Colorimetric thrombin assay using aptamer-functionalized gold nanoparticles acting as a peroxidase mimetic

The article describes a method for the determination of thrombin that is based on the use of gold nanoparticles (AuNPs) functionalized with an aptamer labeled with a horseradish peroxidase mimick. The assay is based on (a) the high affinity between aptamer and thrombin, and (b) on the finding that AuNPs display HRP-like properties in catalyzing the oxidation of 3,3,5,5-tetramethylbenzidine to give a blue reaction product with an absorption maximum at 652 nm. The limit of detection for thrombin is as low as 0.02 pM, and the analytical range extends from 0.1 pM to 0.1 mu M thrombin. The aptamer-based assay was successfully applied to the quantitation of thrombin in spiked human serum. This method is simple, inexpensive and highly sensitive.