No description available.

No description available.

No description available.

A range of mesoporous materials based on SBA-15, KIT-6 and FDU-12 have been prepared using neutral block copolymers Pluronic P123 and F127 and characterised using methods including electron microscopy and nitrogen adsorption. Typically the materials have a hexagonal (p6mm) or cubic (Fm3m and Ia-3d) symmetry and pore geometry and are rendered porous by either calcination or solvent extraction. Organic functional groups were incorporated into the silica walls of the materials by co-condensation in the form of propyl thiols and additives in the form of alkanes were added to control pore size and geometry. The effects of temperature, additives, organic functionalisation, synthesis time and sol-gel composition were investigated and the resulting materials were tested as supports for protein adsorption, enzyme immobilisation, and drug delivery. Two FDU-12 materials of differing entrance and cavity sizes were used to adsorb a range of proteins with molecular weight 17 to 160 kDa to determine if there was a size exclusion effect. It was seen that the larger pore material was able to adsorb proteins of a larger size (molecular weight 105 kDa) and an exclusion effect was observed when the dimension of the proteins became too great (larger than 130 kDa). There was no clear trend for the smaller pore material where each protein was adsorbed to some extent by the material but apart from the smallest protein, myoglobin, mainly on the surface and not within the pores. The adsorption of the lipase B from Candida Antartica, CALB, was studied on a range of mesoporous supports with their templates removed by either calcination or extraction. The effect of pore size and functionalisation was investigated in terms of maximum loading and rate of loading. By functionalising the KIT-6 material the maximum loading of CALB was reduced from 45.5 to 32 mg/g whereas functionalising the FDU-12 material increased the maximum from 33 to 42.5 mg/g. The activity of the immobilised CALB was measured by enantioselective transesterification of (R)-1-phenylethanol in methyltetrabutyl ether (MTBE). The effect of loading, surface functionalisation and reusability in organic media were investigated. Functionalisation with propyl thiol was seen to increase the rate of conversion after 30 minutes for both KIT-6 and FDU-12 materials. Selected FDU-12 and KIT-6 materials with window sizes from 6 to 12 nm and with and without functionalisation were used to carry out a drug release study using Bovine serum albumin (BSA). BSA was loaded onto the material and the uptake quantified using nitrogen adsorption, elemental analysis, and thermogravimetric analysis. The release of BSA into simulated body fluid at 37 ºC was measured using HPLC. Functionalisation was seen to have little effect. The type of cubic morphology controlled the rate at which the BSA was released. The KIT-6 3D channel material exhibited a burst release initially followed by a steady release of BSA whereas the mesocage FDU-12 material had a slower and more linear release profile, closer to that desired.

Ce manuscrit de thèse présente le développement de méthodes basées sur la spectrométrie de masse consacrées à la recherche d'inhibiteurs d'enzymes en milieux complexes, tels que les extraits de plantes. L’enzyme Tyrosinase a été utilisé comme principale cible biologique du fait de son implication dans les processus d’hyperpigmentation cutanée. De ce fait, la recherche d’inhibiteurs de cette enzyme, présente un grand intérêt pour l'industrie cosmétique. La première partie de ce manuscrit décrit la mise en place de la chromatographie d'affinité frontale (FAC), permettant d’obtenir le classement simultané des inhibiteurs présent dans un mélange complexe en fonction de leurs affinités avec la cible biologique. Deux capillaires hydrophiles de phase monolithiques ont été évalués afin de réduire au maximum les interactions non spécifiques indésirables entre les analytes et le support solide d’immobilisation. De plus, nous avons étudié la faisabilité de l’utilisation de phases à base de silice comme support solide d’immobilisation des enzymes dans le cadre de ces analyses par chromatographie d'affinité frontale. La seconde partie du manuscrit de thèse est consacrée au développement et à l’optimisation de l’approche nommée ENALDI-MS (Enzyme-coupled Nanoparticles-Assisted Laser Desorption/Ionisation Mass Spectrometry) permettant d’accéder à une gamme des faibles masses (m/z 500 Da). Elle est déclinée en une première approche dite par ‘extinction d’ions’ (Ion Fading, IF-ENALDI), basée sur l’identification directe de la liaison des inhibiteurs vis-à-vis de l’enzyme sans pré-traitement de l’échantillon végétal. Une seconde déclinaison de l’ENALDI-MS concerne une approche dite par ‘Ion Hunting’ (IH - ENALDI MS), basée sur une méthode de pré-concentration sélective des inhibiteurs présents dans l'échantillon. / This thesis report presents the development of mass spectrometry-based methods for searching for inhibitors of enzymes in complex mixtures, such as plant extracts. Tyrosinase enzyme was used as the main biological target for the reason of a significant importance of its inhibitors in the cosmetic industry as the skin whitening agents. The first part of this report describes Frontal Affinity Chromatography (FAC), an approach enabling simultaneous ranking the inhibitors within the complex mixture according to their affinities to the biological target. Two hydrophilic capillary-scale polymer-based bioaffinity stationary phases were evaluated in the context of the presence of undesirable nonspecific interactions between the analyte and the solid immobilisation support. In addition, we explored the usability of two types of silica-based particles as a solid support for enzyme immobilisation for FAC. The second part of the thesis manuscript is devoted to Enzyme-coupled Nanoparticle-Assisted Laser Desorption/Ionisation Mass Spectrometry (ENALDI MS) as a low-mass compatible extension of the Intensity ion Fading MALDI MS (IF-MALDI MS) method for high-throughput screening of the inhibitors in the complex mixtures. Two variations of ENALDI MS were evaluated: 'Ion Fading' (IF-ENALDI MS), based on on-the-spot binding of inhibitors by enzyme molecules and 'Ion Hunting' (IH-ENALDI MS), based on selective pre-concentration of inhibitors present in the sample.