TiO₂-In-MIL-101(Cr) with Visible Light-Induced Peroxidase Activity for Colorimetric Detection of Blood Glucose

In this work, metal-organic framework MIL-101(Cr) with regular morphology, stable structure, and good dispersion was prepared by the hydrothermal method. MIL-101(Cr) has two different sizes of pores, but after TiO₂ nanoparticles (NPs) were in situ prepared, the two pores disappear. The result demonstrates that TiO₂ NPs were located in the pores of MIL-101(Cr). TiO₂-decorated MIL-101(Cr) forms an inside type II heterojunction and the band gap energy is narrowed, which can promote electron-hole separation and enhance the light absorption. Therefore, the heterojunction shows a high visible light-induced peroxidase-like activity. Kinetic studies exhibit that the K _m value of TiO₂-in-MIL-101(Cr) to TMB is 0.17 mM, and the affinity of TiO₂-in-MIL-101(Cr) is higher than that of natural horseradish peroxidase (HRP). Then, a "turn-on" colorimetric assay based on TiO₂-in-MIL-101(Cr) was constructed for the detection of blood glucose. The detection range is 1-100 μM (R ² = 0.9950) with a limit of detection (LOD) of 1.17 μM. Compared with the clinical method, the constructed colorimetric method has accurate and reliable results for the clinical detection. The anti-interference experiment confirms that the method has high selectivity to glucose.