CDP-Star is a chemiluminescent substrate used primarily in molecular biology and immunological assays. It is commonly employed in nucleic acid detection, such as in Southern blotting, where it enables the visualization of DNA sequences hybridized with labeled probes. The compound is also widely used in Northern blotting for RNA detection.

Its application extends to non-radioactive detection methods, offering a safer alternative to isotopic labeling. When dephosphorylated by alkaline phosphatase, CDP-Star emits light, which can be captured on X-ray film or by digital imaging systems. This makes it highly effective for high-sensitivity detection in membrane-based assays.

Additionally, CDP-Star is utilized in some immunoassays where alkaline phosphatase-conjugated antibodies are used, allowing for the detection of specific proteins in Western blotting and ELISA techniques. Its sustained light emission provides a wide detection window and enhances signal stability, improving quantification accuracy.