Dextran is a branched polysaccharide composed of D-glucose units, predominantly linked by α-1,6 glycosidic bonds and produced through bacterial fermentation of sucrose. 

Molecular Structure

Dextran consists of a linear backbone of α-D-(1→6)-linked glucopyranose residues with approximately 5% branching via α-(1→3) glycosidic linkages. Branch lengths vary significantly, ranging from 1–2 glucose units to more than 50 units depending on the bacterial source and fractionation process. Dextran exhibits a wide molecular weight distribution, spanning from approximately 1 kDa to over 2,000 kDa. 

Production and Properties

Dextran is synthesized enzymatically by bacteria, most notably Leuconostoc mesenteroides NRRL B-512(F), through the action of dextransucrase, which hydrolyzes sucrose and transfers glucose units to the growing polymer chain. The resulting polysaccharide demonstrates excellent water solubility over a wide pH range, low immunogenicity, and biodegradability via dextranase enzymes. Dextran solutions exhibit high viscosity that increases with polymer concentration and molecular weight, forming stable and transparent coils suitable for osmotic regulation and stabilization purposes. Additional functional properties include metal chelation, protein stabilization, and electrolyte compatibility, although dextran remains insoluble in alcohols and certain ketones.

Biomedical Applications

Dextran is widely used as a plasma volume expander, such as Dextran 40 or Dextran 70, in the management of hypovolemic shock, where it improves blood flow while minimizing coagulation risks due to its favorable biocompatibility profile. In drug delivery systems, dextran is employed in polymer–drug conjugates for targeted chemotherapy and in nanoparticle formulations for gene therapy, leveraging its non-toxicity and enzymatic degradability. Dextran is also used to coat iron oxide nanoparticles for magnetic resonance imaging (MRI) contrast agents. In tissue engineering, dextran-based hydrogels and cryoprotectants support cell preservation and scaffold formation. Additionally, dextran derivatives such as Sephadex are extensively utilized as chromatography matrices for size-exclusion-based purification of biomolecules.