A novel electrochemiluminescence immunosensor based on Mn doped Ag2S quantum dots probe for laminin detection

In recent years, quantum dots (QDs) have been widely used as biological probes, however, most of the QDs used in electrochemiluminescence (ECL) studies have toxic heavy metals, which was an important road-block for QDs in bio-application. A novel low-toxic, water-dispersed Mn doped Ag2S quantum dots (Ag2S:Mn QDs) were firstly served as a kind of ECL materials, and applied to construct ECL biosensor for the detection of laminin (LN). Here, the Ag2S QDs were simply synthesized with 3-Mercaptopropionic acid (3-MPA) as growth template, and then Mn was doped into Ag2S QDs to improve the optical and electrical properties. Herein, the energy levels and electron transfer path were studied in detail to explain the ECL performance of Ag2S:Mn QDs with K2S2O8 as coreactant. Furthermore, the bovine serum albumin (BSA) containing amino groups (-NH2) could easily combine with Ag2S:Mn QDs via amide bond, and multiple QDs gathered to form a unit (BSA-Ag2S:Mn bioconjugates), which provided mass active area to immobilize antibody and possessed strong ECL emission to improve the detection sensitivity. Based on a sandwiched immunoassay method, this proposed immunosensor achieved a linear range from 10 pg/mL to 100 ng/mL with a relatively low detection limit of 3.2 pg/mL for LN detection. Compared with traditional luminescent reagents, the Ag2S:Mn QDs could be served as a kind of promising luminescent materials for new types of ECL biosensors in the future due to its low toxicity, well photo-stability and easy surface functionalization. (C) 2016 Elsevier B.V. All rights reserved.