Staff publications - Cranfield University at Silsoe
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Browsing Staff publications - Cranfield University at Silsoe by Publisher "Elsevier Science B.V., Amsterdam."
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Item Open Access Biotin–specific synthetic receptors prepared using molecular imprinti(Elsevier Science B.V., Amsterdam., 2004-02-16T00:00:00Z) Piletska, Elena V.; Piletsky, Sergey A.; Karim, K.; Terpetschnig, E.; Turner, Anthony P. F.The composition of new molecularly imprinted polymers (MIPs) specific for biotin was optimised using molecular modelling software. Three functional monomers: methacrylic acid (MAA), 2-(trifluoromethyl)acrylic acid (TFAA) and 2-acrylamido- 2-methyl-propanesulfonic acid (AMPSA), which demonstrated the highest binding scores with biotin, were tested on their ability to generate specific binding sites. The imprinted polymers were photografted to the surface of polystyrene microspheres in water. The affinity of the synthetic "receptor" sites was evaluated in binding experiments using horseradish peroxidase-labelled biotin. A good correlation was found between the modelling results and the performance of the materials in the template rebinding study. The dissociation constants for all MIPs were 1.4-16.8 nM, which is sufficient for most analytical applications where biotin is used as a label.Item Open Access Custom synthesis of molecular imprinted polymers for biotechnological application: preparation of a polymer selective for tylosin(Elsevier Science B.V., Amsterdam., 2004-02-16T00:00:00Z) Piletsky, Sergey A.; Piletska, Elena V.; Karim, K.; Foster, G.; Legge, C.; Turner, Anthony P. F.A molecularly imprinted polymer (MIP) selective for tylosin was designed and synthesised using a computational method (MIP “dialling”). In re-binding experiments the MIP demonstrated high affinity for tylosin in aqueous solutions and in organic solvents. The synthesised polymer was tested for re-binding with the template and related metabolites such as tylactone, narbomycin and picromycin. The HPLC analysis showed that the computationally designed polymer is specific and capable of separating the template from its structural analogues. The MIP was capable of recovering tylosin from broth samples. The polymer capacity for tylosin was estimated as 6.4 mg/g for MIP, which was suitable for practical application and tylosin recovery from broth samples. Among the advantages of this was the possibility to adsorb tylosin from a complex media with easy removal of oils and other impurities which are present in significant quantities, which can create problems for its chromatographic purification procedure. The MIP “dialling” procedure can have a general significance for the fast preparation of specific adsorbents for biotechnological appliItem Open Access Development and application of a soil classification-based conceptual catchment- scale hydrological model(Elsevier Science B.V., Amsterdam., 2005-10-01T00:00:00Z) Marechal, David; Holman, Ian P.A conceptual, continuous, daily, semi distributed catchment-scale rainfall- runoff model that has the potential to be ultimately used in ungauged catchments is described. The Catchment Resources and Soil Hydrology (CRASH) model is developed from the basis that the transformation of rainfall into simulated river discharge can be parameterised using pre-existing national datasets of soil, land use and weather; and that the spatial variability in soil properties and land use are important to the hydrological response of a catchment and should be incorporated into the catchment representation. Both infiltration- excess and saturation-excess runoff mechanisms are simulated, with water movement through each soil layer simulated using a capacitance approach limited according to layer physical properties. The hydrological linkage between the response unit and catchment is parameterised using the existing national Hydrology of Soil Types (HOST) classification. The HOST classification groups all UK soil types into one of 29 hydrological classes for which nationally calibrated values of Base Flow Index and Standard Percentage Runoff are provided. CRASH has been calibrated and validated for three catchments in England with contrasting soil characteristics and meteorological conditions. The model was successful at simulating time series and flow duration curves in all catchments during the calibration and validation periods. The next development stage will be to test CRASH for a large number of catchments covering a wider range of soils, land uses and meteorological conditions, in order to derive a set of regionalised model parameters based upon the HOST classification. The successful cross-scale linkage between water movement through the response unit and the catchment-scale hydrological response using the HOST classification, which incorporates the scale effects between plot and catchment, suggests that such national soil hydrological classifications may provide a sound and consistent framework for hydrological modelling in both gauged and ungauged catchments which should be extended to other regions.Item Open Access The electrochemistry of the ferri/ferrocyanide couple at a calix [4]resorcinarenetetrathiol-modified gold electrode as a study of novel electrode modifying coatings for use within electro-analytical sensors(Elsevier Science B.V., Amsterdam., 2003-06-05T00:00:00Z) Collyer, Stuart D.; Davis, Frank; Lucke, Andrew; Stirling, Charles J. M.; Higson, Seamus P. J.The electrochemistry of the ferri/ferrocyanide redox couple has been studied at Au electrodes modified with calix[4]resorcinarenetetrathiol. Cyclic voltammetry in Fe(CN)63- solutions yields three separate pairs of faradaic peaks. Evidence is given for these redox couples corresponding to the reduction of Fe(CN)63- and the subsequent re-oxidation of Fe(CN)64- in three differing steric arrangements. One pair of peaks suggest that when the Fe(CN)63- ion resides within the calix [4]resorcinarene bowl, electron transport is facilitated by the calix [4]resorcinarene acting as a charge transfer mediator; in this arrangement the activation energy is found to be lowered by ~24kJmol-1. Another pair of peaks is thought to correspond to the reduction of Fe(CN)63- as it approaches the Au electrode by packing itself in-between adjacent calix[4]resorcinarene molecules. The third pair of redox peaks is attributed to the reduction and subsequent re- oxidation of Fe(CN)63-/Fe(CN)64- when the ion resides above a saturated calix [4]resorcinarene coating; in this case the activation energy was raised by ~45kJmol-1. FTIR spectroscopy of calix[4]resorcinarene-coated Au electrodes and calix[4]resorcinarene-coated Au electrodes exposed to Fe(CN)63- lends further support to this argument, by demonstrating that the Fe(CN)63- ion resides within at least two and possibly three differing environments. Calix[4]resorcinarene modified electrodes previously exposed to ferricyanide lose the calix [4]resorcinarene coating together with a surface layer of gold when subsequently scanned in a phosphate buffer. It therefore appears that the calix [4]resorcinarene/Fe(CN)63- association is stronger than the Au binding to the underlying glass material.Item Open Access Immunosensor for okadaic acid using quartz crystal microbalance(Elsevier Science B.V., Amsterdam., 2002-10-23T00:00:00Z) Tang, Alice X. J.; Pravda, Miloslav; Guilbault, George G.; Piletsky, Sergey A.; Turner, Anthony P. F.An immunosensor for the determination of okadaic acid (OA) using a quartz crystal microbalance (QCM) was developed and optimised in standard solutions. Several coupling techniques, protein A, protein G and polyethylenimine (PEI) with glutaraldehyde (GA) cross-linking, were investigated for the determination of okadaic acid and a very good result was obtained with PEI coupling. With the PEI coupling method, the optimisation of incubation time for the activation of PEI on the crystal surface using GA, the effect of the dilution factor of OA-BSA conjugate and the amount of antibody on crystal frequency were studied. Different molar ratios (4:1, 14:1, 30:1) of OA to bovine serum albumin (BSA) for the conjugation were examined and the results using ELISA and a QCM showed that a ratio of 14:1 was slightly better than the other two. The strong attachment of the cross-linked complex to the gold surface resulted in an excellent storage lifetime of 38 days. However, the detection limit (1.9 µg/ml) and the sensitivity of the sensor were not satisfactory. Significant improvement of the performance of the device was obtained by incorporating an antibody-BSA hydrogel. Initial results showed that the minimum amount of analyte detectable and the sensitivity of the device were improved by 524 and 80 fold, respectivelyItem Open Access Labeless AC impedimetric antibody-based sensors with pg ml-1 sensitivities for point-of-care biomedical applications.(Elsevier Science B.V., Amsterdam., 2009-01-01T00:00:00Z) Barton, Andrew C.; Collyer, Stuart D.; Davis, Frank; Garifallou, Goulielmos-Zois; Tsekenis, Georgios; Tully, Elizabeth; O'Kennedy, Richard; Gibson, Tim; Millner, Paul A.; Higson, Seamus P. J.This paper describes the development and characterisation of labeless immunosensors for (a) the cardiac drug digoxin and (b) bovine serum albumin (BSA). Commercial screen-printed carbon electrodes were used as the basis for the sensors. Two methods were used to immobilise antibodies at the electrode surface. Aniline was electropolymerised onto these electrodes to form a thin planar film of conductive polyaniline; the polyaniline film was then utilised as a substrate to immobilise biotinylated anti-digoxin using a classical avidin- biotin affinity approach. As an alternative approach, poly(1,2-diaminobenzene) was electrodeposited onto the carbon electrodes and this modified surface was then sonochemically ablated to form an array of micropores. A second electropolymerisation step was then used to co-deposit conductive polyaniline along with antibodies for BSA within these pores to produce a microarray of polyaniline protrusions with diameters of several μm, containing entrapped anti- BSAItem Open Access Labeless and reversible immunosensor assay based upon an electrochemical current-transient protocol(Elsevier Science B.V., Amsterdam., 2003-10-24T00:00:00Z) Grant, Sarah; Davis, Frank; Pritchard, Jeanette A.; Law, Karen A.; Higson, Seamus P. J.; Gibson, Timothy D.A novel labeless and reversible immunoassay based upon an electrochemical current-transient protocol is reported which offers many advantages in comparison to classical immuno-biochemical analyses in terms of simplicity, speed of response, reusability and possibility of multiple determinations. Conducting polypyrrole films containing antibodies against 1) Bovine Serum Albumin (BSA) and 2) Digoxin were deposited on the surface of platinum electrodes to produce conductive affinity matrices having clearly defined binding characteristics. The deposition process has been investigated using 125I labelled anti-digoxin to determine optimal fabrication protocols. Antibody integrity and activity, together with non-specific binding of antigen on the conducting matrix have also been investigated using tritiated digoxin to probe polypyrrole/anti-digoxin films. Amperometric responses to digoxin were recorded in flow conditions using these films, but the technique was limited in use mainly due to baseline instability. Anti-BSA - polypyrrole matrices were investigated in more detail in both flow and quiescent conditions. No observable response was found in flow conditions, however under quiescent conditions (in non-stirred batch cell), anti-BSA – polypyrrole films have been demonstrated to function as novel quantitative chronoamperometric immuno-biosensors when interrogated using a pulsed potential waveform. The behaviour of the electrodes showed that the antibody/antigen binding and/or interaction process underlying the response observed was reversible in nature, indicating that the electrodes could be used for multiple sensing protocols. Calibration profiles for BSA demonstrated linearity for a concentration range of 0-50 ppm but tended towards a plateau at higher concentrations. Factors relating to replicate sensor production, sample measurement and reproducibility are discusseItem Open Access Langmuir and LB properties of two calix[4]resorcinarenes: Interactions with various analytes(Elsevier Science B.V., Amsterdam., 2008-05-15T00:00:00Z) Sugden, Mark W.; Richardson, Tim H.; Davis, Frank; Higson, Seamus P. J.; Faul, Charl F. J.The ability of calixarene-based molecules to interact with amino acids has been the basis of many studies. The Langmuir and LB properties of two calix [4]resorcinarenes have been investigated. The properties of the layer formed at the air–water interface were studied by surface pressure–area isotherms. LB deposition onto glass substrates has shown that multilayer assemblies can be built up. The UV–vis spectra of resulting LB films have been recorded, indicating that the compounds are coloured as a result of intra-molecular charge transfer bands. The sensitivity of the surface pressure–area isotherms has been investigated in relation to the exposure to various analytes delivered from the subphase (i.e. amino acids). Furthermore, exposure of the LB films to a wide range of vapours (e.g. amines, alcohols, thiols) has led to modified UV–viItem Open Access A new reactive polymer suitable for covalent immobilisation and monitoring of primary amines(Elsevier Science B.V., Amsterdam., 2001-04-01T00:00:00Z) Piletska, Elena V.; Piletsky, Sergey A.; Subrahmanyam, S.; Turner, Anthony P. F.A new polymer able to react with primary amines was synthesised from allyl mercaptan, o-phtalic dialdehyde and ethylene glycol dimethacrylate by radical polymerisation. Reactive thioacetale formed by allyl mercaptan and dialdehyde can bind primary amino groups without additional pre-activation forming fluorescent isoindole complex. It gives a great opportunity to monitor binding and loading of the amino compounds on the reactive surface. The reactive polymer is found to be an effective matrix for immobilisation of the proteins and other amino containing compounds in affinity chromatography and could be used for their detection in solution.Item Open Access Optical and AFM study of electrostatically assembled films of CdS and ZnS colloid nanoparticles.(Elsevier Science B.V., Amsterdam., 2008-05-30T00:00:00Z) Suryajaya, S.; Nabok, Alexei; Davis, Frank; Hassan, A.; Higson, Seamus P. J.; Evans-Freeman, J.CdS and ZnS semiconducting colloid nanoparticles coated with the organic shell, containing either SO3− or NH2+ groups, were prepared using the aqueous phase synthesis. The multilayer films of CdS (or ZnS) were deposited onto glass, quartz and silicon substrates using the technique of electrostatic self- assembly. The films produced were characterized with UV–vis spectroscopy, spectroscopic ellipsometry and atomic force microscopy. A substantial blue shift of the main absorption band with respect to the bulk materials was found for both CdS and ZnS films. The Efros equation in the effective mass approximation (EMA) theoretical model allowed the evaluation of the nanoparticle radius of 1.8 nm, which corresponds well to the ellipsometry results. AFM shows the formation of larger aggregates of nanoparticles on solid surfaItem Open Access Preformed antifungal compounds in strawberry fruit and flower tissues(Elsevier Science B.V., Amsterdam., 2004-02-01T00:00:00Z) Terry, Leon A; Joyce, Daryl C.; Adikaram, Nimal K. B.; Khambay, Bhupinder P. S.Antifungal activity against the pathogen, Botrytis cinerea, and a bioassay organism, Cladosporium cladosporioides, declined with advancing strawberry fruit maturity as shown by thin layer chromatography (TLC) bioassays. Preformed antifungal activity was also present in flower tissue. The fall in fruit antifungal compounds was correlated with a decline in natural disease resistance (NDR) against B. cinerea in-planta. Crude extracts of green stage I fruit (7 days after anthesis) contained at least two preformed antifungal compounds (Rf = 0.44 and 0.37) that were not present in white and red stage fruit. These compounds were shown with TLC reagent sprays to be neither phenolics nor alkaloids. Positive reactions to Ehrlich’s reagent suggested that Rf = 0.37 was a terpene. Most antifungal activity was found in the achenes of green stage I fruit. However, antifungal activity was found in all tissue types (viz. pith, cortex, epidermis) of green stage I fruit. TLC bioassays revealed that all fruit stages yielded antifungal activity at the origin (Rf = 0.00). The approximate area of fungal inhibition at the origin in green stage 1 fruit extracts was 1.87-fold and 1.73-fold greater than in white and red stages, respectively. TLC reagent sprays showed that the antifungal compound(s) at origin included phenolics. This observation is consistent with previous reports that phenolic compounds in strawberry fruit are inhibitory to B. cinereItem Open Access Sonochemically fabricated microelectrode arrays for biosensors offering widespread applicability. Part I(Elsevier Science B.V., Amsterdam., 2004-09-15T00:00:00Z) Barton, Andrew C.; Collyer, Stuart D.; Davis, Frank; Gornall, Davinia D.; Law, Karen A.; Lawrence, Emma C. D.; Mills, Daniel W.; Myler, Suzy; Pritchard, Jeanette A.; Thompson, Mark; Higson, Seamus P. J.A novel and patented procedure is described for the sonochemical fabrication of a new class of microelectrode array based sensor with electrode element populations of up to 2 x 105 cm-2. For some years it has been accepted that microelectrode arrays offer an attractive route for lowering minimum limits of detection and imparting stir (convectional mass transport) independence to sensor responses; despite this no commercial biosensors, to date, have employed microelectrode arrays, largely due to the cost of conventional fabrication routes that have not proved commercially viable for disposable devices. Biosensors formed by our sonochemical approach offer unrivalled sensitivity and impart stir independence to sensor responses. This format lends itself for mass fabrication due to the simplicity and inexpensiveness of the approach; in the first instance impedimetric and amperometric sensors are reported for glucose as model systems. Sensors already developed for ethanol, oxalate and a number of pesticide determinations will be reported in subsequent publications.Item Open Access Sonochemically fabricated microelectrode arrays for biosensors. Part II. Modification with a polysiloxane coating(Elsevier Science B.V., Amsterdam., 2004-09-15T00:00:00Z) Myler, Suzy; Davis, Frank; Collyer, Stuart D.; Higson, Seamus P. J.A polymer modified sonochemically fabricated glucose oxidase microelectrode array with microelectrode population densities of up to 2.5 x 105 microelectrodes cm-2 is reported. These microelectrode sensors were formed by first depositing an insulating film on commercial screen printed electrodes which was subsequently sonicated to form cavities of regular sizes in the film. Electropolymerisation of aniline at the microelectrode cavities formed polyaniline protrusions containing entrapped glucose oxidase. Chemical deposition of polysiloxane from dichlorodimethysilane was used to deposit a thin protective and diffusion mass transport controlling coating over the electrodes. The physical and electrochemical properties of these films were studied. The performance of the final glucose oxidase based microelectrode sensor array is reported.Item Open Access The study of genomic DNA adsorption and subsequent interactions using total internal reflection ellipsometry.(Elsevier Science B.V., Amsterdam., 2007-10-31T00:00:00Z) Nabok, Alexei; Tsargorodskaya, Anna; Davis, Frank; Higson, Seamus P. J.The adsorption of genomic DNA and subsequent interactions between adsorbed and solvated DNA was studied using a novel sensitive optical method of total internal reflection ellipsometry (TIRE), which combines spectroscopic ellipsometry with surface plasmon resonance (SPR). Single strands of DNA of two species of fish (herring and salmon) were electrostatically adsorbed on top of polyethylenimine films deposited upon gold coated glass slides. The ellipsometric spectra were recorded and data fitting utilized to extract optical parameters (thickness and refractive index) of adsorbed DNA layers. The further adsorption of single stranded DNA from an identical source, i.e. herring ss-DNA on herring ss-DNA or salmon ss-DNA on salmon ss-DNA, on the surface was observed to give rise to substantial film thickness increases at the surface of about 20–21 nm. Conversely adsorption of DNA from alternate species, i.e. salmon ss- DNA on herring ss-DNA or herring ss-DNA on salmon ss-DNA, yielded much smaller changes in thickness of 3–5 nm. AFM studies of the surface roughness of adsorbed layers were in line with the TIRE dItem Open Access Substitution of antibodies and receptors with molecularly imprinted polymers in enzyme-linked and fluorescent assays(Elsevier Science B.V., Amsterdam., 2001-12-31T00:00:00Z) Piletsky, Sergey A.; Piletska, Elena V.; Bossi, Alessandra; Karim, K.; Lowe, P.; Turner, Anthony P. F.A new technique for coating microtitre plates with molecularly imprinted polymers (MIP), specific for low-molecular weight analytes (epinephrine, atrazine) and proteins is presented. Oxidative polymerization was performed in the presence of template; monomers: 3-aminophenylboronic acid, 3- thiopheneboronic acid and aniline were polymerized in water and the polymers were grafted onto the polystyrene surface of the microplates. It was found that this process results in the creation of synthetic materials with antibody-like binding properties. It was shown that the MIP-coated microplates are particularly useful for assay development. The high stability of the polymers and good reproducibility of the measurements make MIP coating an attractive alternative to conventional antibodies or receptors used in ELISA.Item Open Access Too large to fit? Recent developments in macromolecular imprinting.(Elsevier Science B.V., Amsterdam., 2008-04-01T00:00:00Z) Ge, Yi; Turner, Anthony P. F.Molecular imprinting involves the synthesis of polymers in the presence of a template to produce complementary binding sites with specific recognition ability. The technique has been successfully applied as a measurement and separation technology, producing a uniquely robust and antibody-like polymeric material. Low molecular weight molecules have been extensively exploited as imprint templates, leading to significant achievements in solid-phase extraction, sensing and enzyme-like catalysis. By contrast, macromolecular imprinting remains underdeveloped, principally because of the lack of binding site accessibility. In this review, we focus on the most recent developments in this area, not only covering the widespread use of biological macro-templates but also highlighting the emerging use of synthetic macro-templates, such as dendrimers and hyperbranched polymers.Item Open Access Using a linked soil model emulator and unsaturated zone leaching model to account for preferential flow when assessing the spatially distributed risk of pesticide leaching to groundwater in England and Wales(Elsevier Science B.V., Amsterdam., 2004-01-05T00:00:00Z) Holman, Ian P.; Dubus, Igor G.; Hollis, J. M.; Brown, Colin D.Although macropore flow is recognized as an important process for the transport of pesticides through a wide range of soils, none of the existing spatially distributed methods for assessing the risk of pesticide leaching to groundwater account for this phenomenon. The present paper presents a spatially distributed modelling system for predicting pesticide losses to groundwater through micro- and macropore flow paths. The system combines a meta version of the mechanistic, dual porosity, preferential flow pesticide leaching model MACRO (the MACRO emulator), which describes pesticide transport and attenuation in the soil zone, to an attenuation factor leaching model for the unsaturated zone. The development of the emulator was based on the results of over 4000 MACRO model simulations. Model runs describe pesticide leaching for the range of soil types, climate regimes, pesticide properties and application patterns in England and Wales. Linking the MACRO emulator to existing spatial databases of soil, climate and compound-specific loads allowed the prediction of the concentration of pesticide leaching from the base of the soil profile (at 1 m depth) for a wide range of pesticides. Attenuation and retardation of the pesticide during transit through the unsaturated zone to the watertable was simulated using the substrate attenuation factor model AQUAT. The MACRO emulator simulated pesticide loss in 10 of 12 lysimeter soil-pesticide combinations for which pesticide leaching was shown to occur and also successfully predicted no loss from 3 soil-pesticide combinations. Although the qualitative aspect of leaching was satisfactorily predicted, actual pesticide concentrations in leachate were relatively poorly predicted. At the national scale, the linked MACRO emulator / AQUAT system was found to predict the relative order of, and realistic regional patterns of, pesticide leaching for atrazine, isoproturon, chlorotoluron and lindane. The methodology provides a first-step assessment of the potential for pesticide leaching to groundwater in England and Wales. Further research is required to improve the modelling concept proposed. The system can be used to refine regional groundwater monitoring system designs and sampling strategies and improve the cost-effectiveness of the measures needed to achieve “good status” of groundwater quality as required by the Water Framework DirectItem Open Access What can scenario modelling tell us about future European scale agricultural land use, and what not?(Elsevier Science B.V., Amsterdam., 2006-04-01T00:00:00Z) Audsley, Eric; Pearn, Kerry R.; Simota, C.; Cojocaru, G.; Koutsidou, E.; Rounsevell, M. D. A.; Trnka, M.; Alexandrov, V.Given scenarios describing future climates and socio-techno-economics, this study estimates the consequences for agricultural land use, combining models of crop growth and farm decision making to predict profitability over the whole of Europe, driven solely by soil and climate at each location. Each location is then classified by its profitability as intensive or extensive agriculture or not suitable for agriculture. The main effects of both climate and socio- economics were in the agriculturally marginal areas of Europe. The results showed the effect of different climates is relatively small, whereas there are large variations when economic scenarios are included. Only Finland's agricultural area significantly responds to climate by increasing at the expense of forests in several scenarios. Several locations show more difference due to climate model (PCM versus HadCM3) than emission scenario, because of large differences in predicted precipitation, notably the Ardennes switching to arable in HadCM3. Scenario modelling has identified several such regions where there is a need to be watchful, but few where all of the scenario results agree, suggesting great uncertainty in future projections. Thus, it has not been possible to predict any futures, though all results agree that in Central Europe, changes are likely to be relatively small.