Aptamer-gold nanoparticle-based colorimetric assay for the sensitive detection of thrombin

Herein, we report a sensitive and selective detection method for thrombin based upon oligonucleotide-functionalized gold nanoparticle probes that can combine with the thrombins by van der Waals force, where the thrombin molecule acts as a bridge to link the monodispersed aptamer-modified gold nanoparticles together, since thrombin includes two binding sites for the aptamer. This leads to the visible color changes from wine-red to blue-purple, which relies upon the distance-dependent optical properties of gold nanoparticles. The concentration can be determined by monitoring with naked eye or a UV–vis spectrometer. In addition, this assay does not utilize any organic cosolvents, heavy metal ion, enzymatic reactions, light-sensitive dye molecules, lengthy protocols, or sophisticated instrumentation, thereby overcoming some limitations of more conventional methods. Moreover, thrombin at concentrations as low as 5 pM (1.679 ng/mL) can be detected in this assay with a colorimetric format.