Ascorbic acid-triggered electrochemical–chemical–chemical redox cycling for design of enzyme-amplified electrochemical biosensors on self-assembled monolayer-covered gold electrodes

• Published in: Journal of electroanalytical chemistry (Lausanne, Switzerland) Switzerland), 2014-10, Vol.731, p.78-83
• Main Authors: Xia, Ning, Liu, Lin, Wu, Ruijuan, Liu, Huiping, Li, Su-Juan, Hao, Yuanqiang
• Format: Article
• Language: English
• Subjects: Alkaline phosphatase; Ascorbic acid; Electrochemical biosensors; Ferrocenecarboxylic acid; Redox cycling; Self-assembled monolayer
• ISSN: 1572-6657; 1873-2569
• DOI: 10.1016/j.jelechem.2014.08.021

[Display omitted] •We reported ascorbic acid-triggered electrochemical–chemical–chemical redox cycling.•Ferrocenecarboxylic acid was used as the redox mediator.•Electrochemical sensor on SAM-covered electrodes can be developed with the recycling.•l-Ascorbic acid 2-phosphate was used as the enzyme substrate in the sensing system.•The performances were demonstrated in the competitive assays of β-amyloid peptides. l-Ascorbic acid 2-phosphate (AAP) is an optimal substrate for alkaline phosphatase (ALP) in electrochemical bioassays because of its low cost, good water solubility, less electrode passivation and high signal-to-background ratio. However, developing of electrochemical sensors with AAP as the enzyme substrate on self-assembled monolayer (SAM)-covered electrode is limited because the insulating SAM hinders the electron transfer between the electrode and ascorbic acid (AA, the enzymatic product of AAP). In this work, we first reported a strategy for developing AAP-based electrochemical biosensors on SAM-covered gold electrode. The method is based on AA-triggered “outer-sphere to inner-sphere” electrochemical–chemical–chemical (ECC) redox cycling with ferrocenecarboxylic acid (FcA) as the redox mediator. Specifically, AA produced from AAP facilitated the regeneration of FcA from its electrochemical-oxidation product (referred to as FcA+ in the text), leading to an increase in the anodic current of FcA. Electrochemically inert tris(2-carboxyethyl)phosphine (TCEP) was used as a chemical reducing reagent to regenerate AA from its oxidation product, thus amplifying the electrochemical signal. The applications and performances of the proposed method were demonstrated in the competitive assays of β-amyloid (Aβ) peptides. The theoretical simplicity and high sensitivity indicated that our work would be valuable for developing simple and sensitive electrochemical biosensors.