Colorimetric Detection of Thrombin Based on Intensity of Gold Nanoparticle Oligomers with Dark-Field Microscope

Abstract

We develop a simple but efficient assay platform for thrombin detection with ultrahigh sensitivity, which is based on intensity of gold nanoparticle (AuNP) oligomers as an optical readout mode. Capture of the two aptamers to the same thrombin molecule induces the hybridization between the two aptamers and thereby brings the AuNPs linked at one end of one aptamer to close proximity to those linked at one end of the other aptamer, forming AuNP oligomers. By measuring the intensity of yellow and red dots (AuNP oligomers) on a dark-field image, target thrombin concentration can be accurately determined. The limit of detection (LOD) of thrombin was obtained as low as 5 fM, with a wide linear range of 13 fM–0.13 nM. Moreover, the approach was used for thrombin detection in serum samples through the standard addition, and thrombin concentration in serum samples was also determined. In view of the simplicity and effectivity of the method, the sensing strategy can thus be applied for disease diagnosis.