Elevated cathepsin enzyme activity in serum or the extracellular matrix can signify a number of pathological conditions. Magic Red Assay Kits are used by researchers seeking to quantitate and monitor cathepsin activity in cultured cells and tissues. This assay kit detects cathepsin L activity.

To use Magic Red, add the substrate directly to the cell culture media, incubate, and analyze. Because it is a cell permeant, it easily penetrates the cell membrane and the membranes of the internal cellular organelles – no lysis or permeabilization steps are required. If cathepsin enzymes are active, the Magic Red substrate is cleaved and the cresyl violet fluorophore will become fluorescent upon excitation. As enzyme activity progresses and more Magic Red substrate is cleaved, the signal will intensify, allowing researchers to watch the color develop over time. Samples can be analyzed by fluorescence microscopy or with a fluorescence plate reader. Hoechst 33342 and Acridine Orange are included in the kit to detect nuclear morphology and lysosomal organelle structure, respectively.

• The staining solution is typically used to stain cells at approximately 1/25 for microscopy analysis or 1/15 for plate reader analysis.