Electrochemical assay of anti-tetanus toxoid monoclonal antibody by silver enhancement of gold nanoparticles at carbon nanotubes modified glassy carbon electrode

Tetanus is caused by the toxin secreted by Clostridium tetani. Due to the rapid infection with this bacterium, it is so important to investigate the tetanus immunity of people. Therefore, electrochemical biosensors, as one of the most effective tools in this regard, have demanded characteristics such as being fast, simple, cost-effective and portable. However, their detection sensitivity is not sufficient. Hereon, silver enhancement of gold-nanoparticles was proposed for the improvement of detection. Hence, the current study applied gold-nanoparticles as label, following with silver enhancement, to investigate the yes/no electrochemical detection of anti-tetanus toxoid antibodies in the indirect immunoassay utilizing glassy-carbon electrodes modified by carbon nanotubes. The analytical procedure consists of the reactions of the tetanus toxoid with the antibody at electrode, so that followed by the interaction of gold-labeled secondary antibody and then silver enhancement process. In this study, the cyclic-voltammeter variation and difference of gold to silver signal based on silver ions fluctuations were also investigated. The results indicated that ∆Ep increased from 0.24 V before silver enhancement reaction to 0.57 V after the silver enhancement. The results also demonstrated that after silver enhancement, current significantly increased and current plot at Ecp transferred to positive potentials and at Eap moved to negative potentials. In conclusion, this method increases the detection sensitivity and can simply use to other bio-molecules detection.