A sensing platform for on-site detection of glutathione S-transferase using oxidized Pi@Ce-doped Zr-based metal-organic frameworks(MOFs)

The development of point-of-care testing (POCT) for glutathione S-transferase (GST) is an effective way to establish the mechanism of targeted monitoring of cancer chemotherapy drug metabolism. Assays for GST with high sensitivity as well as on-site screening have been urgently required to monitor this process. Herein, we synthesized oxidized Pi@Ce-doped Zr-based metal–organic frameworks (MOFs) by electrostatic self-assembly between phosphate and oxidized Ce-doped Zr-based MOFs. It was found that the oxidase-like activity of oxidized Pi@Ce-doped Zr-based MOFs was substantially increased after phosphate ion (Pi) assembly. And a stimulus-responsive hydrogel-based kit was constructed by embedding oxidized Pi@Ce-doped Zr-based MOFs into a PVA (polyvinyl alcohol) hydrogel system, we integrated a portable hydrogel kit with a smartphone for real-time monitoring of GST for quantitative and accurate analysis. The color reaction was triggered based on oxidized Pi@Ce-doped Zr-based MOFs with 3,3′,5,5′-tetramethylbenzidine (TMB). However, in the presence of glutathione (GSH), the above color reaction was hindered due to the reducibility of GSH. Catalyzed by GST, GSH can react with 1-chloro-2,4-dinitrobenzo (CDNB) to form an adduct, which caused the color reaction to occur again, resulting in the color response of the kit. In combination with ImageJ software, the kit image information acquired by smartphone could be converted into hue intensity, providing a direct quantitative tool for the detection of GST with a detection limit of 0.19mU·L−1. Based on the advantages of simple operation and cost-effectiveness, the introduction of the POCT miniaturized biosensor platform will meet the requirements of on-site quantitative analysis of GST.