Prussian blue modified metal-organic framework MIL-101(Fe) with intrinsic peroxidase-like catalytic activity as a colorimetric biosensing platform

In this paper, a nanosized porous PB/MIL-101(Fe), was facilely prepared with a uniform octahedral structure by growing Prussian blue (PB) on the microporous metal-organic framework MIL-101(Fe), and confirmed by cyclic voltammogram (CV), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. It was demonstrated to possess intrinsic peroxidase-like activity and could catalytically oxidize 3,3',5,5'-tetramethylbenzidine (TMB), o-phenylenediamine (OPD), and 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (AzBTS) by H2O2 in solution to produce a typical colour change. As a novel peroxidase mimic material, PB/MIL-101(Fe) shows high catalytic efficiency. Kinetic analysis of as the as-prepared PB/MIL-101(Fe) was studied, and it gave a linear absorbance response from 2.40 mu M to 100 mu M with a limit of detection (LOD) of 0.15 mu M. It indicated that the catalytic behavior was consistent with typical Michaelis-Menten kinetics and follows a ping-pong mechanism. Interestingly, the K-m values for PB/MIL-101( Fe) with respect to TMB and H2O2 is 0.127 and 0.0580 mM were lower than those of MIL-101(Fe) (0.490 and 0.620 mM for TMB and H2O2), respectively. This is probably attributed to more active sites and the pores of the PB/MIL-101(Fe) for peroxidase substrates. More importantly, it can be easily functionalized with different compounds including silica coating (TEOS), 3-aminopropyltriethoxysilane (APTES), polyethylene glycol (PEG) or folic acid (FA) to make it biocompatible. The results reveal that the stability, ease of production and versatility of PB/MIL-101(Fe) nanoparticles could result in them being used as a promising tool for cancer cell detection. With these findings, a simple and sensitive colorimetric biosensing platform has been established.