Combining a gold nanoparticle-polyethylene glycol nanocomposite and carbon nanofiber electrodes to develop a highly sensitive salivary secretory immunoglobulin A immunosensor

This study describes the development of a highly sensitive electrochemical immunosensor for the detection of salivary secretory Immunoglobulin A (sIgA). Immunosensor fabrication involves a gold nanoparticle (AuNP) and polyethylene glycol (PEG) nanocomposite deposited on modified carbon nanofiber electrodes (CNF-SPE). Anti-sIgA monoclonal antibody (mAbS) is immobilized onto the nanocomposite, followed by blocking with BSA. This fabrication technique allows both label-free and enzyme-free detection of sIgA. Immunosensor response was measured by square wave voltammetry, while cyclic voltammetry was used for characterization. For further characterization FE-SEM was used to analyze layer-by-layer fabrication. Despite the simple fabrication technique employed, a large increase in sensitivity (3000-fold) was achieved, with an experimentally determined detection limit of 500 fg mL(-1). As well as, this immunosensor demonstrated excellent stability over time, reproducibility, selectivity, and resistance to common interferences. The latter two are of great importance when performing real sample analysis on biological fluids such as saliva. Indeed, detection of sIgA in saliva samples yielded excellent recovery percentages; 110%, 98% and 86% for 250, 500 and 1000 pg mL(-1) respectively, thus demonstrating the potential to analyze real saliva samples and highlighting this as a highly sensitive platform to monitor sIgA. (C) 2017 Elsevier B.V. All rights reserved.