Characterization of the GM1 pentasaccharide–Vibrio choleratoxin interaction using a carbohydrate-based electrochemical system

Abstract

Antibody- or DNA-based electrochemical systems have been developed widely for several decades, while carbohydrate-based electrochemical systems have been rarely reported. Herein, we used an electrochemical detection system to understand the molecular relationships in carbohydrate–protein interactions that can provide useful information about biological processes in living organisms. This system was also helpful for the development of potent biomedical agents. Electrochemical detection was achieved through the observation of electrochemical response changes of ferrocyanide solution that resulted from the interaction of carbohydrate and protein using a modified GM1 pentasaccharide containing an anchoring thiol group that was directly immobilized on a gold electrode. As the concentration of the GM1 pentasaccharide increased, the current decreased gradually and saturated after 2 nM. We also found that the drop in current depended on the size of the carbohydrate (larger size of the carbohydrate denoted a higher slope of the current reduction), indicating that the current could be modulated by the molecular size of the carbohydrate as well as its concentration. This system was able to detect very low concentrations of carbohydrate (down to 20 fM), which highlighted the advantage of the electrochemical system. Interestingly, we found that a potential shift at the maximum current occurred upon interaction with cholera toxin proteins. By comparing results for different sizes of GM1 analogues, we surmise that the potential shift is closely associated with the specificity for the carbohydrate–protein interaction. Collectively, a carbohydrate-based electrochemical system can be leveraged for the facile and rapid analysis of carbohydrate–protein interactions.