Near-infrared fluorescence nanoprobe for enzyme-substrate system sensing and in vitro imaging

Herein we report a simple and sensitive fluorescent sensing platform for phenol and enzyme activity detection based on 3-aminobenzeneboronic acid functionalized CuInS2 QDs (APBA-CuInS2 QDs). APBA were covalently linked to CuInS2 QDs surface to form the APBA-CuInS2 QDs which had a fairly symmetric fluorescence emission peak at 736 nm in the near-infrared spectral region. In the presence of tyrosinase, phenol can be catalyzed the oxidization into catechol, which could reactive toward the boronic acid functional groups of APBA-CuInS2 QDs to form five-membered cyclic esters, leading to the fluorescence quenching of the QDs. The effective fluorescence quenching of APBA-CuInS2 QDs by phenol enabled this proposed nanosensor to sensitively detect the phenol product-related enzyme system, such as acid phosphatase-catalyzed hydrolysis of phenyl phosphate. Thus, the proposed biosensor was utilized for facile, sensitive, and selective detection phenol, tyrosinase and acid phosphatase. The detection limits of phenol, tyrosinase and acid phosphatase reached 0.05 μmol L(-1), 0.03 U mL(-1) and 6 nU mL(-1) for, respectively. The feasibility of the proposed nanosensor in real samples assay was also studied and satisfactory results were obtained. Meanwhile, using the APBA-CuInS2 QDs fluorescence probe, we successfully performed in vitro imaging of human prostate cancer cells, suggesting the biocompatible sensor has potentially extensive application clinic diagnoses assays.