Protease viability marker assay is based on the principle that protease activity is rapidly lost when cells die. Advantages of protease viability marker assay include: 

• It is relatively nontoxic to cells in culture. 
• There is little change in the viability of cells on long-term exposure of the GF-AFC substrate. 
• It has a short incubation time of about 30 minutes to 60 minutes. 
• Cell population remains viable at the end of the protease viability marker assay and can be used for subsequent assays, making this assay suitable for multiplexing with other assays.