Dual-mode colorimetric and homogeneous electrochemical detection of intracellular/extracellular H2O2 based on FeSx/SiO2 nanoparticles with high peroxidase-like activity

Abnormal expression of hydrogen peroxide (H2O2) elucidates cell dysfunctions and might induce the occurrence and deterioration of various diseases. However, limited by its ultralow level under pathophysiological conditions, intracellular and extracellular H2O2 was difficult to be detected accurately. Herein, a colorimetric and homogeneous electrochemical dual-mode biosensing platform was constructed for intracellular/extracellular H2O2 detection based on FeSx/SiO2 nanoparticles (FeSx/SiO2 NPs) with high peroxidase-like activity. In this design, FeSx/SiO2 NPs were synthesized with excellent catalytic activity and stability compared to natural enzymes, which improved the sensitivity and stability of sensing strategy. 3,3',5,5'-Tetramethylbenzidine (TMB), as a multifunctional indicator, was oxidized in the presence of H2O2, generated color changes and realized visual analysis. In this process, the characteristic peak current of TMB decreased, which could realize the ultrasensitive detection of H2O2 by homogeneous electrochemistry. Accordingly, by integrating visual analysis ability of colorimetry and the high sensitivity of homogeneous electrochemistry, the dual-mode biosensing platform exhibited high accuracy, sensitivity and reliability. The detection limits of H2O2 were 0.2 μM (S/N = 3) for the colorimetric method and 2.5 nM (S/N = 3) for the homogeneous electrochemistry assay. Therefore, the dual-mode biosensing platform provided a new opportunity for highly accurate and sensitive detection of intracellular/extracellular H2O2.