Ultrasensitive quantification of dextran sulfate by a mix-and-read fluorescent probe assay

Dextran sulfate is semi-synthetic, polydisperse sulfated polysaccharide with important applications in clinical practice, in the manufacturing of plasma derived protein therapeutics and in biomedical research. The sensitive detection of dextran sulfate is relevant to preclinical and clinical drug development projects, the quality control of pharmaceutic formulations, and the process control in plasma fractionation using dextran sulfate modified chromatographic columns. Most analytical methods for the sensitive detection of dextran sulfate require multistep protcols and have not been transferred into commercial formats. We describe here the direct quantification of dextran sulfate using the commercially available molecular probe Heparin Red, by a simple mix-and-read fluorescence assay. With a sensitive benchtop fluorimeter, a quantification limit of 310 pg/mL dextran sulfate is achieved. This is superior by at least one order of magnitude to the quantification or detection limit of other reported methods. The outstanding simplicity and sensitivity establish Heparin Red as a new analytical tool for the determination of dextran sulfate.