced transfection efficiency is due to the ASGR mediated endocytosis of the gal-LMWC/ASO complexes or gal-LMWC/DNA complexes. These results suggest that gal-LMWC can be used in gene therapy to improve the transfection efficiency in vitro and in vivo.

The chlorophenol chemicals(CPs) are a major class of widely distributed and frequently occurring persistent environmental pollutants. Pentachlorophenol (PCP) has been proposed to be procarcinogen in rodents and in possibly human beings. Human beings also easily expose to other chlorophenol chemicals, including 4-chlorophenol (CP), 2,4-dichlorophenol (DCP),2,3,4-trichlorophenol(TCP), prompting this investigation of their comparative cytotoxic effects and cell death mechanisms, assayed in fibroblast L929 cells, The effective concentration for half-maximal response (EC50) values at 24 h for CP, DCP, TCP, and PCP are 2.18, 0.83,0.46, and 0.11 mmol/L respectively and the EC50 values at 48 h are 1.18, 0.13, 0.08, and 0.06 mmol/L respectively by using 3-(4,5-dimethylthiazd-2-yl)-2, 5-diphenyltentrazolium bromide (MTT) reduction assay. A clear structure-activity relationship was observed between toxicity of CPs and their octanol-water partition coefficients. The further studies indicate that CP, DCP, and TCP induce apoptosis in L929 cells in a concentration or time-dependent manner, but PCP mediates cell death more characteristic of necrosis than apoptosis. These results not only demonstrate that L929 cell growth inhibition bioassay may be useful to provide the comparative evaluation of toxicity of CPs in vitro, but also implicate that CP, DCP, TCP, in comparison with PCP, can induce L929 cell death by apoptosis, resulting in lower procarcinogensis, which may help to elucidate the molecular basis for the adverse health effects associated with CPs exposure.

Chitosan has the potential for DNA complexation and is useful as a non-viral vector for gene delivery. Highly purified low molecular weight chitosan (LMWC) was prepared. Lactobionic acid (LA) bearing galactose group was coupled with LMWC for liver-specificity. A series of galactosylated-LMWC (gal-LMWC) samples covering a range of galactose group contents were prepared. The chitosan/DNA complexes were obtained using a complex coacervation process. Gal-LMWCs were used to transfer pSV-_-galactosidase reporter gene into human hepatocellular carcinoma cell (HepG2), L-02, SMMC-7721, and human cervix adenocarcinoma cell line (HeLa) cell lines in vitro. Transfection efficiency of gal-LMWCs was evaluated by _-galactosidase assay and compared with those of lipofectin, calcium phosphate (CaP), high molecular weigh chitosan (HMWC) and LMWC. Gal-LMWC/DNA complex shows a very efficient cell selective transfection to hepatocyte. The transfection efficiency of gal-LMWCs increased with the improvement of the galactosylation degree. Cytotoxicity of gal-LMWCwas determined by 3-(4,5-dimethylthiazd-2-yl)-2,5-diphenyltentrazolium bromide (MTT) assay and the results show that the modified chitosan has relatively low cytotoxicity, giving the evidence that the modified chitosan vector has the potential to be used as a safe gene-delivery system.