Sandwich electrochemical thrombin assay using a glassy carbon electrode modified with nitrogen- and sulfur-doped graphene oxide and gold nanoparticles.

Graphene oxide doped with nitrogen and sulfur was decorated with gold nanoparticles (AuNP-SN-GO) and applied as a substrate to modify a glassy carbon electrode (GCE). An aptamer against the model protein thrombin was self-assembled on the modified GCE which then was exposed to thrombin. Following aptamer-thrombin interaction, biotin-labeled DNA and aptamer 2 are immobilized on another AuNP-SN-GO hybrid and then are reacted with the thrombin/AuNP-SN-GO/GCE to form a sandwich. The enzyme label horseradish peroxidase (HRP) was then attached to the electrode by biotin-avidin interaction. HRP catalyzes the oxidation of hydroquinone by hydrogen peroxide. This generates a strong electrochemical signal that increases linearly with the logarithm of thrombin concentration in the range from 1.0 × 10-13 M to 1.0 × 10-8 M with a detection limit of 2.5 × 10-14 M (S/N = 3). The assay is highly selective. It provides a promising strategy for signal amplification. In our perception, it has a large potential for sensitive and selective detection of analytes for which appropriate aptamers are available. Graphic abstract A sandwich-type electrochemical aptasensor is fabricated for detection of thrombin using a glassy carbon electrode modified with nitrogen- and sulfur-doped graphene oxide and gold nanoparticles.