Metal organic framework MIL-53(Fe) as an efficient artificial oxidase for colorimetric detection of cellular biothiols.

Biothiols play critical roles in many biological processes and their aberrant is related to a variety of syndromes. A simple and reliable colorimetric method is developed in this work for biothiols detection based on an oxidase mimic, a metal organic framework (MOF) MIL-53(Fe), and a peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB). In this design, MIL-53(Fe) is utilized to catalyze the conversion of TMB to a blue colored 3,3',5,5'-tetramethylbenzidine diimine, which can be read on a spectrophotometer at 652 nm. The oxidation-induced blue color generation can be efficiently inhibited by biothiols, thus a colorimetric analytical method is proposed for biothiols detection based on the above system. Under optimal conditions, a linear relationship in a range from 1 to 100 µM and a limit of detection (LOD) at 120 nM are achieved with Cys as a model target. The developed platform is further applied to evaluate cellular biothiols in normal (RWPE-1) and cancer (LNCap) cell lines, revealing that the overall biothiols level in LNCap is much higher than that in RWPE-1. This work renders a powerful tool for identifying cancer cells in a simple manner for biomedical diagnosis associated with biothiols.

FePO4 embedded in nanofibers consisting of amorphous carbon and reduced graphene oxide as an enzyme mimetic for monitoring superoxide anions released by living cells.

FePO4 is biocompatible and can act as a kind of promising enzyme mimetic. Unfortunately, the electrical conductivity of FePO4 is poor. In order to enhance its conductivity, FePO4 was embedded into nanofibers consisting of amorphous carbon and reduced graphene oxide (rGO) by an electrospinning technique. As a sensing material for monitoring superoxide anion (O2•-) and typically operated at 0.5 V (vs. SCE), it displays high sensitivity (9.6 µA⋅µM-1⋅cm-2), a low detection limit (9.7 nM at S/N = 3), a wide linear response range (10 nM to 10 µM), and fast response (1.6 s). Due to its low detection limit and fast response, the sensor in our perception has a large potential for detecting superoxide anions released by HeLa cancer cells. Graphical abstract Schematic of the microstructure of FePO4/C and FePO4/rGO-C nanofibers, a photograph of cancer cells (HeLa), and the electrochemical response towards O2-• of the sensor.