Staff publications - Cranfield Health

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Open Access
Potential for detection of microorganisms and heavy metals in potable water using electronic nose technology.
(Elsevier, 2003-05) Canhoto, Olinda; Magan, Naresh
Studies have been carried out to determine the potential for the detection of different microbial species (Enterobacter aerogenes, Escherichia coli, Pseudomonas aeruginosa), alone and in the presence of low concentrations of different heavy metals (As, Cd, Pb and Zn) in bottled, reverse osmosis (RO) and tap water, using an electronic nose. Studies show that it is possible to discriminate control water samples from water contaminated with 0.5 ppm of a mixture of metals. The presence of heavy metals may modify the activity of microorganisms and thus the volatile production patterns. Bacterial species at 102–104 colony forming units (CFUs) ml−1 could be detected after 24 h of incubation. Work is in progress to identify the limits of detection for a range of other microorganisms, including, fungi and cyanobacteria, and chlorinated phenols using electronic nose technology.
Open Access
Water activity, solute and temperature modify growth and spore production of wild type and genetically engineered Aspergillus niger strains.
(Elsevier, 2004-08-05) Parra, Roberto; Aldred, David; Archer, David B.; Magan, Naresh
The effect of interactions of water activity (aw) (0.99–0.90), temperature (20, 30 and 35 °C) and modifying aw solute (glycerol, NaCl) on growth and sporulation of a wild-type strain of Aspergillus niger (W) and two genetically engineered lysozyme-producing strains (L11, B1) was examined for the first time. Maximum growth rates were achieved for both strains (L11 and B1) under moderate aW levels. L11 showed a higher growth rate than B1. Fastest growth was achieved at 30 °C, using glycerol as solute. Optimum conditions for growth of strain L11 were estimated by means of contour plot surfaces and found to be 0.965 aw with glycerol as solute at 35 °C. The predicted value of the optimum growth rate was 10.5 mm/day. A value of 10.85 mm/day was obtained experimentally giving a good correlation between the estimated and the measured results. Sporulation was optimum for the W strain at 0.99–0.95 by B1 at 35 °C. Significant higher production of conidia by L11 at 0.97–0.93 aw and at 0.97 aw and 35 °C for B1 strain was observed. Optimum conditions for spore production were different from those for growth. Under similar ecological conditions, the W and both the genetically engineered strains had a different growth and sporulation pattern.
Open Access
Photochemical polymerization of thiophene derivatives in aqueous solution
(Royal Society of Chemistry, 2004-08-20T00:00:00Z) Piletsky, Sergey A.; Piletska, Elena V.; Karim, K.; Davis, Frank; Higson, Seamus P. J.; Turner, Anthony P. F.
A novel method of photochemical polymerization of thiophene derivatives in aqueous solution catalyzed by potassium dichromate and initiated by illumination is described.
Open Access
Surface plasmon resonance sensor for domoic acid based on grafted imprinted polymer
(Elsevier Science B.V., Amsterdam., 2004-09-15T00:00:00Z) Lotierzo, M.; Henry, O. Y. F.; Piletsky, Sergey A.; Tothill, Ibtisam E.; Cullen, David C.; Kania, M.; Hock, B.; Turner, Anthony P. F.
A molecularly imprinted polymer (MIP) film for domoic acid (DA) was synthesised by direct photo-grafting onto a gold chip suitable for a surface plasmon resonance (SPR) based bioanalytical instrument system, the BIAcore 3000™. The gold surface was first functionalised with a self-assembled monolayer of 2- mercaptoethylamine and subsequent carbodiimide chemistry was performed for covalent attachment of the photoinitiator, 4,4′-azobis(cyanovaleric acid). This ensured that the formation of the MIP thin film, comprising 2-(diethylamino) ethyl methacrylate as functional monomer and ethylene glycol dimethacrylate as cross-linker, occurred only at the surface level. Optimisation and control over the grafting procedure were achieved using contact angle measurements and atomic force microscope (AFM) imaging. The surface grafting resulted in the formation of thin and homogeneous MIP film with thickness of 40 nm. A competitive binding assay was performed with free DA and its conjugate with horseradish peroxidase, which was used as a refractive label. The sensor was evaluated for its sensitivity, cross-reactivity, and robustness by using a BIAcore 3000™. Likewise, monoclonal antibodies acting as natural receptors for the toxin were studied with the same BIAcore system. Results of a comparison between the artificial and natural receptors are reported. In contrast to monoclonal antibodies, the regeneration of MIP chip did not affect its recognition properties and continuous measurement was possible over a period of at least 2 m
Open Access
Evaluation of an FIA Operated Amperometric Bacterial Biosensor, Based on Pseudomonas Putida F1 for the Detection of Benzene, Toluene, Ethylbenzene, and Xylenes (BTEX)
(Taylor and Francis, 2005) Rasinger, Josef D.; Marrazza, Giovanna; Briganti, Fabrizio; Scozzafava, Andrea; Mascini, Marco; Turner, Anthony P. F.
Recently, the development and optimization of a flow injection analysis (FIA) operated bacterial biosensor based on the aerobic catabolism of Pseudomonas putida ML2 was reported in the literature (Lanyon et al. 2004, 2005). By adapting information from these reports, we investigated whether operating parameters and procedures of the benzene biosensor could be directly applied to a new system based on a different bacterial strain for the detection of the whole benzene, toluene, ethylbenzene, and xylenes range. Cells of the investigated bacterial strain, Pseudomonas putida F1, were immobilized between two cellulose acetate membranes and fixed onto a Clark dissolved oxygen electrode. The P. putida F1 aerobically degrades benzene, toluene, and ethylbenzene (BTE) (Cho et al. 2000). The BTE biosensor in kinetic mode FIA displayed a linear range of 0.02-0.14 mM benzene (response time: 5 min, base-line recovery time: 15 min), 0.05-0.2 mM toluene (response time: 8 min, baseline recovery time: 20 min), and 0.1-0.2 mM ethylbenzene (response time: 12 min, baseline recovery time: 30 min), respectively. Due to the differences in sensitivity, response, and baseline recovery times for BTE, it was possible to differentiate each compound in mixtures of these volatile organic compounds (VOCs). No response for xylenes could be obtained since they cannot be completely metabolized by this bacterial strain. However, it was reported that the range of compounds degradable by P. putida F1 can possibly be expanded by cultivating the cells on different carbon sources (Choi et al. 2003). The sensor showed good intra- and interassay reproducibility, and all obtained results were comparable with those reported in the literature. The demonstrated reproducibility and the simplicity and ease of use as well as the portability for in situ measurements indicates that the biosensor could be suitable as a reliable initial warning device for elevated BTE levels in indoor and outdoor environments.
Open Access
Species differentiation by DNA-modified carbon electrodes using an ac impedimetric approach.
(Elsevier Science B.V., Amsterdam., 2005-02-15T00:00:00Z) Davis, Frank; Nabok, Alexei; Higson, Seamus P. J.
A simple and novel electrochemical biosensor based approach is described for differentiating between differing species of fish on the basis of DNA hybridisation events. Screen-printed carbon electrodes modified with a variety of polymers were used to immobilise commercially available DNA in a single- stranded form. AC impedimetric measurements were firstly carried out on these systems and then upon exposure to single-stranded DNA solutions. When the electrode and solution DNA were complementary, a large drop in impedance was measured; this did not occur for non-matching DNA exposures. DNA hybridisation sensors for closely related species of fish were in the first instance developed as a demonstration for this approach. Species of fish such as herrings and salmon could be differentiated by this method. This sensor format offers great promise for many DNA hybridisation applications and lends itself to mass fabrication due to the simplicity and inexpensiveness of the materials and methods used. The hybridisation results were confirmed by use of ellipsometry to measure the characteristics of similar films deposited on silicon substrates.
Open Access
A novel optical biosensor format for the detection of clinically relevant TP53 mutations
(Elsevier, 2005-05-15) Wilson, P. K.; Jiang, T.; Minunni, Maria E.; Turner, Anthony P. F.; Mascini, Marco
The TP53 gene has been the subject of intense research since the realisation that inactivation of this gene is common to most cancer types. Numerous publications have linked TP53 mutations in general or at specific locations to patient prognosis and therapy response. The findings of many studies using general approaches such as immunohistochemistry or sequencing are contradictory. However, the detection of specific mutations, especially those occurring in the structurally important L2 and L3 zinc binding domains, which are the most common sites of TP53 mutations, have been linked to patient prognosis and more strongly to radiotherapy and chemotherapy resistance in several major cancers. In this study, the TI-SPR-1 surface plasmon resonance system and Texas Instruments Spreeta™ chips were used to develop a DNA biosensor based on thiolated probes complementary to these domains. The sensors were able to detect these mutations in both oligonucleotides and PCR products with normal and mutant TP53 DNA, but the difference in hybridisation signal was small. Preliminary experiments to enhance the signal using Escherichia coli mismatch repair proteins, MutS and single strand binding protein were carried out. It was found that MutS was unable to bind to mismatch oligonucleotides, but single strand binding protein was able to bind to single stranded probes, which had not hybridised to the target, resulting in a three-fold increase in the sensitivity of the biosensor. While further work needs to be carried out to optimise the system, these preliminary experiments indicate that the TI-SPR-1 can be used for the detection of clinically relevant mutations in the TP53 gene and that the sensitivity can be increased significantly using single strand binding protein. This system has a number of advantages over current mutation detection technologies, including lower cost, ease of sensor preparation and measurement procedures, technical simplicity and increased speed due to the lack of need for gel electrophoresis.
Open Access
Home blood glucose biosensors: a commercial perspective
(Elsevier, 2005-06-15) Newman, Jeffrey D.; Turner, Anthony P. F.
Twenty years on from a review in the first issue of this journal, this contribution revisits glucose sensing for diabetes with an emphasis on commercial developments in the home blood glucose testing market. Following a brief introduction to the needs of people with diabetes, the review considers defining technologies that have enabled the introduction of commercial products and then reviews the products themselves. Drawing heavily on the performance of actual instruments and publicly available information from the companies themselves, this work is designed to complement more conventional reviews based on papers published in scholarly journals. It focuses on the commercial reality today and the products that we are likely to see in the near future.
Open Access
Towards the development of multisensor for drugs of abuse based on molecular imprinted polymers.
(Elsevier Science B.V., Amsterdam., 2005-06-22T00:00:00Z) Piletska, Elena V.; Romero-Guerra, M.; Chianella, Iva; Karim, K.; Turner, Anthony P. F.; Piletsky, Sergey A.
The synthetic receptors for cocaine, deoxyephedrine, methadone and morphine were computationally designed and produced using molecular imprinting. The structure and energy of the molecular complexes were analysed by computational techniques. The possible structures of the binding sites in the synthetic receptors have been compared with those of corresponding natural receptors. The composition of imprinted polymers was optimised to allow adequate performance under the same experimental conditions. All selected molecular imprinting polymers (MIPs) demonstrated stronger affinity in comparison with corresponding blank polymers resulting in imprinted factors (I) equal to 1.2 (cocaine), 2.5 (deoxyephedrine), 3.5 (methadone) and 3 (morphine) which suggested that the specific binding site for each molecule was successfully created. The polymers studied possessed good selectivity and affinity towards their templates and could be recommended for the integration with sensor devices. From a practical point of view, especially for multisensor requirements, the synthetic receptors based on imprinted polymers could be superior to natural receptors due to their stability, robustness and compatibility with automation processes required for sensor fabrication.
Open Access
Controlled release of the herbicide simazine from computationally designed molecularly imprinted polymers
(Elsevier Science B.V., Amsterdam., 2005-11-02T00:00:00Z) Piletska, Elena V.; Turner, Nicholas W.; Turner, Anthony P. F.; Piletsky, Sergey A.
The present study describes the development of materials suitable for environmental control of algae. Molecularly imprinted polymers (MIPs) were used as simazine carriers able to provide the controlled release of simazine into water. Three polymers were designed using computational modelling. The selection of methacrylic acid (MA) and hydroxyethyl methacrylate (HEM) as functional monomers was based on results obtained using the Leapfrog™ algorithm. A cross- linked polymer made without functional monomers was also prepared and tested as a control. The release of simazine from all three polymers was studied. It was shown that the presence of functional monomers is important for polymer affinity and for controlled release of herbicide. The speed of release of herbicide correlated with the calculated binding characteristics. The high-affinity MA- based polymer released 2% and the low-affinity HEM-based polymer released 27% of the template over 25 days. The kinetics of simazine release from HEM-based polymer show that total saturation of an aqueous environment could be achieved over a period of 3 weeks and this corresponds to the maximal simazine solubility in water. The possible use of these types of polymers in the field of controlled release is discusse
Open Access
The Objective Structured Clinical Examination and student collusion: marks do not tell the whole truth.
(BMJ Publishing Group, 2006-01-01T00:00:00Z) Parks, R.; Warren, P. M.; Boyd, K. M.; Cameron, H.; Cumming, A.; Lloyd-Jones, G.
Objective: To determine whether the marks in the third year Objective Structured Clinical Examination (OSCE) were affected by the collusion reported by the students themselves on an electronic discussion board.reported by the students themselves on an electronic discussion board.
Open Access
Development of a disposable pyruvate biosensor to determine pungency in onions (Allium cepa L.)
(Elsevier, 2006-05-15) Abayomi, Louise Anike; Terry, Leon A; White, S. F.; Warner, P. J.
A disposable prototype pyruvate biosensor was constructed using pyruvate oxidase immobilised on mediated meldolas blue electrodes to determine pungency in onions (Allium cepa L.). The optimum operating potential was +150 mV (versus Ag/AgCl). A strong correlation between the biosensor response and untreated onion juice of known pyruvate concentration 2–12 μmol/g fresh weight (FW) was demonstrated. The biosensor was able to differentiate between low and high pungency onions. The detection limit using 1 unit of pyruvate oxidase was 1–2 μmol/g FW. Optimum concentrations of co-factors TPP, FAD and MgSO4 comprising the enzyme cocktail were determined as being 0.04, 0.1 and 30 mM, respectively.
Open Access
Influence of initiator and different polymerisation conditions on performance of molecularly imprinted polymers
(Elsevier Science B.V., Amsterdam., 2006-09-15T00:00:00Z) Mijangos, Irene; Navarro-Villoslada, Fernando; Guerreiro, Antonio R.; Piletska, Elena V.; Chianella, Iva; Karim, Kal; Turner, Anthony P. F.; Piletsky, Sergey A.
A set of polymers was imprinted with (−)-ephedrine using two different initiators. A chemometrics approach was used to optimise experiments aimed at analysis of the interplay of parameters such as polymerisation time, temperature and percentage of initiator. The results presented demonstrate the importance of keeping the right balance between these various parameters of polymerisation conditions. It is shown that enhancing one single parameter such as polymer rigidity does not necessarily improve polymer performance. In general it could be concluded that MIPs should be synthesised over a long period of time using low concentration of initiator and low temperature. The best selectivity was achieved for polymers prepared by photo-initiation with 2,2-dimethoxy-2-phenylacetophenone as initiatotor
Open Access
Trichophyton species: use of volatile fingerprints for rapid identification and discrimination.
(Blackwell Publishing, 2006-12) Sahgal, Natasha; Monk, Barry; Wasil, Mohammad; Magan, Naresh
Background: Fungal infection of the skin is a common clinical problem, and laboratory confirmation of the diagnosis is important to ensure appropriate treatment. The identification of the species of fungus is also important, because different fungal species have different modes of transmission, and this may be of importance both in preventing re-infection or in avoidance of infection of others. Objective: This study examined the potential of using volatile production patterns for the detection and discrimination between four Trichophyton species (T. mentagrophytes, T. rubrum, T. verrucosum and T. violaceum) in vitro on solid media and in broth culture. Methods: Two different sensor array systems (conducting polymer and metal oxide sensors) were examined for comparing the qualitative volatile fingerprints produced by these species over periods of 24-120 hrs in the headspace. The relative sensitivity of detection of two of the species (T. mentagrophytes, T. rubrum) was determined for log1 to log7 inoculum levels over the same time period. Results: The conducting polymer based system was unable to differentiate between species based on volatile fingerprints over the experimental period. However, metal oxide-based sensor arrays were found to be able to differentiate between the four species within 96 hrs of growth using PCA analysis which accounted for approximately 93% of the data in PC1 and 2 based on the qualitative volatile production patterns. This differentiation was confirmed by the Cluster analysis of the data using Euclidean distance and Ward’s linkage. Studies of the sensitivity of detection showed that for T. mentagrophytes and T. rubrum it was possible to differentiate between log3, log5 and log7 inoculum levels within 96 hrs. Conclusions: This is the first detailed study of the use of qualitative volatile fingerprints for identification and discrimination of dermatophytes. This approach could have potential for rapid identification of patient samples reducing significantly the time to treatment.
Open Access
Labeless Immunosensor Assay for Fluoroquinolone Antibiotics Based Upon an AC Impedance Protocol.
(Taylor & Francis, 2007-01-01T00:00:00Z) Garifallou, Goulielmos-Zois; Tsekenis, Georgios; Davis, Frank; Higson, Seamus P. J.; Millner, Paul A.; Pinacho, Daniel G.; Sanchez-Baeza, Francisco; Marco, M-Pilar; Gibson, Timothy D.
This paper describes the construction of a labeless immunosensor for the antibiotic ciprofloxacin and its interrogation using an AC impedance protocol. Commercial screen-printed carbon electrodes were used as the basis for the sensor. Polyaniline was electrodeposited onto the sensors and then utilized to immobilize a biotinylated antibody for ciprofloxacin using classical avidin- biotin interactions. Electrodes containing the antibodies were exposed to solutions of antigen and interrogated using an AC impedance protocol. The faradaic component of the impedance of the electrodes was found to increase with increasing concentration of antigen. Control samples containing a non-specific IgG antibody were also studied and calibration curves obtained by subtraction of the responses for specific and non-specific antibody-based sensors, thereby eliminating the effects of non-specific adsorption of antigen.
Open Access
Flexible Ultrathin PolyDVB/EVB Composite Membranes for the Optimization of a Lactate Sensor.
(John Wiley & Sons, Ltd, 2007-01-01T00:00:00Z) Bridge, Kerry; Davis, Frank; Collyer, Stuart D.; Higson, Seamus P. J.
An ultrathin composite membrane has been developed as the outer covering barrier in a model amperometric lactate oxidase enzyme electrode. The membrane was formed by cathodic electropolymerization of divinylbenzene/ethylvinylbenzene at the surface of a gold coated polyester support membrane. Permeability coefficients were determined for O2 and lactate across membranes with a range of polymer thicknesses. Anionic interferents (such as ascorbate) were screened from the working electrode by the composite membrane. The composite enzyme electrode showed an increased working concentration range and extended linearity of responses in comparison to an uncoated enzyme electrode.
Open Access
Procedure 24 : Construction of an enzyme-containing microelectrode array and use for detection of low levels of pesticides
(2007-01-01T00:00:00Z) Davis, Frank; Law, Karen A.; Turner, Anthony P. F.; Higson, Seamus P. J.
Objectives (a) To construct a microelectrode array based on a screen printed substrate. (b) To utilise the microelectrode array to form an array of enzyme- containing electrodes (c) To test the electrode response to thiocholine (d) To expose the array to low levels of pesticide and measure the relative response to thiocholine following inhibition.
Open Access
Flexible Ultrathin PolyDVB/EVB Composite Membranes for the Optimization of a Whole Blood Glucose Sensor.
(John Wiley & Sons, Ltd, 2007-01-01T00:00:00Z) Bridge, Kerry; Davis, Frank; Collyer, Stuart D.; Higson, Seamus P. J.
An ultrathin composite membrane has been developed as the outer covering barrier in a model amperometric glucose oxidase enzyme electrode. The membrane was formed by cathodic electropolymerization of divinylbenzene/ethylvinylbenzene at the surface of a gold coated polyester support membrane. Permeability coefficients were determined for O2 and glucose across membranes with a range of polymer thicknesses. Anionic interferents (such as ascorbate), were screened from the working electrode via a charge exclusion mechanism. The enzyme electrode showed an initial 10% signal drift when first exposed to whole human blood over a period of 2 hours, after which responses remained essentially stable. Whole blood patient glucose determinations yielded a correlation coefficient of r2=0.99 compared to standard hospital analyses.
Open Access
Biofuelcells-Recent advances and applications
(Elsevier, 2007-02-15) Davis, Frank; Higson, Seamus P. J.
In 2006, the journal Biosensors and Bioelectronics published a special issue devoted exclusively to biofuel cells, including several research papers and an extensive review of the field [Bullen, R.A., Arnot, T.C., Lakeman, J.B., Walsh, F.C., 2006. Biosens. Bioelectron.]. Within this review a brief description will firstly be given of the history of biofuel cells together with coverage of some of the major historical advances. The review is intended, however, to largely concentrate on and give an overview of the advances made in recent years in this area together with a discussion surrounding the practical application of biofuel cells. There are several classes of biofuel cells: we shall firstly discuss the recent advances in biofuel cells that convert chemical fuels to produce electrical power by use of catalytic enzymes. This will be followed by a section on similar cells where micro-organisms rather than enzymes are used to convert the fuel to energy. Thirdly we shall consider hybrid biofuel cells that combine the utilisation of photochemical chemistries and biological systems for the generation of electricity. Finally we will discuss some of the proposed uses of biofuel cells together with a short consideration of future research possibilities and applications of these systems.
Open Access
Surface imprinted beads for the recognition of human serum albumin
(Elsevier Science B.V., Amsterdam., 2007-04-15T00:00:00Z) Bonini, Francesca; Piletsky, Sergey A.; Turner, Anthony P. F.; Speghini, Adolfo; Bossi, Alessandra
The synthesis of poly-aminophenylboronic acid (ABPA) imprinted beads for the recognition of the protein human serum albumin (HSA) is reported. In order to create homogeneous recognition sites, covalent immobilisation of the template HSA was exploited. The resulting imprinted beads were selective for HSA. The indirect imprinting factor (IF) calculated from supernatant was 1.6 and the direct IF, evaluated from the protein recovered from the beads, was 1.9. The binding capacity was 1.4 mg/g, which is comparable to commercially available affinity materials. The specificity of the HSA recognition was evaluated with competitive experiments, indicating a molar ratio 4.5/1 of competitor was necessary to displace half of the bound HSA. The recognition and binding of the imprinted beads was also tested with a complex sample, human serum and targeted removal of HSA without a loss of the other protein components was demonstrated. The easy preparation protocol of derivatised beads and a good protein recognition properties make the approach an attractive solution to analytical and bio-analytical problems in the field of biotechnology.