The application of the novel pH probe in measuring cell colony’s pH variations and their comparison d with cell viability and ROS generation in a TiO2 NP-induced cytotoxicity model. Green plots are pH measurement using our developed probe, blue and red plots are data are the cell viability and ROS kits measurements. Three NP concentration, 50, 100 and 150 μg/mL, were used is this study. Values are mean ± SD (n≥3). Statistical significance was indicated by *p < 0.05 (significant), and ** p < 0.01 (very significant), versus the control groups.