A sensitive electrochemical sensor for glutathione based on specific recognition induced collapse of silver-contained metal organic frameworks.

An electrochemical sensor capable of detecting glutathione (GSH) with high sensitivity and selectivity was developed based on the unique novel electroactive silver-based metal organic framework (Ag-MOF). The Ag-MOF obtained by silver nitrate and 1,3,5-benzoic acid (H3BTC) was thoroughly characterized and was modified onto the electrode via facile drop-casting method. The electrochemical response of GSH on the Ag-MOF modified electrode showed a significant reduction in the current signal because the Ag-GSH complex had stronger specific affinity than Ag-H3BTC and resulted in the collapse of the Ag-MOF. This sensor demonstrated an extensive linear dynamic range of 0.1 nM-1 µM, along with the low detection limit of 0.018 nM. Additionally, it exhibited good reproducibility, stability, and resistance to interfering compounds. The Ag-MOF modified electrode demonstrated superior performance attributed to its rapid electron transfer rate, outstanding electrochemical redox activity, and specific recognition/competitive reaction. These factors improved both sensitivity and selectivity. The high anti-interference ability allowed for the selective detection of GSH in intricate surroundings. In the real sample testing, the RSD was lower than 3.1% and the recovery was between 98.1 and 103%. This research highlights the potential of Ag-MOFs in developing electrochemical sensors and their promising applications in determining GSH for food screening and early disease diagnosis.

Picomolar glutathione detection based on the dual-signal self-calibration electrochemical sensor of ferrocene-functionalized copper metal-organic framework via solid-state electrochemistry of cuprous chloride.

Chemical biosensing techniques are essential for food analysis and disease diagnosis. Nanomaterials with redox activity show great potential in electrochemical analysis, acting as signal labels or signal amplification unit, which can reflect the targets concentration in foods and biological samples. Here, an ultra-sensitive dual-signal intrinsic self-calibration electrochemical platform for GSH was firstly fabricated based on the novel electroactive nanomaterial of ferrocene-functionalized copper metal-organic framework (Fc-Cu-MOF). Due to the solid-state electrochemical property of cuprous chloride (CuCl), a sharp characteristic peak with an increased signal appears with the coexistence of chloride ions in solution. The stronger specific affinity between Cu+ and GSH than that of Cu+ and Cl- triggers a "crowding effect" that causes the current signal of CuCl decrease greatly. Meanwhile, the peak current of ferrocene keeps unchanged as an internal reference. Based on the ratio of the peak current variation (ΔICu/ΔIFc) as the signal output, Fc-Cu-MOF modified electrode showed wider linear range in 0.1 nM -1 µM for GSH with the detection limit as low as 0.025 nM. And the sensor was successfully applied in the determination of GSH with excellent recoveries in various real samples such as food and serum samples, providing good prospect in application of bioanalysis and food screening.

Signal On-Off Electrochemical Sensor for Glutathione Based on a AuCu-Decorated Zr-Containing Metal-Organic Framework via Solid-State Electrochemistry of Cuprous Chloride.

A novel signal on-off glutathione (GSH) electrochemical sensor was developed based on a AuCu bimetal-decorated Zr-containing metal-organic framework (Zr-MOF), in which a signal amplification strategy promoted by solid-state electrochemistry of cuprous chloride (CuCl) was used. The Zr-MOF with a large surface area can be effectively used as the substrate for the in situ growth of AuCu bimetals to obtain the Zr-MOF@AuCu nanocomposite. The interaction between Cu in Zr-MOF@AuCu and Cl- in the solution accompanied with the formation of CuCl displays an enlarged stable oxidation current, which greatly declines with the addition of GSH owing to the specific Cu-GSH interaction. The conversion of CuCl into Cu-GSH triggered the "crowding-out effect" and resulted in a sharp drop in the peak current of CuCl, which can realize the ultrasensitive and selective detection of GSH. The detection mechanism was investigated, and the detection range was 10 pM-1 mM with the detection limit as low as 2.67 pM. The special response mechanism for the detection of GSH allows the highly selective detection of GSH in various real samples with reliable results, endowing the proposed electroanalysis sensor with broad application prospects in biological and food analysis.