Turn-on colorimetric sensor for ultrasensitive detection of thrombin using fibrinogen-gold nanoparticle conjugate

A simple, colorimetric 'turn on' sensor for ultrasensitive detection of thrombin has been developed using fibrinogen-modified gold nanoparticles (Fib-Au NPs). The assay was based on the thrombin-fibrinogen interaction which is part of the physiological process of blood clotting. The fibrinogen was immobilized on the surface of 96-well plate offering reactive N-oxysuccinimide esters (referred to as NOS group) surface. Introducing thrombin and Fib-Au NPs into the fibrinogen-bound 96-well plate induced the immobilization of Fib-Au NPs on the surface of 96-well plate through the thrombin mediated conversion of soluble fibrinogen to insoluble cross-linked fibrin. Such process could be detected visually post HAuCl4-NH2OH redox reaction catalyzed by the Au NPs. The parameters governing the performance of the assay have been optimized. The detection limit was 3.2 fM, corresponding to 0.16 amol thrombin in 50 mu L of sample. Other proteins, such as bovine serum albumin (BSA), pepsin, trypsin, hemoglobin, lysozyme, and cytochrome c did not show interference with the assay of thrombin. In addition, the work demonstrates the feasibility of thrombin detection in a complex matrix, showing potential for rapid medical diagnostics.