Enzymatic Preparation of Plasmonic-Fluorescent Quantum Dot-Gold Hybrid Nanoprobes for Sensitive Detection of Glucose and Alkaline Phosphatase and Dual-Modality Cell Imaging.

Herein, we develop a route to prepare bifunctional plasmonic-fluorescent quantum dot-gold (QD-Au) hybrid nanoprobes by use of enzymatic reactions. Two bioenzymes, glucose oxidase (GOx) and alkaline phosphatase (ALP) were chosen for the enzymatic preparation of core-satellite or core-shell type CdSe/ZnS@Au hybrid nanostructures. The enzymatic products, H2O2 and l-ascorbic acid, of the two enzymes were exploited as mild reducing agents for controlled Au deposition on QD surfaces. The polymer multilayers by layer-by-layer assembly were used to adjust the separation between QD core and plasmonic Au, which can effectively reduce the quenching effect of the Au on QDs. The as-prepared QD@Au hybrid nanostructures are excellent dual-modality imaging nanoprobes, and can be used for fluorescence and dark-field scattering dual-imaging of MCF-7 cells. More importantly, the two enzymatic reaction systems can be explored for sensitive and selective detection of glucose and alkaline phosphatase, respectively, by monitoring the fluorescence spectra change of QD@Au hybrid nanoparticles, which is very useful for the glucose- and ALP-related disease diagnosis.