Dextran group

In the mid-1930s, Stacey became interested in the dextran group of polysaccharides, which became one of his enthusiasms and successes. It combined his chemical and commercial interests and allied them with the idealistic side of his nature to help those suffering from injury or disease. 

Conjugation of a 2-nitroimidazole derivative to carboxymethyl dextran allowed doxorubicin-loading with hypoxia-induced cellular uptake and cytotoxicity in vitro [110]. The dextran group for stability in the circulation and primary tumor accumulation was combined with conversion from a hydrophobic 2-nitroimidazole to a hydrophilic 2-aminoimidazole under hypoxia to promote doxorubicin release in tumor environment. This system showed a 4-fold doxorubicin accumulation in tumor over liver, lung, spleen, kidney, and heart 24 h after systemic injection and enhanced anticancer activity in vivo over free drug. 

Sephadex A trade name for an insoluble hydrophilic substance prepared by cross-linking dextran, and used in gel filtration. It can also be linked to acidic or basic groups for ion exchange or to alkanes for the chromatography of lipophilic compounds. 

Dextran can be produced in a range of molecular weights and crossed-linked or substituted with a variety of functional groups. These products (Sephadex) are routinely used in the purification of proteins and pharmaceutical and other medically important compounds. 

It is perhaps ironic that, many years after his interest was first aroused, Stacey was to experience a fermentation failure owing to an unwanted dextran. He, and a large group of colleagues (potential co-tasters ), published a report of an attempt to make elderberry wine. A viscous, transparent gum, rather than a delicious drink, was produced. The gum was a typical, but unwelcome, dextran. 

PGIP, purified fi om P.vulgaris hypocotyls [11], was immobilized to the sensor ch via amine coupling. A continuous flow of HBS buffer (5 pl/min) was mantained over the sensor surface. The carboxylated dextran matrix of the sensor surface was first activated by a 6-min injection of a mixture of N-hydroxy-succinimide and N-ethyl-N - (3-diethylaminopropyl) carbodiimide, followed by a 7-min injection of PGIP (lOng/pl in 10 mM acetate, pH 5.0). Hie immobilization procedure was con leted by a 7-min injection of 1 M ethanolamine hydrochloride to block the remaining ester groups. 

The sensor ch consists of a glass de on to which a SO-nm thick gold film has been deposited. The gold film is then covered with a linker-layer to which a matrix of carboxylated dextran is attached. The dextran, which extends typically 100 nm out fi om the sur6ce, provides a hydrophilic, activatable and flexible polymer to which biomolecules can be coupled throu amine, sulphydryl, carboxyl and other groups. 

Solubility generally decreases with increase in chain size and extent of branching. The solubility of dextran can be divided into four groups — those that are readily soluble at room temperature in water, IMF, DMSO and dilute base those that have difficulty dissolving in water those that are soluble in aqueous solution only in the presence of base and, those that are soluble only under pressure, at high temperatures (> 100°C) and in the presence of base. Dextran B-512 readily dissolves in water and 6M, 2M glycine and 50% glucose aqueous solutions. 

A suitable degree of esterification of dextran with butyric or palmitic acid is achieved by CDI in formamide or DMSO. In the absence of carboxylic acids dextran can be converted by CDI into a crosslinked product with intrachain as well as interchain carbonate links. Such carbonate links permit drugs containing hydroxyl groups to be coupled to the dextran.[174]... 

The presence of three hydroxyl groups per glucose unit was shown by the preparation of a triacetate and a tribenzoate. Six or seven methyla-tions (using dimethyl sulfate and concentrated alkali) of dextran did not raise the methoxyl content above 41% (theoretical maximum 45.6%). Also, Purdie methylations (using methyl iodide and silver oxide) and methylation with thallium ethoxide and methyl iodide were ineffective in raising the methoxyl content of methylated dextran above 43.5%. The maximum theoretical methoxyl content was eventually attained by modified Muskat methylations. 6 Partially methylated dextran suspended in anisole solution was treated with sodium in liquid ammonia, and the sodium salt of methylated dextran thus formed was allowed to react with methyl iodide. The methoxyl content of the partially methylated dextran was raised by three such methylations from 42% to 45.5% and by five such methylations from 30% to 45.4%. 

The supports employed for covalent attachment of enzymes can be classified into two groups a) natural (agarose, dextran, cellulose, porous glass, silica, the optical fiber itself or alumina) and b) synthetic (acrylamide-... 

SPR chips coated with a carboxymethyl dextran matrix are supplied commercially by Biacore, a leading manufacturer of SPR instruments. Similar technique can be used for preparation of carboxymethyl dextran matrix on Me(Si)Ox surfaces on which -OH groups are generated by reaction with 3-glycidoxypropyltrimethoxysilane13. 

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