Separation of polyethylene glycols and amino-terminated polyethylene glycols by high-performance liquid chromatography under near critical conditions.

The separation and characterization of polyethylene glycols (PEGs) and amino-substituted derivatives on common silica-based reversed-phase packing columns using isocratic elution is described. This separation is achieved by liquid chromatography under the near critical conditions (LCCC), based on the number of amino functional end groups without obvious effect of molar mass for PEGs. The mobile phase is acetonitrile in water with an optimal ammonium acetate buffer. The separation mechanism of PEG and amino-substituted PEG under the near LCCC on silica-based packing columns is confirmed to be ion-exchange interaction. Under the LCCC of PEG backbone, with fine tune of buffer concentration, the retention factor ratios for benzylamine and phenol in buffered mobile phases, α(benzylamine/phenol)-values, were used to assess the ion-exchange capacity on silica-based reversed-phase packing columns. To the best of our knowledge, this is the first report on separation of amino-functional PEGs independent of the molar mass by isocratic elution using common C18 or phenyl reversed-phase packing columns.

A facile preparation of novel multifunctional vectors by non-covalent bonds for co-delivery of doxorubicin and gene.

In this study, novel multifunctional ternary complexes of biotinylated transferrin-avidin-biotin-poly(ethylene glycol)-poly(L-glutamate acid)/poly(2-(2-aminoethylamino) ethyl methacrylate)/doxorubicin-poly(L-aspartic acid)/pDNA (TAB/PIC-D/pDNA complexes) were prepared based on polyion complex micelles (PIC) and the avidin-biotin system, which aimed to target co-delivery of anti-cancer doxorubicin and gene. Cytotoxicity studies revealed that PIC-D could have anti-tumor effect on HeLa cells and HepG2 cells; TAB coating could increase the biocompatibility of PIC-D/pDNA complexes and the targeting delivery efficiency of doxorubicin. TAB/PIC-D/pDNA complexes possessed higher transfection efficiency than the unmodified complexes in serum, and transferrin could enhance luciferase expression in HeLa cells and HepG2 cells. Furthermore, confocal laser scanning microscopy showed that doxorubicin and gene could be delivered into HepG2 cells simultaneously by TAB/PIC-D/pDNA complexes. The formation of the ternary complexes provides a facile approach to constructing a multifunctional delivery system for targeted co-delivery of anticancer drugs and gene.

Immobilization of galactose ligands on acrylic acid graft-copolymerized poly(ethylene terephthalate) film and its application to hepatocyte culture.

Surface modification of argon-plasma-pretreated poly(ethylene terephthalate) (PET) films via UV-induced graft copolymerization with acrylic acid (AAc) was carried out. Galactosylated surfaces were then obtained by coupling a galactose derivative (1-O-(6'-aminohexyl)-D-galactopyranoside) to the AAc graft chains with the aid of a water-soluble carbodiimide (WSC) and N-hydroxysulfosuccinimide (sulfo-NHS). The modified PET films were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and water contact-angle measurements. The galactosylated PET films were used as substrates for hepatocyte culture. The effects of surface carboxyl group concentration on the extent of galactose ligand immobilization, the extent of hepatocyte attachment, and the surface morphology were investigated. The amount of the galactose ligands immobilized on the PET surface increased with the AAc polymer graft concentration. AFM images revealed that the surface roughness of the PET film increased after graft copolymerization with AAc, but did not change appreciably with the subsequent immobilization of the galactose ligands. At the surface carboxyl group concentration of about 0.56 micromol/cm(2) or galactose ligand concentration of about 0.51 micromol/cm(2), the hepatocyte culture on the galactosylated surface exhibited the optimum concentration and physiological functions and formed aggregates or spheroids after just 1 day of culture. The albumin and urea synthesis functions of these hepatocytes were comparable to or higher than those of the hepatocytes cultured on the collagen-modified PET substrates.

In vitro release of 5-fluorouracil with cyclic core dendritic polymer.

This paper describes the first synthesis of a series of dendritic polymers with a core of 1,4,7,10-tetraazacyclododecane. This core was allowed to react with methyl acrylate through a Michael addition and was then amidated with ethylenediamine. Repeating the two steps led to controlled molecular weight increasing and branching on the molecular level and produced four direction poly(amide-amine) dendrimers. We successfully synthesized dendrimers from generation 0. 5 to generation 5.5. Each generation was analyzed by Fourier- transform infrared (FT-IR) spectroscopy, 1H NMR and elemental analysis. Titrimetry was also used to determine the number of -NH2 of each full generation (2.0, 3.0, 4.0, 5.0). SEC (size exclusion chromatography) was performed to test the purity of G-3.0, G-4.0 and G-5.0. Parts of the outer layer -NH2 groups of the dendrimers generation 4 and generation 5 were acylated by acetic anhydride. The solubility in water of the dendrimer was thus greatly enhanced. The acetylated dendrimers were then reacted with 1-bromoacetyl-5-fluorouracil to form dendrimer-5FU conjugates. Hydrolysis of the conjugates in a phosphate buffer solution (pH 7.4) at 37 degreesC will release free 5FU. Different generation of dendrimer-5FU conjugates exert marking influence on the amount of 5FU released. The dendritic polymer seems to be a promising carrier for the controlled release of antitumor drugs.

Development of a polymer-enzyme immunoassay method and its application.

Both poly(N-isopropylacrylamide) and poly(N-isopropylacrylamide)-antibody (PINP-Ab)-labelled enzyme adhered quickly and tightly to cellulose acetate/nitrate membrane either below (less efficiently) or above (more efficiently) the lower critical solution temperature, and the retention of PINP-Ab on the membrane increased over 30-fold when compared with the unconjugated Ab. These characteristics were used to develop a novel polymer-enzyme-linked immunoassay method: homogeneous antigen-antibody immune-complexation reaction and a heterogeneous separation process. By using a simple horseradish-peroxidase-labelled antibody as a probe, we applied this method to the detection of human serum hepatitis B surface antigen (HBsAg). This immunoassay system can detect as little as 1 ng/ml of HBsAg. The advantages of this method are: (a) fast homogeneous immune complexation; (b) a rapid heterogeneous separation process; (c) high sensitivity; and (d) low non-specific background.