CuInS2 quantum dots as a near-infrared fluorescent probe for detecting thrombin in human serum

This paper describes a novel, simple method for the highly sensitive and selective detection of thrombin using fibrinogen (Fib) and CuInS2 quantum dots (QDs) as biosensing probes. Water-soluble near-infrared CuInS2 QDs capped by mercaptopropionic acid (MPA) were directly synthesized by a hydrothermal method. Addition of fibrinogen to the CuInS2 QDs solution led to the formation of a Fib-CuInS2 QDs complex through electrostatic interactions and hydrogen bonding, and resulting in the enhancement of photoluminescence (PL) intensity and a red shift of the PL peak. Once thrombin was introduced into the Fib-CuInS2 QDs system, it catalyzed the polymerization of the free and conjugated fibrinogen species to form insoluble fibrillar fibrin-CuInS2 QDs agglutinates. After centrifugation, the PL intensity of the supernatants decreased upon increasing the concentration of thrombin. This Fib-CuInS2 QDs probe provided a highly specific selectivity and a linear detection of thrombin in the range of 6.7 x 10(-11) to 3.9 x 10(-7) mol L-1 with a detection limit (LOD) of about 8.7 x 10(-12) mol L-1, and realized the thrombin detection in human serum samples directly. Compared with those obtained by using other nanomaterials and aptamer-based detection methods, this approach provided a lower LOD for thrombin detection. The proposed approach provides a simple and fast-responding procedure, which might hold a promising potential for application in the diagnosis of diseases associated with coagulation abnormalities and cancers.