title: Silica colloidal crystals for enhanced fluorescence detection in microarrays.
abstract: Silica colloidal crystals were investigated for their potential as high surface area materials to enhance sensitivity over planar surfaces for microarrays using fluorescence detection. A relation was derived showing how crystal thickness and transmission, as well as colloid size, combine to determine the optically accessible surface area for enhancing sensitivity. Experimentally, crystals of 250-nm colloids were prepared with thicknesses determined by SEM to be 1.6, 4.2, and 11.0 microm. The material was sintered at 1000 degrees C to make it durable without affecting the crystalline structure, as confirmed by SEM. UV/visible spectrometry showed the depth of penetration (1/e) to be 8.4 microm at 488 nm for these materials. Fluorescein-labeled streptavidin and biotin were used as a model ligand-receptor pair. For the fluorescence measurements, biotin was covalently bonded to the silica surfaces, and the fluorescence was detected from the captured streptavidin-fluorescein. The observed fluorescence enhancement agreed well with the theory developed here. Compared to a planar surface, the colloidal crystal of 11.0 microm in thickness enhanced the fluorescence by nearly a factor of 80, with only a 0.3% increase in fluorescence background.
authors.affiliation: Department of Chemistry, University of Arizona, Tucson, Arizona 85721, USA.
authors.forename: Suping
authors.initials: S
authors.lastname: Zheng
authors.forename: Hui
authors.initials: H
authors.lastname: Zhang
authors.forename: Eric
authors.initials: E
authors.lastname: Ross
authors.forename: Thai Van
authors.initials: TV
authors.lastname: Le
authors.forename: Mary J
authors.initials: MJ
authors.lastname: Wirth
mesh_terms: D001710:Biotin; D003102:Colloids; D003460:Crystallization; D019793:Fluorescein; D005453:Fluorescence; D046228:Microarray Analysis / Q000379:methods* / Q000592:standards*; D012680:Sensitivity and Specificity; D012822:Silicon Dioxide; D019809:Streptavidin
chemical_list: D003102:Colloids; D001710:Biotin; D012822:Silicon Dioxide; D019809:Streptavidin; D019793:Fluorescein