Hydroxyethyl starch (HES) is a non-ionic starch derivative that can be of varying molecular weight. HES is also known as HAES, Tetrastarch (Voluven TM), pentastarch (Pentastan TM) and Hetastarch (Hespan TM). HES has found a use to treat hypovolemia or sudden blood loss. Starch is a naturally abundant (1-4 β)-Glucose polymer that is insoluble in water. However, when functionalised with hydroxyethyl groups, the starch chain becomes water-soluble and has become a useful tool in life sciences. Fluorescein-HES (FHES) is used in studies to evaluate the function and behavior of either HES or a biological system (e g the circulatory system, kidneys etc), or to measure blood volume.
FITC-HES (Fluorescein isothiocyanate hydroxyethyl starch) (FHES) is manufactured by reacting FITC with HES. The product is carefully purified from reagents, solvents and by-products. It is supplied as an orange to dark orange powder which is readily soluble in water and DMSO. Concentrations up to 1 g per 10 mL water is possible without issues but the solution might be viscous. The mean average molecular weight is approx. 165 kDa. The actual molecular weight is measured by gel permeation chromatography (GPC). The degree of FITC substitution lies between 0.001 and 0.01. It is stable when stored in well-sealed containers at room temperature in the dark. FITC-HES has an Absmax of 493 nm and an Emmax of 520 nm. The hydroxyethyl content is on average 0.5 hydroxyethyl groups per Glucose unit.