title: Nanoencapsulated microcrystalline particles for superamplified biochemical assays.
abstract: We report on the preparation and utilization of a novel class of particulate labels based on nanoencapsulated organic microcrystals with the potential to create highly amplified biochemical assays. Labels were constructed by encapsulating microcrystalline fluorescein diacetate (FDA; average size of 500 nm) within ultrathin polyelectrolyte layers of poly(allylamine hydrochloride) and poly(sodium 4-styrenesulfonate) via the layer-by-layer technique. Subsequently, the polyelectrolyte coating was used as an "interface" for the attachment of anti-mouse antibodies through adsorption. A high molar ratio of fluorescent molecules present in the microcrystal core to biomolecules on the particle surface was achieved. The applicability of the microcrystal-based label system was demonstrated in a model sandwich immunoassay for mouse immunoglobulin G detection. Following the immunoreaction, the FDA core was dissolved by exposure to organic solvent, leading to the release of the FDA molecules into the surrounding medium. Amplification rates of 70-2000-fold (expressed as an increase in assay sensitivity) of the microcrystal label-based assay compared with the corresponding immunoassay performed with direct fluorescently labeled antibodies are reported. Our approach provides a general and facile means to prepare a novel class of biochemical assay labeling systems. The technology has the potential to compete with enzyme-based labels as it does not require long incubation times, thus speeding up bioaffinity tests.
authors.affiliation: Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, SAR. trau@ust.hk
authors.forename: Dieter
authors.initials: D
authors.lastname: Trau
authors.forename: Wenjun
authors.initials: W
authors.lastname: Yang
authors.forename: Matthias
authors.initials: M
authors.lastname: Seydack
authors.forename: Frank
authors.initials: F
authors.lastname: Caruso
authors.forename: Nai-Teng
authors.initials: NT
authors.lastname: Yu
authors.forename: Reinhard
authors.initials: R
authors.lastname: Renneberg
mesh_terms: D000818:Animals; D000906:Antibodies / Q000737:chemistry; D004586:Electrophoresis / Q000379:methods; D016650:Fluorescein-5-isothiocyanate / Q000737:chemistry; D005452:Fluoresceins / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry*; D015200:Fluoroimmunoassay / Q000379:methods*; D007074:Immunoglobulin G / Q000032:analysis* / Q000737:chemistry; D051379:Mice; D008832:Microchemistry / Q000379:methods; D008855:Microscopy, Electron, Scanning; D036103:Nanotechnology / Q000379:methods
chemical_list: D000906:Antibodies; D005452:Fluoresceins; D005456:Fluorescent Dyes; D007074:Immunoglobulin G; D016650:Fluorescein-5-isothiocyanate; C018506:diacetylfluorescein