Following the initial studies, where the probe MQ-CN-BTZ displayed high selectivity and sensitivity towards NADH, we further attempted to establish the intracellular NADH detection potential of the probe in HepG2 cellular model. For this, the probe's cytotoxicity was evaluated using the MTT assay. In this assay, the yellow colored tetrazolium dye gets reduced to formazan (purple crystal) in the presence of intracellular enzymes. The formation of purple formazan crystals indicate the percentage of the cell viability by measuring the absorbance of the formed formazan crystals at 570 nm. The results demonstrated that more than 80% of the cells were viable even at 15 μM concentration of the probe, indicating low cytotoxicity of the probe.