Detection of Thiols by o‐Quinone Nanocomposite Modified Electrodes

Abstract

A chemically modified glassy carbon (GC) electrode was developed as an amperometric sensor for detection of biological thiols. The electrode was modified by inclusion of co‐enzyme pyrroloquinoline quinone (PQQ) and a co‐catalyst of oxidized single wall carbon nanotubes (Ox‐SWNT) into a gold polypyrrole (Au‐PPy) nanocomposite matrix. The electrode (PQQ/Ox‐SWNT/Au‐PPy/GC) was characterized using scanning electron microscopy and cyclic voltammetry. Optimal conditions for the PQQ/Ox‐SWNT/Au‐PPy/GC electrode were determined and then utilized for the amperometric detection of L‐cysteine, N‐acetyl‐L‐cysteine, L‐penicillamine and D, L‐glutathione. The electrochemical response for each thiol in pH 3.2 citrate phosphate buffer at +450 mV (vs. Ag/AgCl) was found to be linear with limit of detections (LOD, S/N=3) ranging from 0.50 µM for L‐penicillamine to 1.55 µM for D, L‐glutathione with sensitivities of 30.2 nA/µM and 3.6 nA/µM respectively. The electrode design is simple and easy to construct using a minimum amount of co‐enzyme and co‐catalyst, resulting in detection methods with very good stability and improved sensitivity for thiol detection.

Electropolymerized Pyrrole-Based Conductive Polymeric Ionic Liquids and Their Application for Solid-Phase Microextraction

“…The process can produce uniform conducting organic thin films that strongly adhere to the support material with superior electrical contact. Organic heterocyclic monomers such as pyrrole, thiophene, aniline, and furan have all been explored and found to produce useful conductive coatings. − To date, these coatings have been widely studied for many applications involving fuel cells, analytical sensing devices, and extraction matrices. − Particularly relevant to this work, Pawliszyn and co-workers electropolymerized pyrrole to create a polymeric sorbent coating for solid-phase microextraction (SPME) of a variety of compounds, including ionic analytes and volatile organic compounds. − …”

Determination ofl-DOPA at an optimized poly(caffeic acid) modified glassy carbon electrode

“…46-54 CFA serves as an efficient electron shuttle between the analyte and electrode similar to other quinone/hydroquinone electrocatalysts utilized in our laboratory for amperometric sensing of various thiols and histamine. [55][56][57][58]…”

Inorganic–Organic Hybrid 3D Redox Nanoarchitecture for the Electrocatalytic Sensing of Thiols

“…They serve as antioxidant, inhibit cellular apoptosis, are involved in the formation of three-dimensional complex protein structure and control the cellular redox states. − Monitoring the concentration of these biological thiols is of great importance as their abnormal levels are related to cancer, aging, neurodegenerative, cardiovascular diseases, etc. − Although several analytical methods have been developed in the past, the electrochemical methods received considerable interest. The electrochemical oxidation of these thiols on unmodified electrode requires large overpotential and several attempts have been made to decrease the overpotential. − Achieving high sensitivity and a low detection limit is a challenging task in the development of electrochemical sensor for biological thiols. The electrochemical sensing of biological thiols can be achieved with catechol-like redox molecules in two different reaction pathways: − (i) Michael addition reaction of electrogenerated quinone with thiol and (ii) mediated-electrocatalytic oxidation of thiol by electrogenerated quinone to produce the corresponding disulfide.…”