Stepwise synthesis of Gly−Gly−His on gold surfaces modified with mixed self-assembled monolayers

Peptide-modified electrode surfaces have been shown to have excellent recognition properties for metal ions. An efficient method of screening a potential peptide for its selectivity for a given metal would involve the synthesis of the peptide directly on the electrode surface. This paper outlines a procedure in which the tripeptide Gly−Gly−His was synthesized one amino acid at a time on a gold surface modified with a self-assembled monolayer of the mixed alkanethiolates 3-mercaptopropionic acid (MPA) and 3-mercaptopropane (MP). Electrochemistry and high-resolution mass spectrometry were used to elucidate the structure of the adsorbed species and follow the synthesis. The amino acids can be attached only to MPA, but the presence of a diluting unreactive molecule of MP reduces steric crowding about the reaction center. The maximum coverage of synthesized tripeptide occurs at a ratio of MPA/MP of 1:1.

General approach for electrochemical functionalization of glassy carbon surface by in situ generation of diazonium ion under acidic and non-acidic condition with a cascade protocol

Immobilization of catechol derivatives on GC electrode surfaces can be performed by in situ generation and reduction of nitrocatechol. We present the oxidative nitration of catechol in the presence of nitrous acid followed by electrochemically reduction of the generated nitro aromatic group to the corresponding amine group and its conversion to diazonium cation at the electrode surface to yield a surface covalently modified with catechol. In this manner, some derivatives of catechol can be immobilized on the electrode surface. Whole of the process is carried out in Triethylammonium acetate ionic liquid as an inert and neutral medium (pH∼7.0). Surface coverage can be easily controlled by the applied potential, time and concentration of catechol. After modification, the electrochemical features of modified surface have been studied. Also modified GC electrode exhibited remarkable catalytic activity in the oxidation of NADH. The catalytic currents were proportional to the concentration of NADH over the range 0.01-0.80 mM. This condition can be used for modification of GC surfaces by various aromatic molecules for different application such as design of sensors and biosensors. © 2014 Elsevier Ltd. All rights reserved.

One step multifunctional micropatterning of surfaces using asymmetric glow discharge plasma polymerization

Micropatterning of surfaces with varying chemical, physical and topographical properties usually requires a number of fabrication steps. Herein, we describe a micropatterning technique based on plasma enhanced chemical vapour deposition (PECVD) that deposits both protein resistant and protein repellent surface chemistries in a single step. The resulting multifunctional, selective surface chemistries are capable of spatially controlled protein adhesion, geometric confinement of cells and the site specific confinement of enzyme mediated peptide self-assembly.

Azide photochemistry for facile modification of graphitic surfaces : preparation of DNA-coated carbon nanotubes for biosensing

A facile, two-step method for chemically attaching single-stranded DNA to graphitic surfaces, represented here by carbon nanotubes, is reported. In the first step, an azide-containing compound, N-5-azido-nitrobenzoyloxy succinimide (ANB-NOS), is used to form photo-adducts on the graphitic surfaces in a solid-state photochemical reaction, resulting in active ester groups being oriented for the subsequent reactions. In the second step, pre-synthesized DNA strands bearing a terminal amine group are coupled in an aqueous solution with the active esters on the photo-adducts. The versatility of the method is demonstrated by attaching pre-synthesized DNA to surfaces of carbon nanotubes in two platforms—as vertically-aligned multi-walled carbon nanotubes on a solid support and as tangled single-walled carbon nanotubes in mats. The reaction products at various stages were characterized by x-ray photoelectron spectroscopy. Two different assays were used to check that the DNA strands attached to the carbon nanotubes were able to bind their partner strands with complementary base sequences. The first assay, using partner DNA strands tethered to gold nanoparticles, enabled the sites of DNA attachment to the carbon nanotubes to be identified in TEM images. The second assay, using radioactively labelled partner DNA strands, quantified the density of functional DNA strands attached to the carbon nanotubes. The diversity of potential applications for these DNA-modified carbon-nanotube platforms is exemplified here by the successful use of a DNA-modified single-walled carbon-nanotube mat as an electrode for the specific detection of metal ions.

Molecularly engineered graphene surfaces for sensing applications: A review.

Graphene is scientifically and commercially important because of its unique molecular structure which is monoatomic in thickness, rigorously two-dimensional and highly conjugated. Consequently, graphene exhibits exceptional electrical, optical, thermal and mechanical properties. Herein, we critically discuss the surface modification of graphene, the specific advantages that graphene-based materials can provide over other materials in sensor research and their related chemical and electrochemical properties. Furthermore, we describe the latest developments in the use of these materials for sensing technology, including chemical sensors and biosensors and their applications in security, environmental safety and diseases detection and diagnosis.

A novel graphene nanodots inlaid porous gold electrode for electrochemically controlled drug release

A uniform graphene nanodots inlaid porous gold electrode was prepared via ion beam sputtering deposition (IBSD) and mild corrosion chemistry. HRTEM, SEM, AFM and XPS analyses revealed the successful fabrication of graphene nanodots inlaid porous gold electrode. The as-prepared porous electrode was used as π-orbital-rich drug loading platform to fabricate an electrochemically controlled drug release system with high performance. π-orbital-rich drugs with amino mioety, like doxorubicin (DOX) and tetracycline (TC), were loaded into the graphene nanodots inlaid porous gold electrode via non-covalent π-π stacking interaction. The amino groups in DOX and TC can be easily protonated at acidic medium to become positively-charged NH3(+), which allow these drug molecules to be desorbed from the porous electrode surface via electrostatic repulsion when positive potential is applied at the electrode. The drug loading and release experiment indicated that this graphene nanodots inlaid porous gold electrode can be used to conveniently and efficiently control the drug release electrochemically. Not only did our work provide a benign method to electrochemically controlled drug release via electrostatic repulsion process, it also enlighten the promising practical applications of micro electrode as a drug carrier for precisely and efficiently controlled drug release via embedding in the body.

Visualising dynamic passivation and localised corrosion processes occurring on buried steel surfaces under the effect of anodic transients

A new method of visualising dynamically changing electrode processes has been demonstrated by mapping localised corrosion processes occurring on buried steel surfaces under the effect of anodic transients. Dynamically shifting external electrical interferences such as anodic transients are known to affect the efficiency of cathodic protection (CP) of underground pipelines; however unfortunately conventional techniques including electrochemical methods have difficulties in measuring such effects. In this paper we report that the wire beam electrode has necessary temporal and spatial resolutions required for measuring and visualising the dynamic effects of anodic transients on CP, passivation and localised corrosion processes occurring on buried steel surfaces. For the first time a critical anodic transient duration has been observed and explained as the incubation period for the breakdown of passivity and the initiation of localised corrosion.