Metal-organic framework MIL-53(Fe): facile microwave-assisted synthesis and use as a highly active peroxidase mimetic for glucose biosensing

The octahedral structure of MIL-53(Fe) was facilely prepared by a microwave (MW)-assisted approach, and confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The MIL-53(Fe) MOFs were further characterized by thermo gravimetric (TG) analysis and fourier transform infrared (FTIR) spectroscopy. It is found that the as-prepared MIL-53(Fe) exhibits intrinsic peroxidase-like activity, and could catalytically oxidize 3,3 ',5,5 '-tetramethylbenzidine (TMB), ABTS and OPD by H2O2 to produce a typical coloured reaction. The Michaelis-Menten behavior of the as-prepared MIL-53(Fe) was studied. The Km value of the as-prepared MIL-53(Fe) with H2O2 as the substrate was 0.03 mM, which was at least seven times lower than that of Fe-MIL-88NH(2) and hemin@MIL-53(Al)-NH2. Interesting, the Km values of the as-prepared MIL-53(Fe) with H2O2 and TMB as the substrates were both lower than those of the MIL-53(Fe) obtained by conventional electric (CE) heating-based solvothermal method. This is probably attributed to the purely octahedral structure and small sized crystals of the MIL-53(Fe) obtained by MW-based synthesis method, confirming that the MW-based synthesis method promised advantages of simplicity, fast crystallization and good phase selectivity. Results of electron spin resonance (ESR) experiments indicated that the as-prepared MIL-53(Fe) exhibited catalytic ability to decompose H2O2 into (OH)-O-center dot radicals. On this basis, a simple, sensitive and selective method for glucose detection was developed by coupling the oxidation of glucose catalyzed by glucose oxidase (GOx). As low as 0.25 mu M glucose could be detected with a linear range from 0.25-20 mu M. The proposed method was successfully used to determine glucose in real human serum samples.