FITC-Dextran (MW 40000) is a kind of dextran fluorescent probe labeled with fluorescein isothiocyanate (FITC) (Ex=495 nm; Em=525 nm). FITC-Dextran (MW 400000) can be used as a tracer marker to reveal heat shock-induced cell injury and detect the early and late stages of apoptosis. In addition, this probe can be used in the study of cell permeability, including the permeability of the blood-brain barrier and the quantitative analysis of its damage degree.

Cell Labeling [1]
This method is applicable to apoptotic HeLa cells and human peripheral blood mononuclear cells (PBMCs), while viable HeLa cells and PBMCs are not stained by FITC-Dextran.
1. Apoptosis was induced by incubation at 43.5 °C for 1 h and at 37 °C for 8 h.
2. Cells were resuspended in 100 μL of culture medium and mixed with 10 μL of propidium iodide (PI) and 10 μL of FITC-Dextran (MW 40000) in Q-prep tubes, resulting in final concentrations of 7.5 μM for PI and 1.13 μM for FITC-Dextran, respectively.
3. Cells were incubated at room temperature in the dark for 25 min.
4. 3 mL of the labeled cell culture medium was collected and centrifuged at 500 g for 10 min.
5. The centrifuged cells were harvested, resuspended in 1 mL of culture medium, and analyzed by flow cytometry or fluorescence microscopy (PI: Ex=500 nm, Em=600 nm; FITC-Dextran (MW 40000): Ex=495 nm, Em=525 nm).
Paracellular Permeability Assay [4]
1. FITC-Dextran was added to the basal medium of Transwell chambers at a final concentration of 0.1 mg/mL.
2. Culture medium was collected from the Transwell inserts after incubation for 15 min.
3. Fluorescence signals were measured (Ex=485 nm, Em=538 nm).
4. The concentration of FITC-Dextran was calculated based on fluorescence intensity.
5. Permeability was calculated from the concentration results.

Intestinal Barrier Function Assay [5]
1. Mice were subjected to 4 hours of starvation treatment.
2. FITC-Dextran (MW 40000) was used for intragastric gavage in mice at a dose of 0.6 mg/g.
3. Within 4 hours after gavage, the fluorescence intensity was detected and recorded (emission wavelength Em 520 nm).

H2O: 40 mg/mL, Sonication is recommended.