Near-Infrared Electrochemiluminescence Immunoassay with Biocompatible Au Nanoclusters as Tags
Lei Yu, Qiao Zhang, Qi Kang, Bin Zhang, Dazhong Shen, Guizheng Zou
Abstract
The design and development of novel electrochemiluminescence (ECL) systems with near-infrared (NIR) emission beyond 800 nm are promising for ECL evolution, especially for improving the throughput of the spectrum-resolved multiplexing ECL assay and biological imaging. Herein a biocompatible and environmentally friendly luminophore, that is, the methionine-stabilized Au nanoclusters (Met-Au NCs), are proposed to achieve efficient aqueous ECL of ∼835 nm with triethanolamine as coreactant. The Met-Au NCs not only demonstrate a 75 times enhanced ECL compared with the traditional Au NCs with bovine serum albumin as a capping agent but also can be employed as ECL tags to label proteins with a methionine linker and enable a highly sensitive NIR ECL bioassay. A sandwich-type NIR ECL immunosensor is constructed with the Met-Au NCs as tags and α-fetoprotein (AFP) as a model analyte and exhibits a wide linearity range from 3 fg·mL–1 to 0.1 ng·mL–1 with a limit of detection of 1 fg mL–1 (S/N = 3) as well as desired selectivity.