Electrochemical biosensor using SnO2 colloidal quantum wire for monitoring the interaction of microcystin antigen–antibody

Electrochemical sensors that incorporate immunoassay principles have the ability to monitor dynamic processes of antigen–antibody interactions in real time. In this study, a gold electrode was modified with tin dioxide colloidal quantum wire (SnO 2 QWs) and then coated with the leucine/arginine subtype microcystin (MC-LR) antibody. The active site of SnO 2 QWs that was not bound by MC-LR antibody was then passivated with bovine serum protein (BSA). When the MC-LR antigen binds specifically to the antibodies on the electrode's surface, it triggers electrochemical reactions and generates electrical signals at specific voltage conditions. The SnO 2 QW exhibits excellent electron transport ability, and its ability to form a loose and porous microstructure on the gold electrode surface, which is conducive to the receptor function of the biosensor. The results show a high affinity between the MC-LR antigen and antibody, ranging from 1 pg/mL to 10 ng/mL of MC-LR antigen concentration. The kinetic characteristics of the immune reaction between MC-LR antigen and antibody were elucidated, obtaining a binding constant of 1.399 × 10 11 M −1 and a dissociation constant of 7.147 pM, demonstrating the potential of electrochemical biosensing technology in biomolecular interactions.