High selective and sensitive capillary electrophoresis-based electrochemical immunoassay enhanced by gold nanoparticles.

A novel capillary electrophoresis (CE)-based electrochemical (EC) immunoassay (IA) enhanced by gold nanoparticles (AuNPs) was developed for the determination of shellfish toxins. After competitive immunoreaction between shellfish toxin antigen (Ag), horseradish peroxidase (HRP)-labeled antigen (Ag*), and limited antibody (Ab), the immune sample was introduced into capillary and conjugated with AuNPs. The presence of AuNPs modifies the mobilities of analytes and improves separation resolution between analytes. Furthermore, the AuNPs were used as multianalyte carriers of the excess signaling Ag* and the bound enzyme-labeled complex (Ag*-Ab) to achieve an amplification of EC signal. Enhanced resolution and sensitivity were obtained by using bioconjugates featuring HRP labels linked to AuNPs. The four shellfish toxins were baseline separated by using AuNPs. The relative standard deviation (RSD) values of the migration time were 1.3-3.5% for intraday and 3.1-4.6% for interday, respectively. The RSDs of the peak area were 2.8-4.6% for intraday and 4.1-6.9% for interday, respectively. The limits of detection (S/N=3) were in the range of 3.1-36.7 ng/L. The enhanced CE based EC-IA with AuNPs labels was successfully applied for the simultaneous determination of four shellfish toxins in shellfish samples. With high resolving power and sensitivity, the proposed method has shown great potential to become an attractively alternative method for simultaneous determination of diverse red tide poisons in shellfish samples.