Browsing by Author "Caygill, J. S."
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Item Open Access Current trends in explosive detection techniques(Elsevier Science B.V., Amsterdam., 2012-01-15T00:00:00Z) Caygill, J. S.; Davis, Frank; Higson, Seamus P. J.The detection of explosives and explosive-related compounds has become a heightened priority in recent years for homeland security and counter-terrorism applications. There has been a huge increase in research within this area- through both the development of new, innovative detection approaches and the improvement of existing techniques. Developments for miniaturisation, portability, field-ruggedisation and improvements in stand-off distances, selectivity and sensitivity have been necessary to develop and improve techniques. This review provides a consolidation of information relating to recent advances in explosive detection techniques without being limited to one specific research area or explosive type. The focus of this review will be towards advances in the last 5 years, with the reader being referred to earlier reviews where appropriate.Item Open Access Direct replacement of antibodies with molecularly imprinted polymer (MIP) nanoparticles in ELISA - development of a novel assay for vancomycin(American Chemical Society , 2013-09-03T00:00:00Z) Chianella, Iva; Guerreiro, Antonio R.; Moczko, Ewa; Caygill, J. S.; Piletska, Elena V.; Perez De Vargas Sansalvador, Isabel M.; Whitcombe, Michael J.; Piletsky, Sergey A.A simple and straightforward technique for coating microplate wells with molecularly imprinted polymer nanoparticles (nanoMIPs) to develop ELISA type assays is presented here for the first time. NanoMIPs were synthesized by a solid phase approach with immobilized vancomycin (template) and characterized using Biacore 3000, dynamic light scattering and electron microscopy. Immobilization, blocking and washing conditions were optimized in microplate format. The detection of vancomycin was achieved in competitive binding experiments with a HRP-vancomycin conjugate. The assay was capable of measuring vancomycin in buffer and in blood plasma within the range 0.001-70 nM with a detection limit of 0.0025 nM (2.5 pM). The sensitivity of the assay was three orders of magnitude better than a previously described ELISA based on antibodies. In these experiments nanoMIPs have shown high affinity and minimal interference from blood plasma components. Immobilized nanoMIPs were stored for 1 month at room temperature without any detrimental effects to their binding properties. The high affinity of nanoMIPs and the lack of a requirement for cold chain logistics make them an attractive alternative to traditional antibodies used in ELISAItem Open Access Electrochemical detection of TNT at cobalt phthalocyanine mediated screen-printed electrodes and application to detection of airborne vapours(Wiley-Blackwell, 2013-10-11) Caygill, J. S.; Collyer, Stuart D.; Holmes, Joanne L.; Davis, Frank; Higson, Seamus P. J.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.Item Open Access Microarray sensors for detecting airborne explosives(Cranfield University, 2011-10) Caygill, J. S.; Higson, Seamus P. J.Due to the enhanced level of national security currently required due to the possibility of terrorist attack, monitoring devices for trace levels of explosive materials are now of the upmost importance. One such method that offers a possible route towards the development of a system for the detection of such analytes is via an electrochemical regime, coupled to the use of disposable sensor technology. Within this study, the use of modified carbon screen-printed sensors for the detection and analysis of such analytes of importance has been investigated. The modification of the base carbon substrate has been undertaken in a two-fold manner; firstly the incorporation of an enhanced electroactive mediator (Cobalt Phthalocyanine) has been investigated as an aid to facilitate the signal response and secondly the use of a novel surface modification technique to produce microelectrode arrays upon the carbon has also been employed. Microelectrodes hold intrinsic advantages over planar electrodes, such as stir independence, low detection limits and increased sensitivity due to their hemispherical diffusional profile. An array of microelectrodes can retain these properties whilst including the added advantage of enhancing the current response. The integration of these two approaches, the microelectrode array coupled with the mediated electrodes, has been developed with the ultimate objective to develop an accurate and sensitive detection system for trace quantities of explosives, namely 2,4,6-trinitrotoluene (TNT). This thesis describes work focussed towards the optimisation of each of the individual components involved in the formation of a sensing device for the detection and measurement of trace levels of explosive materials. In particular, factors and techniques that may facilitate the enhanced sensitivity of the measurement device are described. At every stage, each modification step was also undertaken with a suitable redox probe, ferrocenemonocarboxylic acid to allow for a quantitative assessment to be made. The use of unmediated and mediated carbon ink has been assessed in terms of suitability as a host material for the detection of TNT, with concentrations of 400 nM being measured on these base substrates. Further to this, microelectrode arrays were then formed upon these planar carbon surfaces via insulation with poly(phenylenediamine) coating and subsequent ultrasonic ablation. These thin film microelectrode arrays (~40 nm, pore population ~7.0 x 104 cm- 2 ) were also investigated in terms of response to TNT and were seen to offer an enhanced response in terms of signal differentiation. A final stage was then applied where the microelectrode array was further modified to incorporate a conductively grown polymer from the pore areas. Within this conductive growth, an enzyme/co-factor matrix specific to TNT was deposited which was seen to further increase signal responses, although displaying a lack of sensitivity at lower concentrations. As a final step the developed sensor methodologies were then used in conjunction with an airsampling system, the Coriolis®µ cyclone, to mimic the use of the sensors in realistic environments for practical employment. The sensors were used to successfully measure TNT samples from a concentrated stock sample of 4.4 mM collected via the cyclone technique.Item Open Access Selective vancomycin detection using optical fibre long period gratings functionalised with molecularly imprinted polymer nanoparticles(Royal Society of Chemistry, 2014-02-25) Korposh, Sergiy; Chianella, Iva; Guerreiro, Antonio R.; Caygill, J. S.; Piletsky, Sergey A.; James, Stephen W.; Tatam, Ralph P.An optical fibre long period grating (LPG) sensor modified with molecularly imprinted polymer nanoparticles (nanoMIPs) for the specific detection of antibiotics is presented. The operation of the sensor is based on the measurement of changes in refractive index induced by the interaction of nanoMIPs deposited onto the cladding of the LPG with free vancomycin (VA). The binding of nanoMIPs to vancomycin was characterised by a binding constant of 4.3 ± 0.1 × 10−8 M. The lowest concentration of analyte measured by the fibre sensor was 10 nM. In addition, the sensor exhibited selectivity, as much smaller responses were obtained for high concentrations (∼700 μM) of other commonly prescribed antibiotics such as amoxicillin, bleomycin and gentamicin. In addition, the response of the sensor was characterised in a complex matrix, porcine plasma, spiked with 10 μM of VA.