Synthesis and Cytotoxic Activity of Oxidized Galactomannan/ADR Conjugate

Abstract

Many polysaccharides are expected to apply as biomaterials because they generally show good biocompatibilities and biodegradabilities. It has recently been reported that the saccharides play important roles in biological recognition and the transmission of biological information on a cellar surface. Galactomannan (GalM) is a polysaccharide whose main chain is composed of β-1,4-linked mannose units only. It has some branching α-galactose residues at the C-6 position of mannose units. Therefore, it was of interest of us to use GalM as a drug carrier which was targeted to hepatocyte having a galactose receptor on its cellar surface. Dicarboxy-galactomannan (DC-GalM), which has reactive functional groups and is a carboxylic acid derivative of galactomannan, was prepared by IO^4-/CIO^2- oxidation of GalM. The obtained DC-GalM showed specific binding with maclura pomifera (MPA) [1] which has a specificity to α-galactose. Moreover, DC-GalM showed selective incorporation into hepatocyte. Adriamycine (ADR), which is one of the most prominent anticancer agents, was immobilized to DC-GalM. The DC-GalM/ADR conjugate showed specific cytotoxic activity against HepG2 human hepatoma cells which have a galactose receptor on the cell surface, compared with Hela utrocervical carcinoma cells which have no galactose receptor.     

Vinyl Polymerization. 439. Vinyl Polymerization Initiated by Poly(Ethylene Glycol] Diglycolic Acid or its Sodium Salt

Abstract

The polymerization of some kinds of vinyl monomer was found to occur in aqueous solutions of poly(ethylene glycol) diglycolic acid (PEG Acid) or sodium poly(ethylene glycol) diglycolate (PEG Acid Na) through radical mechanisms without any further initiator, as a so-called “uncatalyzed polymerization.” Although the initiating radical species for PEG Acid was determined to be the same as that for PEG Acid Na by means of the spin-trapping technique, the initiating ability of PEG Acid was higher than that of PEG Acid Na. These results are assumed to be attributable to the difference in the initiation mechanisms of the two systems and in the incorporating abilities of monomer into the hydrophobic areas formed by PEG Acid and PEG Acid Na.     

Vinyl Polymerization. 436. Effect of Magnetic Field on Uncatalyzed Polymerization

The radical polymerization of vinyl monomers initiated with several kinds of hydrophilic macromolecule was carried out in a magnetic field. The magnetic field promoted the polymerization; the conversion of monomers and the molecular weight of the polymers obtained increased with increasing field strength in the range of 0–0.1 T. The dependence of the composition and tacticity of the mother polymer on the magnitude of the magnetic field was studied. Using graft or block copolymers, which consisted of hard and soft segments, the effect of a magnetic field was further investigated. The degree of hardness and tightness of the hydrophobic areas (reaction areas) formed by the mother polymer in the aqueous solution was found to affect the magnetic field effect on the uncatalyzed polymerization. The overall activation energy obtained in the magnetic field was almost equal to that obtained without a magnetic field.     

Index Abstracts

Abstract

Calorimetric titrations have been performed in anhydrous acetonitrile at 25°C to give the complex stability constants (K _s) and the thermodynamic parameters (ΔGΔ, ΔHΔ and ΔSΔ) for the complexation of light lanthanoid(III) nitrates (La-Gd) with N-benzylaza-21-crown-7 3. Data analyses, assuming 1:1 stoichiometry, were successfully applied to all light lanthanoid-azacrown ether combinations employed. Using the present and previous data on 15- to 21- membered N-benzylazacrown ethers 1–3, the effect of ring size upon complexation behavior was discussed comparatively and globally from the thermodynamic point of view. The complexation behaviors are analyzed in terms of the size-fit concept, N-substituent coordination numbers, and lanthanoid's surface charge density. Thermodynamically the complexation of light lanthanoids with azacrown ethers is enthalpy-driven, while the cation selectivity is generally entropy-driven in acetonitrile.     

Sequence Dependence of Fluorescent Quenching of Chromophores Covalently Bonded to Oligo-DNAs before and after Duplex Formation

The labeling of oligo- and polynucleotides with fluorescent probes is an important technique for the analysis of DNAs and RNAs. The effect of duplex formation with complementary oligo-DNA on the quenching behavior of two fluorescent chromophores (eosin, Eo and tetramethylrhodamine, TMR) attached to the 5′-terminal of various 10mer oligo-DNAs was investigated and the dependence of the quenching on DNA base sequence is discussed. We found that guanine residues played a major role in the quenching of the fluorescence of the chromophores. Guanine residues on the complementary DNA near the chromophores, in particular, had a significant influence on the quenching.     

Unprecedented Sequence Control and Sequence‐Driven Properties in a Series of AB‐Alternating Copolymers Consisting Solely of Acrylamide Units

Herein, we report a method to synthesize a series of alternating copolymers that consist exclusively of acrylamide units. Crucial to realizing this polymer synthesis is the design of a divinyl monomer that contains acrylate and acrylamide moieties connected by two activated ester bonds. This design, which is based on the reactivity ratio of the embedded vinyl groups, allows a “selective” cyclopolymerization, wherein the intramolecular and intermolecular propagation are repeated alternately under dilute conditions. The addition of an amine to the resulting cyclopolymers afforded two different acryl amide units, i.e., an amine‐substituted acryl amide and a 2‐hydroxy‐ethyl‐substituted acryl amide in alternating sequence. Using this method, we could furnish ten types of alternating copolymers; some of these exhibit unique properties in solution and in the bulk, which are different from those of the corresponding random copolymers, and we attributed the differences to the alternating sequence.     

Formation of polymeric micelles with amino surfaces from amphiphilic AB‐type diblock copolymers composed of poly(glycolic acid lysine) segments and polylactide segments

Amphiphilic AB‐type diblock copolymers composed of hydrophobic poly(L ‐lactide) (PLA) segments and hydrophilic poly(glycolic acid lysine) [poly(Glc‐Lys)] segments with amino side‐chain groups self‐associated to form PLA‐based polymeric micelles with amino surfaces in an aqueous solution. The average diameter of the loose core–shell polymeric micelles for poly(Glc‐Lys) [number‐average molecular weight (M_n) = 1240]‐b‐PLA (M_n = 7000) obtained by a dimethyl sulfoxide/water dialysis method was estimated to be about 50 nm in water by dynamic light scattering measurements. The size and shape of the obtained polymeric micelles were further observed with transmission electron microscopy and atomic force microscopy. To investigate the possibility of applying the obtained PLA‐based polymeric micelles as bioabsorbable vehicles for hydrophobic drugs, we tested the entrapment of drugs in poly(Glc‐Lys) (M_n = 1240)‐b‐PLA (M_n = 7000) micelles and their release with doxorubicin as a hydrophobic drug. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1426–1432, 2002     

(15N) acetamide in polar solvents: Hindered internal rotation and intermolecular interactions

The ¹H spectrum of (¹⁵N)acetamide has been measured in dimethyl sulphoxide (DMSO), methyl propyl ketone (MPK), 1,3-dioxane, 1,4-dioxane, D₂O, acetonitrile and pyridine-d₅ at various temperature intervals within the range of 278–343 K. From the temperature dependence of the NMR spectra of the amide protons, the free energy of activation, ΔG^≠, for hindered rotation about the central C? N bond was determined by means of total line shape analysis in the four solvents DMSO, MPK and the two dioxanes. Observed values of ΔG^≠ (298 K) (72.7 in DMSO, 70.1 in MPK, 70.0 in 1,3-dioxane and 70.1 kJ mol¹ in 1,4-dioxane) were not very sensitive to the choice of solvent or concentration. The concentration dependence of the internal chemical shift between the amide protons was studied in MPK, D₂O, acetonitrile and pyridine-d₅. The free energy of activation and the internal chemical shift are discussed on the basis of solvent-amide and amide–amide specific hydrogen bonding interactions, and in comparison to the results of molecular orbital calculations.     

Oxidation of sec‐alcohols with Ru(II)‐bearing microgel star polymer catalysts via hydrogen transfer reaction: Unique microgel‐core catalysis

Oxidation of sec‐alcohols was investigated with ruthenium‐bearing microgel core star polymer catalysts [Ru(II)‐Star]. The star polymer catalysts were directly prepared via RuCl₂(PPh₃)₃‐catalyzed living radical polymerization of methyl methacrylate (MMA), followed by the arm‐linking reaction with ethylene glycol dimethacrylate ( 1 ) in the presence of diphenylphosphinostyrene ( 2 ). The Ru(II)‐Star efficiently and homogeneously catalyzed the oxidation of 1‐phenylethanol ( S1 ) to give a corresponding ketone (acetophenone) in higher yield (92%) than the analogs of polymer‐supported ruthenium complexes. Importantly, the star catalyst afforded high recycling efficiency in the oxidation. They held catalytic activity against three times catalysis even though they were recovered under air‐exposure, whereas the conventional RuCl₂(PPh₃)₃ lost the activity for same recycling procedure due to the deactivation by oxygen. The stability of the star catalysts during the recycle experiment was confirmed by detailed spectroscopic characterization. The star polymers also catalyzed oxidation for a wide range of sec‐alcohols with aromatic and aliphatic groups. The substrate affinity was different from that with RuCl₂(PPh₃)₃, suggesting the unique selectivity caused by the specific structure. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.