Simultaneous Electrochemical Determination of Glutathione and Glutathione Disulfide at a Nanoscale Copper Hydroxide Composite Carbon Ionic Liquid Electrode

In vivo detection of glutathione disulfide and oxidative stress monitoring using a biosensor

A highly sensitive in vivo biosensor for glutathione disulfide (GSSG) is developed using covalently immobilized-glutathione reductase (GR) and -β-nicotinamide adenine dinucleotide phosphate (NADPH) on gold nanoparticles deposited on poly[2,2':5',2″-terthiophene-3'-(p-benzoic acid)] (polyTTBA). The fabricated biosensor was characterized with SEM, TEM, XPS, and QCM. Analytical parameters affecting the biosensor performance were optimized in terms of applied potential, NADPH:GR ratio, temperature, and pH. A linear calibration plot is obtained using chronoamperometry in the dynamic range between 0.1 μM and 2.5 mM of GSSG, with a detection limit of 12.5 ± 0.5 nM. The developed biosensor is applied to detect GSSG in a real plasma sample. A microbiosensor was applied to detect the in vivo GSSG concentration to monitor the oxidative stress caused by diquat and t-butyl hydroperoxide. The results obtained are reliable, implying a promising approach for a GSSG biosensor in clinical diagnostics and oxidative stress monitoring.

Low-potential photoelectrochemical biosensing using porphyrin-functionalized TiO₂ nanoparticles

A novel photoelectrochemical biosensing platform for the detection of biomolecules at relatively low applied potentials was constructed using porphyrin-functionalized TiO₂ nanoparticles. The functional TiO₂ nanoparticles were prepared by dentate binding of TiO₂ with sulfonic groups of water-soluble [meso-tetrakis(4-sulfonatophenyl)porphyrin] iron(III) monochloride (FeTPPS) and characterized by transmission electron microscopy; contact angle measurement; and Raman, X-ray photoelectron, and ultraviolet-visible absorption spectroscopies. The functional nanoparticles showed good dispersion in water and on indium tin oxide (ITO) surface. The resulting FeTPPS-TiO₂-modified ITO electrode showed a photocurrent response at +0.2 V to a light excitation at 380 nm, which could be further sensitized through an oxidation process of biomolecules by the hole-injected FeTPPS. Using glutathione as a model, a methodology for sensitive photoelectrochemical biosensing at low potential was thus developed. Under optimal conditions, the proposed photoelectrochemical method could detect glutathione ranging from 0.05 to 2.4 mmol L⁻¹ with a detection limit of 0.03 mmol L⁻¹ at a signal-to-noise ratio of 3. The photoelectrochemical biosensor had an excellent specificity against anticancer drugs and could be successfully applied to the detection of reduced glutathione in gluthion injection, showing a promising application in photoelectrochemical biosensing.