Colorimetric platform for visual detection of cancer biomarker based on intrinsic peroxidase activity of graphene oxide

A new colorimetric immunoassay for the detection of cancer biomarker prostate specific antigen (PSA) was developed based on the intrinsic peroxidase activity of graphene oxide (GO). GO can catalyze the reaction of hydroquinone in the presence of H2O2 to produce a brown color solution. Secondary antibody (Ab2) functionalized GO (GO-Ab2) was used as label for the immunoassay, while magnetic bead (MB) was selected to immobilize primary anti-PSA antibody (Ab1). In the presence of PSA, an immunocomplex, sandwiching the antigen protein, is formed between the GO-Ab2 and MB-Ab1. With the separation of the immunocomplex using an external magnetic field, different amounts of GO-Ab2 in the solution were mixed with hydroquinone and H2O2 solution and displaying colors. Different colors corresponding to different concentrations of PSA can be directly detected with eyes. Such a simple immunoassay holds great potential as sensitive, selective and point-of-care (POC) tool for clinical diagnosis of cancer biomarkers.