FITC-dextran (MW 4000) is a fluorescein isothiocyanate (FITC) Dextran fluorescent probe (Ex=495 nm; Em=525 nm). FITC-Dextran (MW 4000) can be used as a marker to reveal cell damage caused by heat shock and to study the early and late stages of apoptosis. FITC-Dextran (MW 4000) can also be used for cell permeability studies, such as the determination of blood-brain barrier permeability and the degree of blood-brain barrier disruption.