The importance of interfacial design for the sensitivity of a label-free electrochemical immuno-biosensor for small organic molecules

Abstract

An immuno-biosensing interface comprising a mixed layer of an oligo(ethylene glycol) (OEG) component, and an oligo(phenylethynylene) molecular wire (MW) is described. The OEG controls the interaction of proteins and electroactive interferences with the surface and the MW allows electrochemical communication to the underlying glassy carbon electrode. The layers are formed from in situ generated-aryl diazonium cations. To the distal end of the MW, a redox probe 1,1'-di(aminomethyl)ferrocene is attached followed by the surface bound epitope (the structural feature the antibody selectively recognizes) to which an antibody would bind. Association or disassociation of the antibody with the sensing interface causes a modulation of the ferrocene electrochemistry. X-ray photoelectron spectroscopy, cyclic voltammetry, and square wave voltammetry have been used to characterize the step-wise fabrication of the sensing interface. The influence of the molar ratio of the MW and OEG deposited onto the sensor interface was explored relative to the final sensor sensitivity. Five combinations of MW/OEG 1:0, 1:20, 1:50, 1:75 and 1:100 were tested on sensor sensitivity detection for a model analyte (biotin) free in solution, via a displacement assay. The ratio of 1:50 was found to give the highest sensitivity. At this ratio, good reproducibility (RSD 6.8%) and repeatability (RSD 9.6%) was achieved. This immuno-biosensor provides an intervention free immuno-biosensing platform for agriculture and biomedical samples.

Redox Active DipyrrometheneCu(II) Monolayer for Oriented Immobilization of His‐Tagged RAGE Domains – the Base of Electrochemical Biosensor for Determination of Aβ16–23′

“…In consequence, this causes the changes in the permeability of counter ions to Cu(II) redox centers. The similar phenomenon was recently described by Gooding et al These authors showed, that antibody binding to the sensing interface causes a modulation of the ferrocene electrochemistry, due to restriction of counter ions accessing the redox probe to balance the charge [41]. …”

Oriented Immobilization of His-Tagged Protein on a Redox Active Thiol Derivative of DPTA-Cu(II) Layer Deposited on a Gold Electrode—The Base of Electrochemical Biosensors

“…They discovered that the distance of ferrocene units from the electrode surface as well as the presence of different anions in the basic electrolyte strongly influence the voltammetric response of redox active monolayer. The alternation of ferrocene electrochemistry caused by antibody binding to the sensing redox active interface was described by Gooding et al [44]. The authors concluded the base of phenomenon observed was the restriction of counter ions accessing the redox sites to balance the charge.…”

DNA probe modified with 3-iron bis(dicarbollide) for electrochemical determination of DNA sequence of Avian Influenza Virus H5N1

“…Association or dissociation of the antibody at the sensing interface caused a modulation of the ferrocene electrochemistry, due to the restriction of counter ions access the redox probe (Khor et al, 2011).…”