Dextran is a polymer of anhydroglucose. It is composed of approximately 95% alpha-D-(166) linkages. The remaining (163) linkages account for the branching of dextran. Conflicting data on the branch lengths implies that the average branch length is less than three glucose units. However, other methods indicate branches of greater than 50 glucose units exist. Native dextran has been found to have a molecular weight (MW) in the range of 9 million to 500 million. Lower MW dextrans will exhibit slightly less branching and have a more narrow range of MW distribution. Dextrans with MW greater than 10,000 behave as if they are highly branched. As the MW increases, dextran molecules attain greater symmetry. Dextrans with MW of 2,000 to 10,000, exhibit the properties of an expandable coil. At MW below 2,000, dextran is more rod-like. The MW of dextran is measured by one or more of the following methods: low angle laser light scattering, size exclusion chromatography, copper-complexation and anthrone reagent colorometric reducing-end sugar determination and viscosity.
FITC-dextran is used in cardiovascular, microcirculation, perfusion, cell monolayer and cell membrane permeability research as fluorescent flux tracer compound that supports the measurement of processes such as blood flow, membrane damage, vascular drainage and renal elimination. Small FITC-dextrans are also used to measure processes such as endocytosis. Fluorescein-dextran, 40 kDa, may be used for the study of cell endocytic activity. FITC-dextran-40 may be used to study endothelial monolayer porosity and apical-basolateral movements within cell layers.
FITC-dextran is used extensively in microcirculation and cell permeability research utilizing microfluorimetry. FITC-dextran has been used to study plant cell wall porosity and capillary permeability. Plasma proteins have been shown not to bind to FITC-dextran.
Dextran labeled with fluorescein isothiocyanate for possible use in perfusion studies in animals.
Sigma typically tests the solubility of FITC dextrans in water at concentrations at or above 25 mg/ml. Solutions should be protected from light. In vivo, FITC-dextran is stable for more than 24 hours.