Construction of Peroxidase-like Metal–Organic Frameworks in TiO2 Nanochannels: Robust Free-Standing Membranes for Diverse Target Sensing

• Published in: Analytical chemistry (Washington) 2021-07, Vol.93 (27), p.9486-9494
• Main Authors: Xu, Huijie, Guo, Junli, Yang, Lingling, Gao, Zhida, Song, Yan-Yan
• Format: Article
• Language: English
• Subjects: Acetylcholinesterase; Chemistry; Denaturation; Electrochemistry; Environmental conditions; Food safety; Inspection; Iron; Membranes; Metal-organic frameworks; Nanochannels; Oxidation; Peroxidase; Robustness; Sensors; Substrates; Thiols; Titanium; Titanium dioxide; Toxicity
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/acs.analchem.1c01287

The high cost and easy denaturation of natural enzymes under environmental conditions hinder their practical usefulness in sensing devices. In this study, peroxidase (POD)-like metal–organic frameworks (MOFs) were in situ grown in the nanochannels of an anodized TiO2 membrane (TiO2NM) as an electrochemical platform for multitarget sensing. By directly using a nanochannel wall as the precursor of metal nodes, Ti-MOFs were in situ derived on the nanochannel wall. Benefitting from the presence of bipyridine groups on the ligands, the MOFs in the nanochannels provide plenty of sites for Fe3+ anchoring, thus endowing the resulting membrane (named as Fe3+:MOFs/TiO2NM) with remarkable POD-like activity. Such Fe3+-induced POD-like activity is very sensitive to thiol-containing molecules owing to the strong coordination effect of thiols on Fe3+. Most importantly, the POD-like activity of nanochannels can be in situ characterized by the current–potential (I–V) properties via catalyzing the oxidation of 2,2′-azinobis­(3-ethylbenzothiazoline-6-sulfonate) (ABTS) substrate to the corresponding positively charged product ABTS•+. As a proof-of-concept application, the free-standing POD-like membranes were applied as a label-free assay in sensing cysteine, as well as monitoring acetylcholinesterase (AChE) activity through the generated thiol-containing product. Furthermore, based on the toxicity effect of organophosphorus (OP) compounds on AChE, the robust membranes were successfully utilized to evaluate the toxicity of diverse OP compounds. The POD-like nanochannels open up an innovative way to expand the application of nanochannel-based electrochemical sensing platforms in drug inspection, food safety, and environmental pollution.