Peter Carl Anders Alberius

Improved enzymatic activity of Thermomyces lanuginosus lipase immobilized in a hydrophobic particulate mesoporous carrier

Lipase from Thermomyces lanuginosus has been immobilized within particulate mesoporous silica carriers, with either hydrophilic or hydrophobic supporting surfaces, produced by the newly developed emulsion and solvent evaporation (ESE) method. The Michaelis-Menten model was used to calculate the parameters related to the enzymatic activity of lipase i.e. the turnover number, k(cat), and the specific activity. The specific activity was improved by immobilization of lipase onto the hydrophobic support, compared to lipase immobilized onto the hydrophilic support and lipase free in solution. The enhanced enzymatic activity of lipase onto a hydrophobic support was attributed to interfacial activation of the Thermomyces lanuginosus lipase when it is attached to a hydrophobic surface and a reduced denaturation. Confocal scanning laser microscopy (CLSM) studies, of fluorescently tagged lipase, showed that leakage of the lipase from the mesoporous particles was limited to an initial period of only a few hours. Both the rate and the amount of lipase leached were reduced when the lipase was immobilized onto the hydrophobic support.

Coated polystyrene particles as templates for ordered macroporous silica structures with controlled wall thickness

Polystyrene (PS) colloidal particles have been used as templates to produce ordered macroporous silica structures. The silica films were deposited from ethanol solution containing acidic water and tetraethyl orthosilicate. The silica-coated PS spheres were characterized using transmission electron microscopy, and the film thickness determined by scanning electron microscopy and calculated from the relative weight of silica remaining after calcination. We found that the thickness of the silica film increased rapidly with time and reached a maximum that varied from 40 to 15 nm at pH 1.5 and 3, respectively. The data could be fitted to a simple first-order equation and the reaction rate and maximum thickness were related to the hydrolysis and condensation rate, respectively. Ordered macroporous structures were formed by centrifuging silica-coated PS spheres. Calcination of the close-packed spheres yielded a continuous silica matrix consisting of a three-dimensional well-ordered network of monodisperse pores.

One-pot synthesis of well ordered mesoporous magnetic carriers

The facile preparation of a mesoporous magnetic carrier technology is demonstrated. The micron-sized spherical mesostructured particles are prepared using a newly-developed, one-step, combined emulsion and solvent evaporation (ESE) method. The surfactant-templated silica matrix display a well-ordered internal pore architecture. Very limited pore blocking, and only to a limited degree disordered- or worm-like structures are observed, induced by the iron oxide nanoparticles added to provide the superparamagnetic properties.The iron oxide content was precisely controlled, and the magnetic properties were well preserved during the process. Finally we demonstrate the applicability of the magnetically separable mesoporous material as an adsorbent for specific dissolved materials from dilute aqueous solutions.

AFM-porosimetry: density and pore volume measurements of particulate materials.

We introduced the novel technique of AFM-porosimetry and applied it to measure the total pore volume of porous particles with a spherical geometry. The methodology is based on using an atomic force microscope as a balance to measure masses of individual particles. Several particles within the same batch were measured, and by plotting particle mass versus particle volume, the bulk density of the sample can be extracted from the slope of the linear fit. The pore volume is then calculated from the densities of the bulk and matrix materials, respectively. In contrast to nitrogen sorption and mercury porosimetry, this method is capable of measuring the total pore volume regardless of pore size distribution and pore connectivity. In this study, three porous samples were investigated by AFM-porosimetry: one ordered mesoporous sample and two disordered foam structures. All samples were based on a matrix of amorphous silica templated by a block copolymer, Pluronic F127, swollen to various degrees with poly(propylene glycol). In addition, the density of silica spheres without a template was measured by two independent techniques: AFM and the Archimedes principle.

Spectroscopic investigations of spirooxazine and spiropyran incorporated in hybrid organic/inorganic silica particles

The incorporation of photochromic dyes in mesostructured silica particles and the subsequent incorporation of the particles in latex to create solid films with relatively large, yet controllable, thickness, was recently reported [N. Andersson, P. C. A. Alberius, J. Skov Pedersen, L. Bergstroem, Microporous and Mesoporous Materials, 2004, 72, 175-183; N. Andersson, P. Alberius, J. Oertegren, M. Lindgren, L. Bergstroem, J. Mater. Chem., 2005, in press.] As photochromic dyes, spirooxazine (SO) and spiropyran (SP) were used. The films are transparent in day-light at room temperature and become coloured upon UV exposure. The films have a potential for usage as display systems, optical switches and optical memory devices. The synthesis of the SO/SP doped silica particles and the making of solid films is briefly described, and the spectral properties of SO/SP in various environments - in the film, in solution, as pristine dye powder and as silica particle powder - were studied by absorbance and fluorescence measurements, including time-resolved fluorescence decay measurements. It was found that the spectral properties of the photo-chromic dyes in the films are similar to those observed in solution, indicating that they are well-dispersed in the organic phase of the silica particles, which, in turn, are well-dispersed in the latex film.

Spray Drying FunctionalizedMesostructured Colloids

An industrially viable production method is a prerequisite for the commercialization of templated mesostructured materials, e.g. as carriers of various functionalities in coatings, in the coatings of ink jet paper and liquid chromatography. A small pilot plant was constructed for the continuous production of well ordered mesostructured materials (>10g/h) that can easily be scaled to an industrial process. The silica colloids have a well controlled internal mesostructure and are spherical with a mean diameter of 1-5μm. The mesoscopic pores in the calcined materials are accessible to relatively large molecules; up to 25 % (by weight) of the cationic dye Janus Green B could be adsorbed from an aqueous solution. We have also demonstrated how optically functional silica colloids could be prepared in a one-pot synthesis by introducing different dyes into the precursor solution.