FITC-Dextran (MW 10000) is a marker consisting of coupling fluorescein-isothiocyanate to dextran (10 kDa). FITC-Dextran are polysaccharides comprised of varying lengths of branched glucose molecules and can be used to determine solute, ion and protein permeability of the blood-brain barrier (BBB) based on the size of the dextran used.