DQ-BSA-RED is a red-fluorescently labeled bovine serum albumin derivative specifically designed to monitor lysosomal proteolytic activity. DQ-BSA-RED exhibits excitation and emission maxima at 590 nm and 620 nm, respectively, and contains multiple dye moieties resulting in fluorescence self-quenching until proteolytic cleavage occurs within lysosomes, upon which bright fluorescence is emitted. DQ-BSA-RED therefore enables the visualization and quantification of lysosomal functionality in live-cell assays, while inactive lysosomes fail to generate fluorescence, providing a valuable tool for studying autophagy and intracellular degradation processes.

DQ-BSA-RED Usage Protocol (The following protocol is for reference only and should be modified according to your specific experiments.)
1. Stock solution preparation: Prepare a 1 mg/mL stock solution using ddH2O. It is recommended to aliquot and store at -80°C in the dark.
2. Working solution preparation: Dilute the stock solution with cell culture medium to prepare a 10 μg/mL working solution, which should be freshly prepared before use. Note: The working solution concentration can be adjusted according to actual experimental conditions.
3. Cell staining and imaging:
3.1 Add the staining working solution at a concentration of 10 μg/mL to the cell culture medium.
3.2 Incubate the cells at room temperature for 6–12 hours.
3.3 After aspirating and discarding the dye working solution from the medium, observe under a fluorescence microscope (excitation/emission wavelength = 561 nm/595 nm).
Note: Before adding the staining working solution, ensure that the lysosomal function in the cells has been disrupted. If lysosomes remain active, DQ-BSA-RED may be degraded during staining, leading to partial chromogenic phenomena.