Reagentless Redox Capacitive Assaying of C-Reactive Protein at a Polyaniline Interface

Abstract

Methods that enable the sensitive and label-free detection of protein biomarkers are well-positioned to make potentially significant contributions to diagnostics and derived personalized healthcare. In support of this goal, a myriad of (electrochemical) methodologies have been developed; recently, electrochemical capacitance spectroscopy emerged as an impedance-derived approach which, in employing surface-confined redox-transducers, circumvents problems associated with the use of solution-phase redox-probes. Herein, we expand this scope by utilizing phytic acid-doped polyaniline as a novel redox-charging polymer support enabling the reagentless assaying of C-reactive protein in serum with good sensitivity. The construction of the sensory interface via electropolymerization allows facile tuning of the surface coverage and redox (capacitive) properties of the polymers, which, in turn, modulate both assay selectivity, fouling, and sensitivity. Significantly, this methodology is readily extendable to a wide range of electrode materials and analytes.

Introducing polymer conductance in diagnostically relevant transduction

“…A plot of interfacial relative response ( , generates a standard curve ( Fig. 2 d), with a resolved sensitivity of 30.9% per decade, higher than that typically reported for capacitance sensors ( Baradoke et al, 2020 ; Piccoli et al, 2018 ) and a limit of detection (LOD) of 1.8 μg mL -1 (10 nmol L -1 ) that is clinically relevant ( Sonawane and Nimse 2017 ). Interfacial conductance responses show good levels of selectivity (Figure SI-4b) and can be accurately ( ) described by the Langmuir-type isotherm plot (Figure SI-4a), with a dissociation constant entirely consistent with previous reports with a ( Baradoke et al, 2020 ).…”

Recent progress of conductive 3D-printed electrodes based upon polymers/carbon nanomaterials using a fused deposition modelling (FDM) method as emerging electrochemical sensing devices

“…The immobilised biomolecules at the electrode surfaces could be achieved either using physical adsorption, self-assembly monolayer, polymer coating or covalent immobilisation methods. 41 The targeted analytes could be cancer biomarkers, 41 viruses, 42 cardiac biomarkers, 43,44 glucose, 45 hydrogen peroxide (H 2 O 2 ), 46 foodborne pathogens 47 and heavy metal ions. 48 The common electrode substrates used to construct the immobilised biomolecule probes are GC electrode, 49 gold electrode, 50,51 screen-printed carbon electrode (SPCE) 52,53 and indium tin oxide (ITO) electrode.…”

Electrochemical sensing of blood proteins for mild traumatic brain injury (mTBI) diagnostics and prognostics: towards a point-of-care application

“…A very recent approach by Baradoke et al 169 for the first time employed a surface-confined redox active polymer ( i.e. phytic acid-doped PANI film, see Fig.…”

“…Fig.3EIS-derived capacitance-based detection of CRP, reprinted with permission from Baradoke et al169 Copyright (2020) American Chemical Society.…”