Séamus P. J. Higson

We describe the use of cobalt phthalocyanine as a mediator to improve the sensitivity for the electrochemical detection of TNT. Commercial screen‐printed electrodes containing cobalt phthalocyanine were employed for determination of TNT. Improved sensitivities compared to screen‐printed carbon electrodes without phthalocyanine were observed, current response for cyclic voltammetric measurements at modified electrodes being at least double that of unmodified electrodes. A synergistic effect between oxygen and TNT reduction was also observed. Correlation between TNT concentrations and sensor output was observed between 0–200 µM TNT. Initial proof‐of‐concept experiments combining electrochemical determinations, with the use of an air‐sampling cyclone, are also reported.

Due to the heightened level of national security currently prevalent due to the possibility of terrorist incidents, highly portable, miniaturised and sensitive monitoring devices for trace levels of injurious materials, such as explosives are now of the upmost importance. One method that offers a possible route for the development of a detection system for such species is via an electrochemical regime, coupled to the use of disposable sensor technology. Within this study, the use of carbon screen-printed sensors for the detection and analysis of the classical explosive trinitrotoluene (TNT) and the related dinitrotoluene (DNT) is described, with the eventual objective to develop an inexpensive, accurate and sensitive detection system for trace quantities of explosives in field settings. Commercially available screen-printed carbon sensors have been used as the base platform for this investigation and the electrochemistry of both TNT and DNT studied at these surfaces. Two reductive peaks and one oxidative peak were observed for both analytes. The best linear fits and sensitivities were obtained using the reductive peak at −0.72 V vs. Ag/AgCl. A linear range from 1 to 200 μM could be obtained for TNT and DNT in pH 7.0 phosphate buffer with limits of detection as low as 0.4 μM (TNT) and 0.7 μM (DNT). A second system which utilised the addition of the enzyme, nitroreductase, and the coenzyme, NADPH, into the solution matrix prior to electrochemical interrogations with screen-printed carbon electrodes was found to increase the resulting signal magnitude at the oxidation peak at +0.3 V, improving the performance of the sensor at these values.

We developed label less immunosensors for the stroke marker protein S-100[β], utilizing polyaniline electrode microarrays as substrates to immobilize biotinylated S-100[β] antibodies using classical affinity approaches. The AC impedance studies, before and after exposure to solutions of S-100[β], showed increasing antigen concentration caused increases in the real component of the impedance. Subtracting specific and non-specific antibody responses eliminated non-specific adsorption effects. Linear impedimetric responses toward S-100[β] in buffer solutions over a concentration range of 0–50 pg ml⁻¹ were observed. The limit of detection of the immunosensor was 1 pg ml⁻¹ S-100[β], discrimination was possible at 10 pg ml⁻¹.

The development, manufacture, modification and subsequent utilisation of sonochemically-formed microelectrode arrays is described for a range of applications. Initial fabrication of the sensing platform utilises ultrasonic ablation of electrochemically insulating polymers deposited upon conductive carbon substrates, forming an array of up to 70,000 microelectrode pores cm^–2. Electrochemical and optical analyses using these arrays, their enhanced signal response and stir-independence area are all discussed. The growth of conducting polymeric “mushroom” protrusion arrays with entrapped biological entities, thereby forming biosensors is detailed. The simplicity and inexpensiveness of this approach, lending itself ideally to mass fabrication coupled with unrivalled sensitivity and stir independence makes commercial viability of this process a reality. Application of microelectrode arrays as functional components within sensors include devices for detection of chlorine, glucose, ethanol and pesticides. Immunosensors based on microelectrode arrays are described within this monograph for antigens associated with prostate cancer and transient ischemic attacks (strokes).

Pediatric Research publishes original papers, invited reviews, and commentaries on the etiologies of diseases of children and disorders of development, extending from molecular biology to epidemiology. Use of model organisms and in vitro techniques relevant to developmental biology and medicine are acceptable, as are translational human studies.