Redox-tagged peptide for capacitive diagnostic assays (original) (raw)
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Label free redox capacitive biosensing
Biosensors and Bioelectronics, 2013
A surface confined redox group contributes to an interfacial charging (quantifiable by redox capacitance) that can be sensitively probed by impedance derived capacitance spectroscopy. In generating mixed molecular films comprising such redox groups, together with specific recognition elements (here antibodies), this charging signal is able to sensitively transduce the recognition and binding of specific analytes. This novel transduction method, exemplified here with C-reactive protein, an important biomarker of cardiac status and general trauma, is equally applicable to any suitably prepared interfacial combination of redox reporter and receptor. The assays are label free, ultrasensitive, highly specific and accompanied by a good linear range.
Nanostructured functional peptide films and their application in C-reactive protein immunosensors
Bioelectrochemistry, 2021
Peptides with an active redox molecule are incorporated into nanostructured films for electrochemical biosensors with stable and controllable physicochemical properties. In this study, we synthesized three ferrocene (Fc)-containing peptides with the sequence Fc-Glu-(Ala) n-Cys-NH 2 , which could form selfassembled monolayers on gold and be attached to antibodies. The peptide with two alanines (n = 2) yielded the immunosensor with the highest performance in detecting C-reactive protein (CRP), a biomarker of inflammation. Using electrochemical impedance-derived capacitive spectroscopy, the limit of detection was 240 pM with a dynamic range that included clinically relevant CRP concentrations. With a combination of electrochemical methods and polarization-modulated infrared reflection-absorption spectroscopy, we identified the chemical groups involved in the antibody-CRP interaction, and were able to relate the highest performance for the peptide with n = 2 to chain length and efficient packing in the organized films. These strategies to design peptides and methods to fabricate the immunosensors are generic, and can be applied to other types of biosensors, including in low cost platforms for point-ofcare diagnostics.
An optimised electrochemical biosensor for the label-free detection of C-reactive protein in blood
Biosensors and Bioelectronics, 2013
C-reactive protein (CRP) is an acute phase protein whose levels are increased in many disorders. There exists, in particular, a great deal of interest in the correlation between blood serum levels and the severity of risk for cardiovascular disease. A sensitive, label-free, non-amplified and reusable electrochemical impedimetric biosensor for the detection of CRP in blood serum was developed herein based on controlled and coverage optimised antibody immobilization on standard polycrystalline gold electrodes. Charge transfer resistance changes were highly target specific, linear with log CRP concentration across a 0.5-50nM range and associated with a limit of detection of 176pM. Significantly, the detection limits are better than those of current CRP clinical methods and the assays are potentially cheap, relatively automated, reusable, multiplexed and highly portable. The generated interfaces were capable not only of comfortably quantifying CRP across a clinically relevant range of concentrations but also of doing this in whole blood serum with interfaces that were, subsequently, reusable. The importance of optimising receptor layer resistance in maximising assay sensitivity is also detailed.
Redox Capacitive Assaying of C-Reactive Protein at a Peptide Supported Aptamer Interface
Analytical chemistry, 2018
Electrochemical immunosensors offer much in the potential translation of a lab based sensing capability to a useful "real world" platform. In previous work we have introduced an impedance-derived electrochemical capacitance spectroscopic analysis as supportive of a reagentless means of reporting on analyte target capture at suitably prepared mixed-component redox-active, antibody-modified interfaces. Herein we directly integrate receptive aptamers into a redox charging peptide support in enabling a label-free low picomolar analytical assay for C-reactive protein with a sensitivity that significantly exceeds that attainable with an analogous antibody interface.
Comparing label free electrochemical impedimetric and capacitive biosensing architectures
Biosensors & bioelectronics, 2014
The transducer faradaic signals of molecularly receptive interfaces associated with specific target binding can be sensitively monitored by electrochemical impedance and/or capacitance spectroscopies. A comparative evaluation of both impedimetric (associated with charge transfer resistance) and capacitive (associated with faradaic density of states) approaches was undertaken using C-reactive protein (CRP) antigen and antibody interaction as biomolecular binding model. Aiming at constructing redox free (impedimetric) and redox tethered receptive (capacitive) interfaces engineered by self-assembly monolayer, CRP sensitivity and limit of detections were comparatively assessed regarding biosensor capabilities. Binding affinity constant between CRP and anti-CRP interfacial receptor sites were additionally evaluated by the Langmuir adsorption model. Both the impedimetric and capacitive approaches reported similar values of experimental analytical parameters albeit the latter was found to ...
Optimized diagnostic assays based on redox tagged bio-receptive interfaces
Analytical chemistry, 2015
Among the numerous label free biomarker assaying methodologies available, Electrochemical Impedance based Capacitance Spectroscopy (ECS) based upon mapping the interfacial charging elements of an additionally receptive interface, has been shown to be a convenient and highly sensitive mode of transduction and one which, additionally, requires no pre-doping of analytical solution. We present, herein, a data acquisition methodology based on immittance function analysis. Ultimately this enables both a maximization of assay sensitivity and a reduction in assay acquisition time by an order of magnitude.
Label-free Capacitive Diagnostics: Exploiting Local Redox Probe State Occupancy
Analytical Chemistry, 2014
An electrode surface confined redox group contributes to a substantial potential-dependent interfacial charging that can be sensitively probed and frequency-resolved by impedance-derived capacitance spectroscopy. In utilizing the sensitivity of this charging fingerprint to redox group environment, one can seek to generate derived sensory configurations. Exemplified here through the generation of mixed molecular films comprising ferrocene and antibody receptors to two clinically important targets, the label-free methodology is able to report on human prostatic acid phosphatase (PAP), a tumor marker, with a limit of detection of 11 pM and C-reactive protein with a limit of detection of 28 pM. Both assays exhibit linear ranges encompassing those of clinical value.
Frontiers in Chemistry, 2021
The detection and monitoring of biological markers as disease indicators in a simple manner is a subject of international interest. In this work, we report two simple and sensitive label-free impedimetric immunoassays for the detection of C-reactive protein (CRP). The gold electrode modified with boronic acid–terminated self-assembled monolayers afforded oriented immobilization of capture glycosylated antibody (antihuman CRP monoclonal antibody, mAb). This antibody-modified surface was able to capture human CRP protein, and the impedance signal showed linear dependence with CRP concentration. We confirmed the immobilization of anti-CRP mAb using surface sensitive X-ray photoelectron spectroscopy (XPS) and electrochemical impedance. The oriented covalent immobilization of mAb was achieved using glycosylated Fc (fragment, crystallizable) region specific to boronic acid. The direct immunoassay exhibited a linear curve for concentration range up to 100 ng ml−1. The limit of detection (L...
Sensors, 2020
Nowadays, electrochemical biosensors are reliable analytical tools to determine a broad range of molecular analytes because of their simplicity, affordable cost, and compatibility with multiplexed and point-of-care strategies. There is an increasing demand to improve their sensitivity and selectivity, but also to provide electrochemical biosensors with important attributes such as near real-time and continuous monitoring in complex or denaturing media, or in vivo with minimal intervention to make them even more attractive and suitable for getting into the real world. Modification of biosensors surfaces with antibiofouling reagents, smart coupling with nanomaterials, and the advances experienced by folded-based biosensors have endowed bioelectroanalytical platforms with one or more of such attributes. With this background in mind, this review aims to give an updated and general overview of these technologies as well as to discuss the remarkable achievements arising from the developme...
Analytica Chimica Acta, 2009
A possibility of using a range of dc and ac electrochemical techniques to probe associative interactions of Creactive protein (CRP) with CRP antibody (aCRP) immobilized on a gold electrode surface was investigated. It was demonstrated that the investigated electrochemical techniques can be used efficiently to probe these interactions over a wide CRP concentration range, from 1.15 × 10 −5 to 1.15 mg L −1. The measured sensitivity of the techniques is in the following decreasing order: differential pulse voltammetry, chargetransfer resistance obtained from electrochemical impedance spectroscopy (EIS), cyclic voltammetry, chronoamperometry, and double-layer capacitance deduced from EIS measurements which gave the poorest sensitivity. Measurements of kinetic parameters demonstrated that the associative interactions of CRP with the immobilized aCRP reached quasi-equilibrium after 20-30 min. The kinetics of these interactions was modeled successfully using a two-step kinetic model. In this model, the first step represents reversible CRP-aCRP associative-dissociative interactions, while the second step represents the irreversible transformation of the bound CRP into a thermodynamically stable configuration. It was demonstrated that the thermodynamically stable configuration of CRP starts prevailing after 7 min of interaction of CRP with the immobilized aCRP.