Cerium dioxide-based nanostructures as signal nanolabels for current detection in the immunosensing determination of salivary myeloperoxidase

Abstract

This work reports the first electrochemical immunoplatform involving the use of synthesized cerium dioxide nanoparticles (CeO2NPs) / multi-walled carbon nanotubes (MWCNTs) composites as signal nanolabels for the determination of salivary myeloperoxidase (MPO), one of the proteins suggested as diagnostic biomarkers of periodontitis. The immunosensing device profits the benefits of CeO2NPs in terms of fast electron transfer and the catalytic activity and prevents the CeO2NPs tendency to agglomerate by decoration over MWCNTs, also providing high sensitivity. After a thorough characterization of the CeO2NPs/MWCNTs using various techniques and optimization of the variables involved in the preparation of the immunoplatform, a sandwich-type immunoassay was implemented with specific MPO capture and biotinylated detection antibodies. The use of horseradish peroxidase-streptavidin (HRP-Strept) or CeO2NPs/MWCNTs-(HRP-Strept) as labels for the amperometric detection at screen printed carbon electrodes (SPCEs) at −0.20 V vs. Ag pseudo-reference electrode using the H2O2/hydroquinone (HQ) system, was compared. The method developed involving CeO2NPs/MWCNTs-(HRP-Strept) provided a linear calibration plot for MPO over the 1.0 to 100.0 ng mL−1 (R2 = 0.994) range with a limit of detection value of 0.40 ng mL−1. The immunoplatform was applied to the analysis of saliva from volunteers showing that the method allowed discrimination between healthy individuals and patients diagnosed with periodontitis through the determination of MPO in 1000-times diluted saliva. The obtained results agreed with those provided by an ELISA kit, this latter requiring a much longer assay time (4 h vs 2 h).