title: Microarray immunoassay for phenoxybenzoic acid using polymer encapsulated Eu:Gd2O3 nanoparticles as fluorescent labels.
abstract: Currently, detection in microarray bioanalysis is based mainly on the use of organic dyes. To overcome photobleaching and spectral overlaps we applied a new type of fluorophore, crystalline europium-doped gadolinium oxide (Eu:Gd2O3) nanoparticles, as labels in immunoassay microarrays. The Eu:Gd2O3 nanoparticles synthesized by spray pyrolysis offer narrow red emission, large Stokes shift, photostable laser-induced fluorescence with a long lifetime (1 ms). The amino functionalization of the particles was achieved by poly(L-lysine) (PL) encapsulation. The formation of a stable PL shell was confirmed by TEM analysis, colloidal stability studies, and quantification of the surface reactive amino groups. The PL-encapsulated particles were covalently conjugated to antibodies and successfully applied as reporters in a competitive fluorescence microimmunoassay for phenoxybenzoic acid (PBA), a generic biomarker of human exposure to pyrethroid insecticides. Microarrays were fabricated by microcontact printing of BSA-PBA in line patterns (10 x 10 microm). Confocal fluorescence microscopy combined with internal standard (fluorescein) calibration was used for quantitative measurements. The microarray immunoassay demonstrated a limit of detection of 1.4 microg L(-1) PBA. This work suggests the potential application of lanthanide oxide nanoparticles as fluorescent probes in microarray and biosensor technology, immunodiagnostics, and high-throughput screening.
authors.affiliation: Department of Entomology, University of California Davis, Davis, California 95616, USA.
authors.forename: Mikaela
authors.initials: M
authors.lastname: Nichkova
authors.forename: Dosi
authors.initials: D
authors.lastname: Dosev
authors.forename: Shirley J
authors.initials: SJ
authors.lastname: Gee
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Hammock
authors.forename: Ian M
authors.initials: IM
authors.lastname: Kennedy
mesh_terms: D000906:Antibodies; D001565:Benzoates / Q000737:chemistry*; D005063:Europium / Q000737:chemistry*; D005682:Gadolinium / Q000737:chemistry*; D007118:Immunoassay / Q000295:instrumentation / Q000379:methods; D046228:Microarray Analysis / Q000379:methods*; D053758:Nanoparticles / Q000737:chemistry*; D010647:Phenyl Ethers / Q000737:chemistry*; D011107:Polylysine / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*
chemical_list: D000906:Antibodies; D001565:Benzoates; D010647:Phenyl Ethers; D011108:Polymers; C065921:4-carboxybiphenyl ether; D011107:Polylysine; D005063:Europium; C030581:gadolinium oxide; D005682:Gadolinium