Journal articles

The use of an acoustic wave device as a chemical sensing element is often limited by contact with wires and supports and by the need to control its fluidic environment. This letter describes the validation of a versatile noncontact configuration that makes use of a spiral coil antenna to electromagnetically excite miniature piezoelectric chips. Experimental evidence is provided to demonstrate that an AT cut quartz crystal resonator can be cleaved into chips that can be excited electromagnetically via coupling to the electric Y axis of the crystal.

In this study, 2-acrylamido-phenylboronate (2-APB) was synthesised and its ability to bind with glucose was investigated both in solution and when integrated into a holographic sensor. Multiple forms of 2-APB, resulting from the neighbouring effect of the amido group with the boronic acid through an intramolecular B-O-coordinated interaction, were shown to exist in solution by using multinuclear NMR spectrometry. It was found that 2-APB predominantly adopts a zwitterionic tetrahedral form at physiological pH values.

Prion diseases, or transmissible spongiform encephalopathies (TSEs) are typically characterised by CNS accumulation of PrPSc, an aberrant conformer of a normal cellular protein PrPC. It is thought PrPSc is itself infectious and the causative agent of such diseases. To date, no chemical modifications of PrPSc, or a sub-population thereof, have been reported. In this study we have investigated whether chemical modification of amino acids within PrP might cause this protein to exhibit aberrant properties and whether these properties can be propagated onto unmodified prion protein.

Holographic sensors for the detection of Bacillus species spore germination and vegetative growth are described. Reflection holograms were fabricated using a diffusion method for the distribution of ultra-fine silver bromide grains into pre-formed polymer films, followed by holographic recording using a frequency doubled Nd:YAG (532 nm) laser.

A technique is described for the entrapment of glucose oxidase in a polypyrrole matrix electrochemically deposited on a printed platinum electrode. The enzyme activity incorporated into the polymer was quantified by spectrophotometric assay using a flow-through cell and found to be proportional to the activity in the electropolymerisation medium. Polymer-entrapped glucose oxidase electrodes can be operated as amperometric glucose sensors in the presence or absence of soluble mediators.

Glucose oxidase (GOx) has been chemically derlvatlzed by coupling N-( 2-carboxyethyl )pyrrole to surface lysyl residues with a carbodmmide-promoted reaction. The modified enzyme (30.2 ± 0.5 mol of pyrrole/mol of GOx) displayed almost Identical properties to the native enzyme except that the pi was slightly more acidic and the stability was 6-fold higher at pH 7.0 and 60 °C. The protein-substituted pyrroles were accessible to electrochemical oxidation and In the presence of free pyrrole generated copolymers which covalently Incorporated GOx.

Glucose oxidase (GOx) was modified chemically with 3-carboxymethyl pyrrole by a carbodiimide coupling reaction. A maximum of 20 pyrrole moieties was attached to lysyl residues of the enzyme. They were shown to be electro-oxidizable. Copolymerization of the pyrrole-modified enzyme with pyrrole monomers resulted in polymer films exhibiting higher immobilized enzyme activity compared with previously studied copolymerized enzyme films using N-derivatized pyrrole.

The formation of supported lipid mono- and bilayers on a thiol-coated surface was monitored by utilising the acoustic Love waveguide device. The detection of the lipid layers was used as a model system for relating the phase response to the deposited mass and studying the sensor's response to the regeneration of the surface. The sensitivity of the acoustic device revealed that, in addition to the mass change occurring during the deposition of the lipid layers, the viscoelastic properties of the interface change significantly.

The interactions of CL4, a biomimetic analogue of NAD+ comprising a nicotinamide functionality coupled via a triazine ring to a dibenzenesulphonic acid unit, and of a series of analogues, with HLADH and other dehydrogenases have been compared to those of the natural coenzymes NAD(P)+. CL4, together with one analogue with one of the sulphonic acid groups shifted by one position and another analogue with a single benzenedisulphonic acid unit, have been shown to be functional mimics of NAD+ in the oxidation of butan-1-ol by horse liver alcohol dehydrogenase (HLADH).

This paper describes the construction of a sensor for the direct monitoring of a recombinant protein, the human insulin analogue (MI3). The surface plasmon resonance (SPR) sensor incorporates an immobilised, sterilisable affinity-ligand that has been designed to bind to MI3.