Hello Debalina Das

Yes, you may.

Generally, after adding MTT, the plate is incubated for approximately 2-4 hours at 37-degree C. The cells are viewed periodically for the appearance of intracellular precipitate using an inverted microscope. Even after 4 hours, you don’t observe the formation of formazan crystals, you may keep it for a longer incubation time up to 24 hours. Sometimes, depending upon the cell type and experimental conditions you may have to extend the incubation period with MTT.

The purple formazan crystals are solubilised using solubilizing solution and incubated in the dark at room temperature (18-24 deg C) for 2 hours. If the readings are low and there are crystals remaining, you may incubate the plate for a longer period. The solubilization time may be shortened by incubating the plate at 37-degree C.

Best.

While you hopefully can, be mindful of how you will distinguish after 17 hours if the cytotoxic effect is due to your cisplatin treatment or due to MTT reagent, which by the way also has its own cytotoxic effects as reported in the literature. You just have to be strategic in terms of what controls you will use. However, if you have time and resources, try performing ATP assay for cell viability.

Hammad Mufti is right. MTT is cytotoxic. Check out on why the cells are not able to reduce MTT within 4 hours. Maybe the culture conditions that alter the metabolism of cells could be affecting the rate of MTT reduction.