Enzyme-Free Identification of Monosaccharide Enantiomers on TiO₂ Nanotube Array-Based Fabry–Pérot Interferometer

Chirality is a vital property across various domains, especially for biological activity. Herein, an enzyme-free sensing platform for monosaccharide enantiomer identification was developed by utilizing the Fabry-Pérot interferometer feature of TiO₂ nanotube arrays modified with enantioselective metal-organic framework and glucose oxidase-mimicking Au NPs. In this design, optical property is monitored by reflective interferometric Fourier transform spectroscopy (RIFTS), a highly sensitive technique for detecting changes in the average refractive index within nanotubular structures. Using glucose (Glu) enantiomers as the model targets, after the recognition of L-/d-Glu on mesoporous homochiral MIL-101 (Fe), Au NPs anchored in MIL-101(Fe) catalyze the oxidation of Glu molecules to produce hydrogen peroxide (H₂O₂). Benefiting from the confinement effect of frameworks, MIL-101(Fe), as an artificial enzyme with excellent peroxidase-like activity, catalyzes the conversion of 4-chloro-1-naphthol (4-CN) into insoluble precipitates. These gathered precipitates effectively change the average refractive index of the interferometric substrate. Based on the variation of effective optical thickness (Δ<i>E</i>OT) values, the enantioselective determination of l-Glu and d-Glu can be achieved. Moreover, the proposed RIFTS sensor also presents broad applicability for the identification of other monosaccharide enantiomers. As the enzyme-free homochiral interferometer is directly constructed on a Ti-metal sheet, the RIFTS platform offers a robust, sensitive, and low-cost device for monosaccharide enantiomer recognition.