Measuring apoptosis is essential for understanding the cell death process, especially in cancer research, drug testing, and disease research. Here are several common kits for measuring apoptosis, each of them focusing on a different apoptosis marker:
1. Annexin V/Propidium Iodide (PI) Staining Kit
Mainly used to detect early and late apoptosis. The working principle of this type of kit is that Annexin V binds to phosphatidylserine, which is transferred to the cell surface in early apoptosis, and propidium iodide (PI) can identify necrotic or late apoptotic cells with damaged membrane integrity. The advantage of this type of kit is that it can be widely used in flow cytometry to distinguish between live cells, apoptotic cells, and necrotic cells. The purpose of this type of kit is to stain cells with Annexin V and PI, and then analyze them by flow cytometry or fluorescence microscopy.
2. Caspase Activity Assay Kit
Mainly used to measure the activity of caspase, the core enzyme in the apoptosis process. Caspase-3, -8, and -9 are usually evaluated using fluorescent or colorimetric substrates that release detectable signals when cleaved by active caspases. The advantage of this type of kit is that it is quantitative and sensitive, providing insight into the initiation and execution of apoptosis at the molecular level. The purpose of this type of kit is to incubate cells or lysates with caspase-specific substrates and measure the signal using a microplate reader.
3. TUNEL assay (terminal deoxynucleotidyl transferase dUTP nick end labeling)
It is mainly used to detect DNA fragmentation, which is a hallmark of late apoptosis. It labels the free 3'-OH end of fragmented DNA with a fluorescent or colorimetric marker. The advantage of this type of kit is that it is very sensitive to in situ detection of DNA fragmentation and is often used for tissue samples or adherent cells. The method of using this type of kit is to fix the cells or tissues, then incorporate the labeled dUTP into the fragmented DNA, and finally detect it using a fluorescent or colorimetric method.
References
[1] Maojuan Guo et al., Cell Cycle 2021; 20: 1033-40 (doi: 10.1080/15384101.2021.1919830)
[2] Sabrina Spencer and Peter Sorger 2011; 144: 926-39 (DOI: 10.1016/j.cell.2011.03.002)