Magnetic graphene oxide-supported hemin as peroxidase probe for sensitive detection of thiols in extracts of cancer cells.

Magnetic graphene oxide (GO)-hemin probes containing disulfide bonds are simply and effectively synthesized through amide reaction to covalently link magnetic particles to GO surface and π-π stacking interaction between hemin and GO to immobilize hemin on GO. Based on the strong nucleophilicity of sulfhydry, we have developed a colorimetric detection system for thiols by using glutathione (GSH) as a model analyte. Upon the introduction of GSH to the fabricated magnetic particle (MP)-GO-hemin probes, the disulfides can be readily reduced by thiols, resulting in the release of GO-hemin hybrids to solution. Due to the existence of hemin on GO surface, the released GO-hemin that has the intrinsic peroxidase-like activity can catalyze the oxidation of ABTS(2-) by H2O2 to form the colored radical product ABTS(·-). A broad linear dynamic range of 10(-10) M to 10(-6) M GSH is achieved with a detection limit of 8.2×10(-11) M (3σ). Moreover, the new probe is successfully applied to the detection of non-protein thiols and protein thiols in the extracts of Ramos cells, which shows favorable correlationship with the results obtained by electrochemical method. In addition, the MP-GO-hemin probe can detect non-protein thiols in Ramos extracts as low as 500 cells. In this assay, the prepared MP-GO-hemin conjugates are thoroughly characterized by SEM, AFM, UV-Vis, FT-IR, and Raman spectroscopy.