Synthesis and structure

CM-dextrans are manufactured by reacting selected dextran fractions with an activated carboxymethyl derivative in alkali. This leads to the introduction of O-carboxymethyl groups along the dextran chain. The carboxyl content is approximately 5% which is equivalent to about one CM group for every 5 five glucose units. Higher degrees of substitution may be achieved if required. The dextran used is elaborated by Leuconostoc mesenteroides B512F and is essentially a linear α (1-6)-linked glucose chain with a low percentage(2-5%) of α(1-3) branches distributed along the chain. The dextran fractions used have weight average molecular weights (Mw) of 4000 to 2000000 and are carefully controlled by GPC, optical rotation, absorbance and loss on drying.

Physical properties

Carboxymethyl dextran (CM-dextran) is a white, odourless and tasteless powder which is freely soluble in water or electrolyte solutions. The product has a pronounced polyanionic character by virtue of the negatively charged carboxyl groups attached. The solution properties of CM-dextran are described in several publications (1,2). In neutral solutions, the carboxymethyl substituents will repel

each other leading to an expansion of the dextran coil (2). This effect is observed when the products are examined by gel permeation chromatography (GPC) whereby the apparent weight average molecular weight (Mw) is approximately 10% higher than that of the starting dextran. CM-dextrans are insoluble in most organic solvents, for example, ethanol, methanol, acetone, chloroform, ethyl acetate Etc

Applications

Important spheres of research where CM-dextrans are employed are listed below.

1. Carriers of paramagnetic contrast agents. (3-4)

2. Preparation of conjugates of pharmacologically active compounds (5-7)

3. CM-dextrans in biosensors (8-14)

4. CM-dextrans for preparing iron containing nanoparticles (4,15)

5. Many early patents describe uses for CM-dextrans in cosmetic, agricultural, food, paints,

textiles applications

CM-dextran（CM--葡聚糖，羧甲基--dextran，Carboxymethyl-dextran）：

艾美捷CM-dextran#CMD4、CMD10、CMD20等為白色、無臭無味粉末，易溶于水和電解質溶液。羧甲基含量對應于每5個葡萄糖單元約1個CM基團，羧基含量為3 - 7%。

CM-dextran#CMD4、CMD10、CMD20等潛在的應用領域包括：

通過羧基反應結合陽離子（無機和有機）的試劑

化妝品

制劑中的無毒成分

用于敏感生物聚合物的穩定劑

CM-dextran的物理性質：

羧甲基-葡聚糖（CM-dextran）是一種白色、無臭、無味的粉末，可自由釋放可溶于水或電解質溶液。該產品具有明顯的聚陰離子特征由于所連接的帶負電荷的羧基。在中性溶液中，羧甲基取代基會排斥相互作用導致-dextran線圈（2）的膨脹。當產品通過凝膠滲透色譜法（GPC）檢查，由此表觀重量平均值分子量（Mw）比起始-dextran的分子量高約10%。CM-dextran是不溶于大多數有機溶劑，例如乙醇、甲醇、丙酮、氯仿、乙酸乙酯等

CM-dextran的化學性質：

在dextran鏈中插入羧基提供了進一步的固定化機會具有有趣生物活性的分子（藥物、酶、診斷示蹤劑）-dextran。羧基部分可用于許多反應，例如酯化、酰胺化與胺、Ugi或Passerini反應。簡單的離子結合反應也可以提供一系列包含不同陽離子分子的衍生物。

文獻參考：

1. K.Gekko, Solution properties of dextran and its ionic derivatives, ACS Symposium Series, 1981, 150, 415-438;K.Gekko and H.Noguchi, Selective interaction of calcium and , magnesium ions with ionic dextran derivatives, Carbohydr. Res., 1979, 69, 323-326.

2. O.Smidsr?d, Estimation of the relative stiffness of the molecular chain in polyelectrolytes from viscosity measurements at different ionic strengths. Comparison of polycations and polyanions, Acta Chem.Scand., 1971, 25(7) 2770-1.

3. P.Rongved and J.Klaveness, Water soluble polysaccharides as carriers of paramagnetic contrast reagents for magnetic resonance imaging; Synthesis and relaxation properties, Carbohyd.Res., (1991), 214, 315-323.

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5. M.Baudys, D.Letourneur et al., Extending insulin action in vivo by conjugation to carboxymethyl dextran, Bioconj. Chem., 1998, 9,176-183. Y.Ota, P.Oehr et.al., The application of immunotargetting into cancer therapy with carboplatin; in vitro and in vivo studies, Asia Oceania J.Obstet.Gynaecol., 1993, 19(4), 449-457.

6. H.Ma, X.Li et. Ala., High antimetastatic efficacy of MEN4901/T-0128, a novel campothecin carboxymethyldextran conjugate, J.Surg.Res., 2011, 171(2), 684-690.

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