Dextran biological properties

The biological properties of dextran again vary with strain. 

Significant research has been directed toward the use of polyelectrolyte complexes as blood compatible materials. Several investigators found that water-insoluble polyelectrolyte complexes can suppress blood coagulation [487-490]. Davison and coworkers reviewed and studied the biological properties of water-soluble polyelectrolyte complexes [491] between quatemized poly(vinyl imidazole) or polyvinyl pyridine) and excess sulfonated dextran or poly(methacrylic acid). By forming complexes with a stoichiometric excess of anionic charge, a more compact conformation with anionic character was obtained. 

The biological properties of dextran are a function of its molecular structure, molecular weight and distribution of molecular weights. Dextran 70 gives an increase in plasma volume, corresponding to the volume injected. After infusion of Dextran 70, about 30% is excreted by normal renal function within 6 hours and in all about 40% within 24 hours. The rest is degraded in the body at a rate of 70 mg/kg body-weight per day. 

Sephadex (a dextran cross-linked with epichlorohydrin) has been used as an affinity matrix for the separation of [ I]-concanavalin A from the unlabelled lectin. If this technique is successful with other I-labelled proteins, it would help to overcome the uncertainty of whether or not biological properties displayed by labelled materials arise from contamination by the unlabelled material. 

Abstract Carbohydrates have been investigated and developed as delivery vehicles for shuttling nucleic acids into cells. In this review, we present the state of the art in carbohydrate-based polymeric vehicles for nucleic acid delivery, with the focus on the recent successes in preclinical models, both in vitro and in vivo. Polymeric scaffolds based on the natural polysaccharides chitosan, hyaluronan, pullulan, dextran, and schizophyllan each have unique properties and potential for modification, and these results are discussed with the focus on facile synthetic routes and favorable performance in biological systems. Many of these carbohydrates have been used to develop alternative types of biomaterials for nucleic acid delivery to typical polyplexes, and these novel materials are discussed. Also presented are polymeric vehicles that incorporate copolymerized carbohydrates into polymer backbones based on polyethylenimine and polylysine and their effect on transfection and biocompatibility. Unique scaffolds, such as clusters and polymers based on cyclodextrin (CD), are also discussed, with the focus on recent successes in vivo and in the clinic. These results are presented with the emphasis on the role of carbohydrate and charge on transfection. Use of carbohydrates as molecular recognition ligands for cell-type specific dehvery is also briefly... 

For the extraction of proteins, aqueous two-phase systems (ATPS) are preferred over organic solvents, which usually denature the proteins and render them biologically inactive. They consist of polyethylene glycol (PEG), and a salt (e.g., potassium phosphate) or dextran in water. At concentrations above a critical value, the mixture separates into two phases—one rich in PEG and the other in dextran or salt. In industrial systems, salts are more commonly used because they are relatively inexpensive as compared to dextran. The MW, charge and surface properties of the protein decide how the protein partitions in the system. The nature of the phase components, the MW of the polymer, and the concentration and type of salt used also affect the distribution. ... 

One of the best characterized systems involves mixtures of dextran and polyethyleneglycol (PEG). In such a system, biological substances ranging from soluble proteins to particulate materials (cells or organelles) will partition preferentially in one of the phases. In order to characterize the separation of a substance of interest in an aqueous two-phase system, it is convenient to define a partition coefficient as the ratio of this substance s relevant property in the top and bottom phases. For example, for a protein with biological activity ... 

Different types of Amberlite XAD resins with unique physical and chemical properties have been available. Their use for adsorption of polar organic molecules directly out of biological samples has been demonstrated with pharmaceuticals [263], plant nucleotides [264], plant growth hormones [265], and various steroids [262,268]. In the last case, ample evidence is now available that the use of these resins causes substantially better recoveries of more polar steroid metabolites [262,268] than the previously employed solvent extractions. Setchell et al. [262] used the organic resins and modified dextranes for a complete fractionation of urinary steroid conjugates. Their general procedure (Fig. 3.15) involves the initial sample adsorption and several... 

Hehre, H., Hamilton, D.M., 1949, Bacterial conversion of dextrin into a polysaccharide with the serological properties of dextran. Proceedings of the Societyfor Experimental Biology and Medicine, 71 336-339... 

Rebizak, R., Schaefer, M. and Dellacherie, E., 1998, Polymeric conjugates of Gd diethylenetriamine pentaacetic acid and dextran 2. Influence of spacer arm length and conjugate molecular mass on the paramagnetic properties and some biological parameters. Bioconjug. Chem., 9 94-99... 

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