Alzheimer Disease Biomarker Detection Through Electrocatalytic Water Oxidation Induced by Iridium Oxide Nanoparticles

Abstract

Iridium oxide nanoparticles (IrO2 NPs) synthesized following a previously reported chemical route are presented as novel tags for immunosensing taking advantage of their electrocatalytic activity towards water oxidation reaction (WOR). Cyclic voltammetry and chronoamperometry for the evaluation of the IrO2 NPs electrocatalytic activity towards WOR at neutral pH were used. The chronoamperometric current recorded at a fixed potential of +1.3 V constituted the analytical signal allowing the quantification of IrO2 NPs at nM levels. Modification of the surface of citrate‐capped IrO2 NPs with anti‐Apolipoprotein E antibodies (αApoE) was successfully achieved and the as‐prepared conjugates were used for the electrocatalytic detection of ApoE Alzheimer disease (AD) biomarker in a magnetosandwich immunoassay, reaching a detection limit of 68 ng/mL. Human plasma of a patient suffering AD was also evaluated, estimating an ApoE concentration of 20 µg/mL which is in concordance with the obtained in previously reported approaches. This novel IrO2 NPs based electrocatalytic assay presents the advantage of the signal generation in the same medium where the immunoassay takes place (PBS, pH 7.4) avoiding the use of additional reagents which also opens the way to future integrated biosensing systems and platforms with interest for other proteins as well as DNA and cells analysis.

An iridium oxide nanoparticle and polythionine thin film based platform for sensitive Leishmania DNA detection

“…1B and Fig. 19,[22][23][24] After the oligonucleotide capture probe was attached to the IrO 2 NPs a charge transfer increase is observed (Fig. This demonstrates that the polythionine layer is well deposited and it enhances the electron transfer.…”

“…S3B, ESI †). 19,24,25 The morphological modification of SPE were also studied using scanning electron microscopy (SEM). Furthermore, the O 1s region shows two features.…”

“…8 With this aim, polythinoine layers have been reported to be used for proper modifications of sensors. 19,20 The platform developed shows good performance for electrochemical sensing of PCR amplified DNA of dog affected by Leishmania, this target is used as a proof a concept. [11][12][13][14] However, various issues like poor compatibility of immobilizing materials on the transducer, poor binding of DNA, creation of inactive or poor conducting layers and less surface area including poor stability were raised.…”

Nanomaterials towards Biosensing of Alzheimer’s Disease Biomarkers

“…AgNPs [88], magnetic nanoparticles [82,89,90] and QDs [48,90] have also been used in the development of biosensors for AD diagnosis but to a lesser extent ( Table 2).…”

“…Taking advantage of the excellent structure of PMMs for antibody immobilization, the developed immunosensor was successfully applied in real clinical CSF, serum and plasma samples of patients suffering from AD. Rivas et al [89] explored the excellent electrocatalytic activity of iridium oxide nanoparticles towards the water oxidation reaction and employed this as a new signaling mechanism in protein diagnosis (Figure 10). The procedure is similar to that previously described by de la Escosura-Muñiz [82] but, instead of AuNPs, the team used iridium oxide nanoparticles.…”