Electron Transfer Across an Antifouling Mercapto-hepta(ethylene glycol) Self-Assembled Monolayer

Abstract

Oligo(ethylene glycol) films are known to be very efficient at reducing the nonspecific adsorption of biomacromolecules on surfaces, but they often show a tendency to decrease drastically the rate of heterogeneous electron transfer at the modified surface, making them unsuitable for electrochemical biosensing. In this work, the heterogeneous electron transfer across the self-assembled monolayer of a short thiolated oligo(ethylene glycol) is investigated using four redox systems: [Fe(CN) 6 ] 3−/4− , [Ru(NH 3 ) 6 ] 3+/2+ , Fc(MeOH) 2 +/0 , and [IrCl 6 ] 2−/3− . Fast electrontransfer kinetics are evidenced in all cases except the ferri/ferrocyanide couple, for which the electron transfer is completely suppressed. Interfacial characterizations by means of spectroscopic ellipsometry, electrochemical desorption experiments, and capacity measurements indicate that the film consists of a fairly hydrated single monolayer with a surface concentration of 4.1 × 10 −10 mol cm −2 . The peculiar behavior of [Fe(CN) 6 ] 3−/4− is discussed in terms of the hydration properties of both the monolayer and the electroactive anions. Interestingly, the self-assembled monolayer exhibits the desired antifouling properties against protein adsorption, tested with bovine serum albumin, making this system a promising platform for the development of electrochemical biosensors.

Ready to Use Electrochemical Sensor Strip for Point‐of‐Care Monitoring of Serum Lithium

“…The 11‐MUA immobilized electrode revealed bigger curvature with increase in R ct by ∼35 Ω and a fairly linear tail component (Figure 2, curve 2 ), signifies the presence of SAM over screen printed gold electrode with a fairly fast charge transfer. The EIS data are consistent with previous studies SAM modified gold disc electrode for long chain thiol and thioic acid [20, 25]. Next Nyquist plot recorded after introducing DB‐14‐C‐4 over SAM modified SPAuE (sec 2.3).…”

“…Self‐assembled monolayers (SAMs) have been proposed for metal ion recognition and molecular templeting [18, 19] as well as for ligand immobilization to prevent non‐specific adsorption [20] in EC sensing through a redox probe. Flink et al .…”

Chronopotentiometry as a Sensitive Interfacial Characterisation Tool for Peptide Aptamer Monolayers

“…This corresponds to an excess surface concentration Γ t‐OEG ≈1.6×10 −10 mol cm −2 equivalent to an area of 107 Å 2 per adsorbed molecule. In view of the molecular dimensions of t‐OEG , this suggests a low coverage with flat‐lying orientation.…”

“…The strategy of using such a short sequence from the p53 protein for the recognition of Mdm2 has been already successfully implemented with plasmon based detection using nanoparticles or fluorescence and enzymatic outputs . The t‐OEG diluent is the α‐methoxy‐ω‐mercapto‐hepta(ethylene glycol), which has the well‐documented anti‐fouling properties of oligo(ethylene glycol) and is thiolated at its extremity to enable the same metal‐sulphur chemistry as for the peptide .…”

Specific Picomolar Detection of a Breast Cancer Biomarker HER‐2/neu Protein in Serum: Electrocatalytically Amplified Electroanalysis by the Aptamer/PEG‐Modified Electrode

“…In addition to their ability to prevent non-specific adsorption of proteins, the PEG-SAMs were shown to inhibit the redox reaction of the ferri-/ ferrocyanide redox couple but not electrochemical reactions of other redox molecules, such as ferrocenedimethanol or ruthenium hexamine complex. [14] That feature opens a new perspective in the biosensor research, since such SAMs not only prevent the electrode surface fouling by proteins but also allow the development of electrocatalytically amplified assays, in which signals from redox active indicators capable of binding to the targeted proteins can be amplified in the presence of ferro-/ferricyanide. Here, the redox indicator works as an electrocatalyst for the ferro-/ferricyanide transformation.…”