Label-free impedimetric glycosensor based on β-galactose-functionalized gold electrode for the determination of cholera toxin

Abstract

A label-free impedimetric glycosensor has been developed for the direct detection of cholera toxin (CT). The glycosensor has been fabricated by forming the self-assembled monolayers of β-galactose derivatives containing poly-ethyleneglycol (PEG) spacer on gold electrode surfaces. The selective binding of CT to the β-galactose receptors on the fabricated glycosensor has been directly monitored by electrochemical impedance spectroscopy in the presence of 5.0mM K3Fe(CN)6/K4Fe(CN)6 (1:1, v/v) redox couple. gmonolayers on gold electrode surface has been determined to be ca. 2.53×1010M−1, indicating that the present glycosensor can selectively capture the target CT from sample solutions. Therefore, the present monosaccharide β-galactose derivative can be used as a receptor for CT as an alternative to CT-specific antibodies or pentasaccharide ganglioside GM1, most widely used in conventional CT assays. The present glycosensor can detect CT in the concentration range from 1.18×10−12M to 1.18×10−9M (r2=0.963) with a limit of detection (S/N=3) down to 7.83×10−13M, which is much lower than those obtained with other detection methods. Since the present glycosensor-based CT assay does not require complex and time-consuming signal amplification steps generally employed in sandwich-type immunoassays, it enables the simple and rapid detection of CT.