Abstract:

Glutathione(GSH) and cysteine(Cys) are biological thiols that play vital roles in maintaining cellular functions. GSH is a thiol-group-containing tripep-tide, which has a pivotal role in maintaining the redu-cing environment in cells. Cys is a biomarker for various medical conditions, and a disease-associated physiological regulator. In this work, a high sensitive electrochemical biosensor for GSH and Cys detection was constructed using Au nanoparticles enhanced signal amplification. DNA1 and DNA2 were all poly-T DNA probes. Firstly, DNA1 was modified on the surface of electrode, and then DNA2 was modified on the AuNPs. In the presence of Hg²⁺, the binding of Hg²⁺ with thymine(T) was employed to form T-Hg²⁺-T structure and thus DNA2 modified AuNPs could be captured on the electrode surface. The added GSH(or Cys) could selectively coordinate with Hg²⁺ of the T-Hg²⁺-T structure, which resulted in the departure of AuNPs from the electrode surface. Since DNA modified on AuNPs could bind a large number of electric active RuHex via electrostatic interaction, the chronocoulometry signal was reduced obviously, and then GSH(or Cys) could be detected according to the change of chronocoulometry signal. The results showed that the electrochemical biosensor was highly sensitive, and it could detect as low as 10 pmol/L for GSH(or Cys). It was about 2-3 orders of magnitude lower than those of fluorescent and colorimetric methods. Moreover, eight kinds of amino acids were used as control to investigate the selectivity of this electrochemical biosensor, and the results showed that this electrochemical biosensor showed good selectivity.

Key words: Electrochemical biosensor, Au nanoparticles, DNA, Glutathione, Cysteine