Pillar[6]arene: Electrochemistry and application in electrochemical (bio)sensors

Abstract

Electrochemical behavior of pillar[6]arene (P[6]A) was investigated for the first time in solution and on the surface of the glassy carbon electrode covered with carbon black by cyclic voltammetry and electrochemical quartz crystal microbalance. Reversible redox peaks on voltammograms corresponded to the redox conversion of hydroquinone units of the macrocycle with no effect of intramolecular hydrogen bonds. The adsorption of the macrocycle oxidation products did not affect reversibility of the electron transfer. The P[6]A adsorption on the carbon black improved the stability of redox characteristics against those in homogeneous conditions, especially in basic media. The adsorbed P[6]A retained its ability to supramolecular interactions and showed mediator properties attractive for application in electrochemical (bio)sensors. This was proved by determination of paraquat after its accumulation on the pillar[6]arene – carbon black coating with the limit of detection of 0.5 μM. The P[6]A modified electrode was also applied as a transducer of the acetylcholinesterase biosensor. Mediated oxidation of thiocholine was amperometrically monitored at 0.25 V. The biosensor made it possible to determine berberine, a reversible inhibitor of the enzyme, and two anticholinesterase pesticides, carbofuran and malaoxon. The biosensor showed high stability of the response and low detection limits of the inhibitors (1 nM for berberine and 0.1 nM for carbofuran and malaoxon). The acetylcholinesterase biosensors were also tested on spiked samples of urine (berberine) and peanut. The recovery calculated from the calibration curve of standard analyte solutions was in the range from 86 to 113%.