Selective SERS identification and quantification of glucose enantiomers on homochiral MOFs based enzyme-free nanoreactors

Abstract

Enantiomeric identification plays a critical role in diverse fields ranging from pharmaceutics, biologics, and stereoselective synthesis to daily life. In this study, an enantioselective surface-enhanced Raman scattering (SERS) substrate was developed by integrating homochiral MIL-101(Fe) with oxidase (GOx)-mimicking Au nanoparticles (Au/Chiral-MIL-101(Fe)) for identification and quantification of chiral molecules. Using L/d-glucose (Glu) as the model enantiomers, the homochiral environment of Au/Chiral-MIL-101(Fe) exhibited selective recognition abilities for Glu enantiomers. The captured Glu was further oxidized to hydrogen peroxide (H2O2) by GOx-like activity of Au nanoparticles. The generated H2O2 molecules reduced Fe(III) nodes in MIL-101(Fe) to Fe(II) for the growth of Prussian blue (PB) on site. Benefitting from the pre-concentrated feature and confinement effect of the porous metal–organic frameworks (MOFs) structure, the Au/Chiral-MIL-101(Fe) hybrid based nanoreactors exhibited high catalytic performance for H2O2 generation and further PB growth, resulting in an excellent sensitivity for Glu quantification. The enantioselective discrimination between l-Glu and d-Glu was directly determined from the intensity of PB signals at 2150 cm−1. Using this sensing strategy, Glu enantiomers could be quantified with a limit of detection (LOD) of 0.09 µM for l-Glu and 0.08 μM for d-Glu. Owing to its enzyme-free nature and universal characteristic for the discrimination of other monosaccharide enantiomers, this design provides an attractive substrate for sensing chiral molecules by Raman technology.