Ultrasensitive and facile electrochemical detection of hydrogen sulfide in rat brain microdialysate based on competitive binding reaction

• Published in: Analytical and bioanalytical chemistry 2017-02, Vol.409 (4), p.1101-1107
• Main Authors: Li, Bo, Li, Lin, Wang, Keqing, Wang, Chao, Zhang, Linlin, Liu, Kun, Lin, Yuqing
• Format: Article
• Language: English
• Subjects: Alzheimer's disease; Analytical Chemistry; Biochemistry; Brain; Characterization and Evaluation of Materials; Chemical properties; Chemical reactions; Chemistry; Chemistry and Materials Science; Copper; Cysteine; Electrochemical analysis; Electrochemistry; Electrodes; Electrons; Food Science; Gold; Homocysteine; Hydrogen; Hydrogen sulfide; Laboratory Medicine; Measurement; Methods; Monitoring/Environmental Analysis; Observations; Physiological aspects; Reagents; Research Paper; Sensors
• ISSN: 1618-2642; 1618-2650
• DOI: 10.1007/s00216-016-0030-y

In this study, a sensitive and facile method with wide linear range and low detection limit for detecting hydrogen sulfide in rat brain microdialysate was developed. The design of the sensor is based on the competitive binding reaction principle, in which cysteine was self-assembly immobilized on the surface of gold electrode, and then the Cu 2+ as the electrochemical probe was anchored to the cysteine film through coordination bonding with carboxyl (−COOH) and amino group (−NH 2 ) to form the Cu 2+ /Cys/Au electrode. The Cu 2+ /Cys/Au electrode can serve as an electrochemical H 2 S sensor through a ligand exchange reaction, which may come from the greater affinity of H 2 S than cysteine to the gold surface due to a steric hindrance reason. The hydrogen sulfide cuts off the S-Au bonds between cysteine and Au electrode and leads to the Cu 2+ drop off from electrode, resulting in a decrease in the redox signal of Cu 2+ , thereby creating a current that is indirectly proportional to the logarithm of the concentration of H 2 S dissolved at the sensor surface. The current response, i.e., signal output, is in wide linearity to logarithm of the concentration of H 2 S in the range of 0.01–100.0 μM with ΔI/μA = 0.0857 lgCH 2 S(nM) +0.124 and very low detection limit 5 nM (S/N = 3). The assay demonstrated here is highly selective with respect to alleviating the interference of other thiol-containing species such as glutathione (GSH), homocysteine (Hcy), and cysteine commonly existing in the brain. The basal level of H 2 S in the microdialysate from the hippocampus of rats is determined to be around 8.6 ± 3.2 μM. The method demonstrated here is facile but reliable and durable and is envisaged to be applicable to understanding the chemical essence involved in physiological and pathological events associated with H 2 S. Graphical abstract By rationally tailoring the gold electrode surface through the competitive binding interaction of gold electrode between cysteine and H 2 S, we have successfully designed a simple, highly sensitive, and selective method for electrochemical sensing of H 2 S in brain microdialysate.