Smartphone-assisted quantitative colorimetric identification of thrombin based on peroxidase mimetic features of fibrinogen-gold nanozymes.

Abstract

Fibrinogen-modified gold nanoparticles (Fib-AuNPs) and 3,3',5,5'-tetramethylbenzidine (TMB) substrate besides hydrogen peroxide (H2O2) were applied for assessmentof the biomarker thrombin. Fib-AuNPs have catalytic active sites for the oxidation of TMB besides H2O2 and cause the color change of the substrate. Moreover, they can lead to the enhancement in the absorption wavelengths of 650 and 370nm. By the addition of thrombin to Fib-AuNPs, fibrinogen turns into fibrin, and AuNPs are surrounded by fibrin. Therefore, their active catalytic sites for the oxidation of TMB besides H2O2 are covered by fibrin and cannot cause color change and absorption increase as before. The relationship between the average variations of the color intensity and changes in the absorption wavelengths at 650 and 350nm with different concentrations of bovine thrombin added to Fib-AuNPs was studied. In such manner, three sensitive colorimetric approaches have been developedfor the identification of bovine thrombin with the linear range of 20-120pM and the limit of detection (LOD) of 17.54pM for the average color intensity (G + B), the linear range of 20-120pM and the LOD of 13.41pM for the absorption peak at 650nm, and the linear range of 40-140pM with the LOD of 18.85pM for absorption peak at 370nm. The practical application of this biosensing platform was indicated through the successful determination of bovine thrombin in bovine serum. The satisfactory RSD ( < 10%) and recovery values (99.11-107.61%) confirmed the feasibility of the fabricated sensor.