title: Diffusion in a sol-gel-derived medium with a view toward biosensor applications.
abstract: Time-resolved fluorescence anisotropy and fluorescence recovery after photobleaching were applied to study the diffusion of dyes and a fluorescence-labeled enzyme in a sol-gel-derived medium. This type of medium exhibits attractive properties such as robustness, low processing temperature, high porosity, large internal surface area, and can act as protective immobilization media for biologically active molecules. This makes it a suitable candidate for biosensor applications. The glasslike nature and good optical quality allows for light addressable entities to be incorporated and accessed using spectroscopy. This type of matrix, once formed, can be anything from an ordered gel to a robust glassy block depending on the aging process. In this work we apply confocal microscopy and time-resolved fluorescence techniques to study both rotational and lateral diffusion with aging time within a silica sol-gel derived monolith. An enzyme, horseradish peroxidase, was labeled with Alexa Fluor 488 and rotation related to both the enzyme and the probe monitored during the matrix aging process. Diffusion coefficients of between ca. 0.5 x 10(-7) and 4 x 10(-7) cm2 s(-1) were obtained from preliminary FRAP measurements of fluorescein and correlated to differences in the catalytic activity of HRP incorporated in the monolith.
authors: Departamento de Física, Universidade do Minho, 4710-057 Braga, Portugal. graham@fisica.uminho.pt
authors: Graham
authors: G
authors: Hungerford
authors: Ana
authors: A
authors: Rei
authors: M Isabel C
authors: MI
authors: Ferreira
authors: Klaus
authors: K
authors: Suhling
authors: Carolyn
authors: C
authors: Tregidgo
mesh_terms: D015374:Biosensing Techniques; D002384:Catalysis; D004058:Diffusion; D019793:Fluorescein / Q000737:chemistry; D005454:Fluorescence Polarization; D036681:Fluorescence Recovery After Photobleaching; D005456:Fluorescent Dyes / Q000737:chemistry; D006735:Horseradish Peroxidase / Q000737:chemistry*; D044367:Phase Transition; D058428:Silica Gel; D012822:Silicon Dioxide / Q000737:chemistry*
chemical_list: D005456:Fluorescent Dyes; D058428:Silica Gel; D012822:Silicon Dioxide; D006735:Horseradish Peroxidase; D019793:Fluorescein