Development of a hybrid dextrin hydrogel encapsulating dextrin nanogel as protein delivery system

Dextrin, a glucose polymer with low molecular weight, was used to develop a fully resorbable hydrogel, without using chemical initiators. Dextrin was first oxidized (oDex) with sodium periodate and then cross-linked with adipic acid dihidrazide, a nontoxic cross-linking molecule. Furthermore, a new bidimensional composite hydrogel, made of oxidized dextrin incorporating dextrin nanogels (oDex-nanogel), was also developed. The oDex hydrogels showed good mechanical properties and biocompatibility, allowing the proliferation of mouse embryo fibroblasts 3T3 cultured on top of the gel. The gelation time may be controlled selecting the concentrations of the polymer and reticulating agent. Both the oDex and oDex-nanogel hydrogels are biodegradable and present a 3-D network with a continuous porous structure. The obtained hybrid hydrogel enables the release of the dextrin nanogel over an extended period of time, paralleling the mass loss curve due to the degradation of the material. The dextrin nanogel allowed the efficient incorporation of interleukin-10 and insulin in the oDex hydrogel, providing a sophisticated system of controlled release. The new hydrogels present promising properties as an injectable carrier of bioactive molecules. Both proteins and poorly water-soluble low-molecular-weight drugs are efficiently encapsulated in the nanogel, which performs as a controlled release system entrapped in the hydrogel matrix.     

Hydrodynamic properties of connective-tissue polysaccharides.

The major hydrodynamic properties of the connective-tissue polysaccharides are those that describe polysaccharide-water interaction as embodied in their osmotic-pressure and hydraulic-conductivity properties. This study shows that, for polysaccharides such as chondroitin sulphate, hyaluronate and the heparin-like polysaccharides, their hydrodynamic properties depend primarily on the presence of the uronic residue and the nature of the glycosidic linkage. Other parameters such as the degree of N-acetylation and sulphation were found not to influence these properties to any great extent. These studies particularly delineate structural-functional aspects of the connective-tissue polysaccharides in terms of their primary structure.     

Amphiphilic dendrimeric peptides as model non-sequential pharmacophores with antimicrobial properties

A concept of application of dendrimer chemistry for construction of 'non-sequential pharmacophore', mimicking active conformation of linear antimicrobial peptides, is introduced. It resulted in the synthesis of a family of low- molecular-weight basic peptide dendrimers with antimicrobial properties against Staphylococcus aureus (Gram-positive), Escherichia coli (Gram-negative) and Candida albicans.     

Water-soluble polysaccharides as carriers of paramagnetic contrast agents for magnetic resonance imaging: synthesis and relaxation properties.

Water-soluble, carbohydrate-based, paramagnetic metal chelate derivatives have been investigated as potential organ-selective contrast media for magnetic resonance imaging (m.r.i.). The in vitro proton spin-lattice relaxation properties of compounds with different paramagnetic metals, chelating agents, and carbohydrate matrixes have been studied. Typically, these complexes were 60-260% more efficient proton-relaxation agents than the corresponding low-molecular-weight metal chelates at 10 MHz, but less efficient than the corresponding protein derivatives. As expected, carbohydrates that contained manganese or gadolinium were more effective relaxation agents than iron, copper, erbium, or nickel derivatives.     

Solution properties of pectin polysaccharides — III: Molecular size of heterogeneous pectin chains. Calibration and application of SEC to pectin analysis

Flax pectins, with a low anhydrogalacturonic acid content (AGA≤50%), have been studied by viscometry, light scattering and size exclusion chromatography. After removal of interfering superstructures, intrinsic viscosities were correlated with weight average molecular weights to give a Mark-Houwink coefficient a=0·69. The persistence length of these heterogeneous chains (PI: q=20–25 Å), compared with that of homogalacturonan ones previously studied (PII–PIII: q=67 Å), shows a higher segment density (branched conformation). Using a wide range of experimental data ((η), M_i, K_d) obtained on narrow pectic fractions of known composition, specific calibration curves of the Sephacryl 200/0·2 NaCl/Flax pectins (PI or PII–PIII) system were established. Applied to the indirect characterization of flax pectins, this size exclusion chromatography (SEC) system constitutes a very convenient method for analysing the molecular and macromolecular parameters ((η), M_w, M_n, I_p, ^UV) or for controlling the molecular weight distribution of pectins in flax cell walls during the physiological steps of growth and retting.     

Amphiphilic properties of angiotensin and its fragments

Many biologically active peptides are supposed to interact with specific receptors mainly due to hydrophobic forces. In order to obtain a more detailed information about the peptide molecule behavior at the "water-non-polar-phase" boundary an approach to the calculation of stable conformations on such a boundary has been developed. This approach is used for investigation of the amphiphilic properties of angiotensin and its six fragments. The results of calculations of transfer energies of these peptides from the water environment to the phase boundary are in agreement with the experimental data.     

Myosin chains of myocardial tissue. I. Purification and immunological properties of myosin heavy chains

An antiserum specific to dog myocardial myosin has been developed against highly purified myosin heavy chains. The antiserum is specific for the heavy chains of myosin, giving a single precipitin line in an immunodiffusion assay for either the heavy chains of myosin or native myosin, and does not react with any other myocardial proteins. In such assays myosin acts as a single, uniform antigen. Using this antiserum, a radioimmunoassay has been developed to quantitate myosin in a homogenate of myocardial tissue containing free myosin dissociated from other cellular components.     

Rheological properties of polysaccharides produced by a Zoogloea sp.

A newly isolated marine bacterium, identified as Zoogloea sp., produced two different polysaccharides: one was water-soluble and the other was cell-bound. Both had non-Newtonian, pseudoplastic fluid behaviour and the solutions had low activation energies. The solutions of these polysaccharides showed rheological behaviour over a wide range of pH (2–12) and temperature (20–80 °C), and compatibility with NaCl.     

Antitumor properties of nonstarch polysaccharides: Fucoidans and chitosans

This review deals with the pharmacology of nonstarch polysaccharides, namely fucoidans and chitosans, isolated from marine organisms. The work summarizes information from the international literature on the antitumor activities of native polysaccharides and their derivatives. The structures and physicochemical properties of these polysaccharides are described and the molecular mechanisms of their antitumor and antimetastatic effects are discussed.     

In vitro polyoma DNA synthesis: self-annealing properties of short DNA chains.

Short DNA chains, isolated from in vitro pulse-labeled replicating polyoma DNA, exhibit some degree of self-complementarity (28% resistance to S1 nuclease after self-annealing to plateau levels). This level of self-annealing is not increased if short DNA chains present as free single-stranded DNA after extraction are included in the hybridization, excluding a selective loss of chains from one side of the growing fork and supporting a semi-discontinuous mode of chain growth. This mode also applies to restricted synthesis conditions under which a relative excess of short chains is made, since no increase in the self-annealing of such short chains is observed. The self-annealing that can be measured is higher for the faster sedimenting portion (46%) of the short DNA chains than for the slower sedimenting portion (18.5%), indicating that it is most likely due to contaminating continuously growing strands from the other side of the fork. High self-annealing values (up to 60%) are obtained if virus stocks generating defective DNA are used for infection. Restriction endonuclease (Hpall) characterization of such DNA shows evidence for the presence of multiple origins of replication. One of several possible mechanisms is discussed by which replicating defective DNA can generate self-complementary short chains despite a semi-discontinuous mode of replication.     

X-ray diffraction studies on the connective tissue polysaccharides. Two-dimensional packing schemes for threefold hyaluronate chains.

An extended conformation of sodium and calcium hyaluronate with helical parameters n (number of residues per turn) = 3 and h (axial rise per disaccharide) = 0.95 ± 0.01 nm has been found to pack in a number of two-dimensional arrays. Each of the structures exhibits a variant of a motif consisting of six chains surrounding a “vacant” site. The distribution of chains around this site, together with certain aspects of the periodicity, suggests that there might be a special relationship between this conformation of hyaluronic acid and water.     

Chemical and immunological studies on mycobacterial polysaccharides. 1. Purification and properties of polysaccharides from human tubercle bacilli

Defatted human tubercle bacilli, Aoyama B strain, were extracted with 0.1 n NaOH for 24 hr, and the crude polysaccharide fraction was precipitated by the addition of 5 volumes of ethyl alcohol. A yield of 17.8 g of crude polysaccharides was obtained from 800 g of bacilli. The crude polysaccharide was further fractionated into seven fractions by fractional precipitation with ethyl alcohol. Each fraction was purified by successive chromatography on Dowex 50 and diethylaminoethyl cellulose, and by gel filtration on Sephadex G-75 and G-200. Optical rotation and gas chromatographic analyses of purified polysaccharide showed that these polysaccharides contained glucan mannan, arabinomannan, and arabinogalactan. Each polysaccharide was almost completely free from nitrogen, and no tuberculin reaction was produced by 100 mug of each material. Arabinomannan and arabinogalactan showed precipitin reaction, complement fixation, and passive hemagglutination reaction with rabbit antiserum against heat-killed whole bacilli (Aoyama B). In guinea pigs sensitized with Aoyama B bacilli, arabinomannan and arabinogalactan provoked anaphylactic shock when injected intravenously, and Arthus type reaction when injected intracutaneously. With the use of rabbit antiserum, arabinomannan and arabinogalactan showed passive anaphylactic shock, passive cutaneous anaphylaxis, and Prausnitz-Küstner type reactions in guinea pigs. By immunodiffusion analysis, it was shown that the antigenic determinant of arabinomannan was different from that of arabinogalactan.     

以CasX为例简述新型CRISPR-Cas系统的基本属性和研究方法

在细菌与古菌中广泛存在的CRISPR-Cas系统,作为目前发现的原核生物唯一的适应性免疫系统,抵御着病毒和质粒的入侵.自20世纪80年代首次被发现至今,CRISPR-Cas系统的基本情况逐渐清晰,包括名称缩写、分类、进化关系等方面.近年来,由于第二类CRISPR-Cas系统作为一种有潜力的基因编辑工具而逐渐成为应用研究...     

Preparation and properties of fluorescent polysaccharides

A new method for preparing fluorescein derivatives of polysaccharides is described. These derivatives are prepared by activation of the polysaccharide with cyanogen bromide and subsequent reaction with fluoresceinamine. The optimum conditions for coupling have been established in this report. Using this procedure, we have prepared fluorescein derivatives of a wide variety of polysaccharides. Degrees of substitution in the range of 3.0 X 10(-3) to 2.4 X 10(-2) mol of fluorescein per mole of monosaccharide equivalent were obtained. The fluorescent derivatives are stable: no free fluorescein was detected after incubation at 22 degrees C for 48 h or at -10 degrees C for 4 months. The fluorescein-derivatized polysaccharides were found to have the same potency in inhibiting lectin-mediated hemagglutination as the underivatized polysaccharide. In addition, these fluorescent polysaccharides can be radioiodinated to specific activities exceeding 10(6) dpm/micrograms due to incorporation of 125I into fluorescein. The cell binding properties of 125I-fucoidin and 125I-heparin are indistinguishable from the corresponding underivatized polysaccharides. This general approach for preparing fluorescent polysaccharides should produce useful reagents for localizing and quantifying cell surface carbohydrate-binding proteins (lectins).     

Immobilized glucoamylase: A biocatalyst of dextrin hydrolysis

Heterogeneous biocatalysts of starch conversion based on glucoamylase and carbon-containing carriers were obtained, and their biocatalytic properties in enzymatic hydrolysis of corn dextrins were studied. It was shown that the morphology of the surface carbon layer of carriers markedly affected the properties of biocatalysts. Glucoamylase that was immobilized by adsorption on the surface of carriers covered with a layer of catalytic fibrous or pyrolytic carbon had the maximum enzymatic activity and stability, whereas the biocatalysts prepared on the basis of carriers that had no carbon layer or were covered with graphite-like surface carbon had a low activity and stability.     

Self-assembled dextrin nanogel as protein carrier: controlled release and biological activity of IL-10

Interleukin-10 (IL-10) is an anti-inflammatory cytokine, which active form is a non-covalent homodimer. Given the potential of IL-10 for application in various medical conditions, it is essential to develop systems for its effective delivery. In previous work, it has been shown that a dextrin nanogel effectively incorporated and stabilized rIL-10, enabling its release over time. In this work, the delivery system based on dextrin nanogels was further analyzed. The biocompatibility of the nanogel was comprehensively analyzed, through cytotoxicity (lactate dehydrogenase (LDH) release, MTS, Live, and Dead) and genotoxicity (comet) assays. The release profile of rIL-10 and its biological activity were evaluated in vivo, using C57BL/6 mice. Although able to maintain a stable concentration of IL-10 for at least 4 h in mice serum, the amount of protein released was rather low. Despite this, the amount of rIL-10 released from the complex was biologically active inhibiting TNF-α production, in vivo, by LPS-challenged mice. In spite of the significant stabilization achieved using the nanogel, rIL-10 still denatures rather quickly. An additional effort is thus necessary to develop an effective delivery system for this cytokine, able to release active protein over longer periods of time. Nevertheless, the good biocompatibility, the protein stabilization effect and the ability to perform as a carrier with controlled release suggest that self-assembled dextrin nanogels may be useful protein delivery systems.     

Extracellular Tremella polysaccharides: structure, properties and applications

Tremella sp. is a yeast-like fungus from which polysaccharides can be isolated from either the yeast or the fungus phase, depending on the species. All of the polymers synthesized by these organisms consist of a mannan backbone to which small xylose side chains and glucuronic acid are attached. The main interest in these glucuronoxylomannans is their application in medicine to enhance the immune system.