EF-5 is primarily used in biomedical research as a hypoxia marker. It helps in identifying and measuring low oxygen levels (hypoxia) in tissues, which is crucial for studying conditions like cancer, stroke, and cardiovascular diseases. Researchers administer EF-5 to cells or animal models, where it selectively binds to hypoxic regions. By using techniques like fluorescence microscopy or immunohistochemistry, scientists can visualize and quantify these areas, aiding in the understanding of disease progression and the development of targeted therapies. Its application is particularly valuable in oncology for assessing tumor hypoxia, which influences treatment resistance and patient outcomes.