A novel smartphone-based electrochemical cell sensor for evaluating the toxicity of heavy metal ions Cd 2+ , Hg 2+ , and Pb 2+ in rice

A novel smartphone-based electrochemical cell sensor was developed to evaluate the toxicity of heavy metal ions, such as cadmium (Cd 2+ ), lead (Pb 2+ ), and mercury (Hg 2+ ) ions on Hep G2 cells. The cell sensor was fabricated with reduced graphene oxide (RGO)/molybdenum sulfide (MoS 2 ) composites to greatly improve the biological adaptability and amplify the electrochemical signals. Differential pulse voltammetry (DPV) was employed to measure the electrical signals induced by the toxicity of heavy metal ions. The results showed that Cd 2+ , Hg 2+ , and Pb 2+ significantly reduced the viability of Hep G2 cells in a dose-dependent manner. The IC 50 values obtained by this method were 49.83, 36.94, and 733.90 μM, respectively. A synergistic effect was observed between Cd 2+ and Pb 2+ and between Hg 2+ and Pb 2+ , and an antagonistic effect was observed between Cd 2+ and Hg 2+ , and an antagonistic effect at low doses and an additive effect at high doses were found in the ternary mixtures of Cd 2+ , Hg 2+ , and Pb 2+ . These electrochemical results were confirmed via MTT assay, SEM and TEM observation, and flow cytometry. Therefore, this new electrochemical cell sensor provided a more convenient, sensitive, and flexible toxicity assessment strategy than traditional cytotoxicity assessment methods. Graphical abstract