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Release and molecular transport of cationic and anionic fluorescent molecules in mesoporous silica spheres
Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
2008 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, no 19, 11096-11102 p.Article in journal (Refereed) Published
Abstract [en]

We describe here a method for study of bulk release and local molecular transport within mesoporous silica spheres. We have analyzed the loading and release of charged fluorescent dyes from monodisperse mesoporous silica (MMS) spheres with an average pore size of 2.7 nm. Two different fluorescent dyes, one cationic and one anionic, have been loaded into the negatively charged porous material and both the bulk release and the local molecular transport within the MMS spheres have been quantified by confocal laser scanning microscopy. Analysis of the time-dependent release and the concentration profiles of the anionic dye within the spheres show that the spheres are homogeneous and that the release of this nonadsorbing dye follows a simple diffusion-driven process. The concentration of the cationic dye varies radially within the MMS spheres after loading; there is a significantly higher concentration of the dye close to the surface of the spheres (forming a “skin”) compared to that at the core. The release of the cationic dye is controlled by diffusion after an initial period of rapid release. The transport of the cationic dye within the MMS spheres of the dye from the core to near the surface is significantly faster compared to the transport within the surface “skin”. A significant fraction of the cationic dye remains permanently attached to the negatively charged walls of the MMS spheres, preferentially near the surface of the spheres. Relating bulk release to the local molecular transport within the porous materials provides an important step toward the design of new concepts in controlled drug delivery and chromatography.

Place, publisher, year, edition, pages
2008. Vol. 24, no 19, 11096-11102 p.
Identifiers
URN: urn:nbn:se:su:diva-15440DOI: 10.1021/la801179vISI: 000259673500084OAI: oai:DiVA.org:su-15440DiVA: diva2:181960
Available from: 2008-12-02 Created: 2008-12-02 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Harnessing Mesoporous Spheres - transport studies and biotechnological applications
Open this publication in new window or tab >>Harnessing Mesoporous Spheres - transport studies and biotechnological applications
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Applications in controlled release and delivery calls for a good understanding of molecular transport within the carrier material and the dominating release mechanisms. It is clear that a better understanding of hindered transport and diffusion of guest molecules is important when developing new porous materials, e.g., surfactant templated silica spheres, for biotechnological applications. Confocal laser scanning microscopy was used to quantify the bulk release and intraparticle transport of small charged fluorescent dyes, and fluorescently-tagged neutral dextran, from mesoporous silica spheres. The time dependent release and the concentration profiles within the spheres have been used to analyze the release mechanisms using appropriate models. While the small, non-adsorbing anionic dye is released following a simple diffusion driven process, the concentration of the cationic dye varies radially within the spheres after loading. The release of the cationic dye is controlled by diffusion after an initial period of rapid release, which could be due to a significant fraction of the cationic dye that remains permanently attached to the negatively charged walls of the mesoporous silica spheres. The diffusion of dextran and the resulting flat concentration profiles could be related to the complex structural feature of the cylindrical pores close to the surface, and a possible conformational change of the dextran with the concentration. The stability and leaching of a catalytic enzyme, lipase, immobilized in hydrophobilized mesoporous support has also been quantified. Colloidal monodisperse mesoporous silica spheres were synthesized and transmission electron microscopy showed that the inner pore structure display a radially extending pores. The mesoporous spheres were used as solid supports for a lipid membrane incorporated with a multi-subunit redox-driven proton pump, which was shown to remain functional.

Place, publisher, year, edition, pages
Stockholm: Department of Physical, Inorganic and Structural Chemistry, Stockholm University, 2009. 69 p.
Keyword
Mesoporous, spheres, particles, CLSM, TEM, controlled-release, molecular transport, lipid membrane, enzyme, intraparticle, lipase, solid support
National Category
Inorganic Chemistry
Research subject
Materials Science
Identifiers
urn:nbn:se:su:diva-27797 (URN)978-91-7155-898-5 (ISBN)
Public defence
2009-09-02, Nordenskiöldsalen, Geovetenskapens hus, Svante Arrhenius väg 8 C, Stockholm, 10:00 (English)
Opponent
Supervisors
Projects
Synthesis, functionalisation and controlled release of mesoporous materials
Available from: 2009-05-27 Created: 2009-05-19 Last updated: 2009-05-20Bibliographically approved

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