Conventional Electrode System Research Articles

Characterising the response of novel 3D printed CNT electrodes to the virulence factor pyocyanin

• Investigation into feasibility of electrochemistry for the detection of pyocyanin. • Assessment of the use of 3D printed carbon nanotubes for pyocyanin detection. • Assessment of the use of manufactured CNT sensor for point of care devices. Electrochemical based sensors have become increasing popular within biomedical applications. Their low cost, high portability and flexibility in regard to manufacturing materials makes them ideal candidates for point of care sensors. The virulence factor pyocyanin is a useful diagnostic biomarker for the detection of Pseudomonas aeruginosa bacterium, and its phenolic functionality makes it an ideal candidate for electrochemical detection. Carbon nanotubes (CNT) exhibit a number of desirable characteristics for use as electrode materials. Not only are they cheap to acquire, they offer superb conductivity and boast high electroactive surface area. To this extent we investigated in-house 3D printed carbon nanotube electrodes for the detection of pyocyanin down to clinically relevant concentrations. Comparison was drawn against the traditional glassy carbon electrodes, with our manufactured electrodes achieving detection limits down to 1 µM, manufacturing reproducibility of 19% and a linear response across the entire therapeutic range. As such, demonstrating the feasibility to manufacture CNT sensors for point of care devices with analytical performance largely comparable to the expensive conventional electrode systems.

The Development of Fine Microgram Powder Electrode System and Its Application in the Analysis of Chalcopyrite Leaching Behavior

An electrode system to study the mechanism of fine microgram powder sulfide mineral dissolution was developed by using a relatively simple method that enables the attachment of micrograms of fine powder to a platinum plate surface. This system yields highly reproducible results and is sensitive compared with conventional electrode systems for various sulfide minerals such as pyrite, chalcopyrite, chalcocite, enargite, and tennantite. The leaching behavior of chalcopyrite was re-examined in a test of the application of this electrode system. Chalcopyrite dissolution is enhanced in specific potential regions because it is believed to be reduced to leachable chalcocite, but this result is inconclusive because it is difficult to detect the intermediate chalcocite. Powder chalcopyrite in the new powder electrode system was held at 0.45 V in the presence of copper ion and sulfuric acid media followed by an application of potential in the anodic direction. Besides the chalcopyrite oxidation peak, a small peak resulted at ∼0.55 V; this peak corresponds to reduced chalcocite, because it occurs at the same potential as the chalcocite oxidation peak.

Nanostructured Au/Ti bimetallic electrodes in selective anodic oxidation of carbohydrates

The anodic oxidation of species possessing potentially oxidisable functionalities has been studied on a non conventional electrode system based on a Ti substrate partially coated by electrodeposited Au nanoparticles. The results show that the electrocatalytic behaviour of the Au nanoparticles, in the frame of such a bimetallic system, is very different from that of pure Au. In particular, catalytic synergy between Au and Ti leads to the electro-oxidation of aldoses and aldehydes, while ketoses and monohydric alcohols result electrochemically inert. A different behaviour has been observed in the case of bulk Au surface: all the species under investigation undergo oxidation, so that no selectivity is activated. A correlation is found between the actual electroactivity and the nature of the functional group, when considered together with the chemical structure of the molecule.

Electrically Mediated Delivery of Plasmid DNA to the Skin, Using a Multielectrode Array

The easy accessibility of skin makes it an excellent target for gene transfer protocols. To take full advantage of skin as a target for gene transfer, it is important to establish an efficient and reproducible delivery system. Electroporation is a strong candidate to meet this delivery criterion. Electroporation of the skin is a simple, direct, in vivo method to deliver genes for therapy. Previously, delivery to the skin was performed by means of applicators with relatively large distances between electrodes, resulting in significant muscle stimulation and pain. These applicators also had limitations in controlling the directionality of the applied field. To resolve this issue, a system consisting of an array of electrodes that decreased the distance between them and that were independently addressable for directional control of the field was developed. This new multielectrode array (MEA) was compared with an established electrode. In a rat model, comparable reporter expression was seen after delivery with each electrode. Delivery was also evaluated in a guinea pig model to determine the potential of this approach in an animal model with skin thickness and structure similar to human skin. The results clearly showed that effective delivery was related to both the electrode and the parameters chosen. With the MEA, the muscle twitching associated with application of electric fields was notably reduced compared with conventional electrode systems. This is important, as it will facilitate the translation of electroporation-mediated gene delivery to skin for clinical use with DNA vaccines or for therapies for cancer or protein deficiencies.

Novel electrode system for electroflotation of wastewater.

Electroflotation (EF) is an attractive method in wastewater treatment. The heart of EF is the dimensionally stable oxygen evolution anode that is usually expensive. In this paper, we present a stable anode by coating IrOx-Sb2O5-SnO2 onto titanium. Accelerated life test showed that the electrochemical stability of the Ti/IrOx-Sb2O5-SnO2 anode containing only 2.5 mol % of IrOx nominally in the activated coating was even higher than that of the conventional Ti/IrOx anode. Its service life for electroflotation application is predicted to be about 20 yr. Voltammetric investigation demonstrated that the Ti/IrOx-Sb2O5-SnO2 anode could provide fast electron transfer. Moreover, the present anode was designed to be fork-like and arranged interlockingly at the same level as the cathode with a similar shape. Such an innovation in electrode configuration and arrangement allows bubbles produced at both electrodes to be dispersed into wastewater flow quickly and, therefore, enhances the effective contact between bubbles and particles, favorable for high flotation efficiency. In addition, the novel electrode system reduces the interelectrode gap to 2 mm, a spacing that is technically difficult for a conventional electrode system. This small gap results in a significant energy saving. Easy maintenance is found to be another advantage of this novel electrode system.

Development of a generic microelectrode array biosensing system

A new type of electrochemical cell has been developed for use in biosensor applications. Utilising a random array of platinum microdiscs as the working electrode, it incorporates a Ag/AgCl reference electrode and platinum auxiliary electrode into the tip of a polished glassy Teflon probe. Immobilisation of the biochemical moiety onto the surface of the probe is achieved using a mixture of polyurethane (PU) and polyethylene oxide (PEO). Enclosing the tip of the probe within a dialysis membrane completes the electrochemical cell. The hydrophilic nature of the PU–PEO mixture ensures the biochemical moiety is trapped in a stable, hydrophilic environment. The result is an all in one generic electrochemical sensor that can be used in a wide range of biosensor applications in both batch or flow injection modes. The unique features of this system are demonstrated in this paper using the glucose — glucose oxidase (GOD) system. Parameters affecting sensor performance were investigated in both batch and flow injection modes. In terms of sensitivity, reproducibility, equilibration time and linear dynamic range, the performance of the microdisc based sensing system was superior to similar macroelectrode versions. Practical detection limits (0.1 μM) were four–five orders of magnitude better for this system compared with a conventional electrode system. The advantages of using this system in flow injection mode, particularly in terms of increased linear range, were also addressed. The overall linear range of our system (0.1 μM–60 mM) is three–four orders of magnitude greater than the conventional electrode system.

Theoretical analysis of a cylindrical time-of-flight mass spectrometer with radial ion paths

Time-of-flight mass spectrometers with concentric cylindrical electrodes and ion paths directed radially inwards are potentially capable of very high sensitivity. A general expression for total ion flight time is derived for a spectrometer having four concentric electrodes which bound two accelerating regions and a drift region. The special case of negligible initial velocity is then considered and it is shown that the cylindrical geometry gives a higher order of space-time focusing than is possible with a conventional linear instrument having similarly spaced planar electrodes. The theoretical difference in resolving power amounts to a factor of at least 2–3, depending on the definition of peak width which is used. It follows that for small time-of-flight mass spectrometers a cylindrical layout offers substantially higher resolving power as well as higher sensitivity than would be possible with a more conventional electrode system.