Dextran sulfate is a chemically modified, polyanionic derivative of dextran, a branched bacterial polysaccharide, widely utilized for its charge-based interactions in biomedical and research applications. 

Molecular Structure

Dextran sulfate is derived from dextran, a D-glucose polymer composed of approximately 95% α-(1→6) linear backbone linkages and 5% α-(1→3) branch points. Chemical sulfation is achieved through esterification with chlorosulfonic acid, introducing on average ~2.3 sulfate groups per glucosyl residue, corresponding to a sulfur content of approximately 16–20%. The polymer retains the native branched architecture of dextran, with molecular weights typically ranging from 5 to 500 kDa depending on fractionation, and exhibits moderate polydispersity (Mw/Mn ≈ 1.5–2.0). The introduction of sulfate esters confers a high density of negative charges uniformly distributed along the polymer chains.

Synthesis and Physicochemical Properties

Dextran sulfate is produced by partial hydrolysis of Leuconostoc mesenteroides-derived dextran, followed by controlled sulfation under mild reaction conditions and subsequent purification by ethanol precipitation and size-exclusion fractionation. The resulting polymer forms stable, clear aqueous solutions over a pH range of approximately 5 to 7.5. Its strong polyelectrolyte character leads to full chain extension in low-ionic-strength media due to electrostatic repulsion between sulfate groups, yielding a higher hydrodynamic volume than native dextran, while elevated salt concentrations induce chain contraction. The polymer exhibits pH-dependent swelling behavior associated with titratable sulfate groups, limited solubility in the presence of divalent cations such as calcium, and susceptibility to acid-catalyzed hydrolysis. Dextran sulfate is characterized by high solution viscosity, pronounced charge-dependent interactions, and generally favorable biocompatibility with low intrinsic toxicity.