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

Abstract

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 × 10⁻¹¹ to 3.9 × 10⁻⁷ mol L⁻¹ with a detection limit (LOD) of about 8.7 × 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.