A novel electrochemical sensor for detection of cysteine based on a Methacrylic Ester compound probe

1,4-bis(2-methacryloxy)benzene (BMOB) was synthesized through a facile one-step reaction and was used as an electrochemical probe for the selective determination of cysteine. BMOB reacted with the sulphydryl group of cysteine by a Michael addition reaction, then underwent the intramolecular cyclization reaction and released the electroactive phenolic substance. The accurate determination of cysteine was realized by detecting the oxidation electrical signal of the electroactive phenolic substance on the bare glassy carbon electrode. The reaction mechanism between BMOB and cysteine was proved by high-resolution mass spectrum and differential pulse voltammetry. The experimental conditions were optimized to obtain higher sensitivity. A plot of peak current versus cysteine concentration exhibited a well-linear relationship in the range of 5.0 μM - 100.0 μM, with a correlation coefficient of 0.9978. The limit of detection was calculated to be 0.29 μM (S/N = 3). BMOB was insensitive to 6-Mercapto-1-hexanol, homocysteine and glutathione, indicating relatively high selectivity. The developed electrochemical sensor based on BMOB-cysteine reaction successfully detected cysteine in spiked rat serum and Paediatric Compound Amino Acid Injection(18AA-I)with high selectivity, reproducibility and accuracy. Compared with other complicated analytical methods or tedious electrode modification processes, this work provided a simple and convenient approach for the accurate detection of cysteine on traditional unmodified electrodes.