An origami paper-based electrochemical immunoassay for theC-reactive protein using a screen-printed carbon electrode modified with graphene and gold nanoparticles

An origami paper-based electrochemical immunoassay for C-reactive protein (CRP) detection is described. The assay integrates multiple steps of electrode modification into a single device. A graphene-modified screen-printed carbon electrode (G/SPCE) was employed to enhance sensitivity. Gold nanoparticles were first electrodeposited onto the G/SPCE, followed by a self-assembled monolayer of L-cysteine. The capture anti-CRP was then covalently immobilized on the modified electrode. CRP was quantified by measuring the changes in the charge-transfer resistance of the electrode by using hexacyanoferrate as the redox probe. Cyclic voltammetry and scanning electron microscopy were also applied to verify the successful modification of the electrode. Under optimal conditions, impedance increase in the 0.05-100gmL(-1) CRP concentration range, and the limit of detection is 15ngmL(-1) (at S/N=3). The immunoassay was successfully applied to the determination of CRP in a certified human serum sample. This method is simple, low-cost, portable and disposable.