Thomas G. Nevell

Preventing bacterial adhesion onto surfaces: the low-surface-energy approach.

Good-quality coatings prepared from poly(methylpropenoxyfluoroalkylsiloxane)s or poly(perfluoroacrylate)s are capable of inhibiting the bacterial colonisation of surfaces.

Cospray-dried unfractionated heparin with L-leucine as a dry powder inhaler mucolytic for cystic fibrosis therapy

Accumulation of inspissated secretions that are difficult to clear and congest the airways is a feature of lung disease in patients with cystic fibrosis (CF). These secretions restrict airflow, harbour infection and limit the delivery of inhaled drugs including gene therapy vectors to the underlying target cells. Unfractionated heparin (UFH) has mucolytic properties suggesting that it may be a useful therapeutic agent for lung disease in these patients. For the pulmonary delivery of UFH to patients with CF, the dry powder inhaler has potential advantages over systems using nebulised suspensions. However, spray-dried particles in the appropriate size range (1-5 microm) may absorb atmospheric moisture, causing aggregation. UFH has been cospray-dried with L-leucine (1%, w/w) to produce particles that are less cohesive than UFH alone and show good aerosolisation performance. Rheological analysis has shown that spray-dried UFH and UFH cospray-dried with L-leucine significantly (p < 0.05) reduce the elasticity and yield stress of CF sputum. The superior physical properties of UFH/L-leucine indicate this is the preferred formulation for development as an inhaled mucolytic.

Inhibiting bacterial adhesion onto surfaces : the non-stick coating approach

The use of low-surface-energy poly(methylpropenoxyfluoroalkylsiloxane) or poly(perfluoroacrylate) coatings as a potential means of inhibiting the bacterial colonisation of surfaces, is described and discussed.

Oscillations of methane combustion over alumina-supported palladium catalysts under oxygen-deficient conditions

Abstract The oxidation of methane over Pd/Al 2 O 3 catalysts in flow systems has been investigated at temperatures in the range 250–600°C and with O 2 /CH 4 ratios between 0.5 and 10.0. Oscillatory behaviour in the evolution of heat of reaction was observed for mixtures close to the stoichiometric composition. The frequency of oscillation increased with rising temperature. The amplitude also depended on both temperature and feed gas composition, and was greatest under conditions such that the consumption of oxygen was almost complete. The oscillatory behaviour may be attributed to the periodic or aperiodic changes in a Pd–PdO x active phase, modulated by the specific reaction environment at elevated temperature.

Non-steady activity during methane combustion over Pd/Al2O3 and the influences of Pt and CeO2 additives

Abstract Methane combustion over Pd/Al2O3 catalysts with and without added Pt and CeO2 in both oxygen-rich and methane-rich mixtures at temperatures in the range 250–520°C has been investigated using a temperature-programmed reaction procedure with on-line gas analysis (FTIR). During the temperature loop under oxygen-rich conditions, there was an appreciable hysteresis in the activity of unmodified Pd/Al2O3, which was greatly enhanced over Pd–Pt/Al2O3. Over both catalysts the hysteresis was reversed under slightly methane-rich atmospheres, and as temperature was reduced, a sudden collapse or fluctuations in activity were shown respectively over Pd–Pt/Al2O3 and Pd/Al2O3. Such non-steady behaviour was almost eliminated over Pd/Al2O3–CeO2. Under a very narrow range of conditions and over a Pd/Al2O3 packed bed, oscillation of methane combustion was observed.

Poly(methylpropenoxyfluoroalkylsiloxane)s: a class of fluoropolymers capable of inhibiting bacterial adhesion onto surfaces

Abstract The synthesis and the detailed characterisation of poly(methylpropenoxyfluoroalkylsiloxane)s, a class of materials which are inherently resistant to bacterial colonisation, is described and discussed.

The surface properties of some silicone and fluorosilicone coating materials immersed in seawater

Changes in the surface properties of some silicone elastomers (General Electric RTV11, RTV160 and RTV655) and fluorosilicones (‐(Si(CH3)((CH2)3‐O(CH2)2(CF2)XCF3)‐O)n‐, x = 5,7,9) on prolonged immersion in water (distilled water, artificial seawater, filtered and unfiltered seawater) have been investigated using measurements of advancing and receding contact angles, of surface roughness and of water uptake. Considerable increases in hydrophilicity and surface rugosity are attributed mainly to surface structural rearrangements accompanying absorption of water; these effects are greater for the fluorosilicones and the rugosity of RTV160 also increased considerably. Observations of early marine settlement (up to 16 weeks in flowing seawater), visualised by scanning electron microscopy, showed patchy attachment mainly of bacteria and microalgae while mature biofilms were formed on the poly(methylmethacrylate) controls. Although settlement was least on RTV11 and greatest on the fluorosilicones, the range of variation was small relative to the differences in the long‐term fouling resistance of the materials. The design requirements for fouling resistance of a smooth, soft, uniform surface are supported.

Oxidation state of the surface of palladium in the catalytic combustion of hydrogen

Abstract The activity of supported palladium catalysts for the oxidation of hydrogen (80-500°C, atmospheric pressure) has been investigated using a microcalorimetric technique and X-ray photoelectron spectroscopy. The reaction involved a surface layer of oxygen, and was inhibited by adsorbed water. Palladium (II) oxide was formed on the surface of metallic palladium under oxygen at 450°C. Heating in hydrogen at 250°C reduced this surface layer and produced deactivated catalysts. Activity was subsequently restored by exposure to oxygen at this temperature.

Surface energy characteristics of poly(methylpropenoxyalkylsiloxane) film structures

A series of propenoxyalkanes have been synthesised and grafted onto a poly(methylhydrosiloxane) backbone to give the corresponding polymers. The structure of these polymers and their ability to undergo cross-linking reactions is discussed in the light of spectroscopic analysis. The surface energies of film structures prepared from the same materials are quantified and their ability to resist bacterial attachment is assessed.

Carborane-based derivatives of delocalised lipophilic cations for boron neutron capture therapy: synthesis and preliminary in vitro evaluation

Aimed towards the development and effective delivery of highly boronated antitumour agents for use in the neutron capture therapy of cancer, closo-carboranyl derivatives of Nile blue and salts of dequalinium, rhodamine-123 and tetraphenyl phosphonium incorporating nido-carborane counterions have been synthesized and characterized. A preliminary in vitro evaluation in human cell lines indicated the propensity of these agents to target tumour cells, and to deliver therapeutically relevant quantities of boron.