title: Electrophoretic build-up of multi nanoparticle array for a highly sensitive immunoassay.
abstract: One of the challenges in shrinking immunoassays to smaller sizes is to immobilize the biological molecules to nanometer-scaled spots. To overcome this complication, we have employed a particle-based immunoassay to create a nanostructured platform with a regular array of sensing elements. The technique makes use of an electrophoretic particle entrapment system (EPES) to immobilize nanoparticles that are coated with biological reagents into wells using a very small trapping potential. To provide useful information for controlling the trapping force and optimal design of the nanoarray, electrophoretic trapping of a nanoparticle was modeled numerically. The trapping efficiency, defined as the fraction of wells occupied by a single particle, was 91%. The performance of the array was demonstrated with a competitive immunoassay for a small molecule analyte, 3-phenoxybenzoic acid (214.2 g mole(-1)). The limit of detection determined with a basic fluorescence microscope was 0.006 μg l(-1) (30 pM); this represented a sixteen-fold improvement in sensitivity compared to a standard 96-well plate-based ELISA; the improvement was attributed to the small size of the sample volume and the presence of light diffraction among factors unique to this structure. The EPES/nanoarray system promises to offer a new standard in applications that require portable, point-of-care and real-time monitoring with high sensitivity.
authors.affiliation: Department of Mechanical and Aerospace Engineering, University of California, Davis, California, CA 95616, USA.
authors.forename: Jin-Hee
authors.initials: JH
authors.lastname: Han
authors.forename: Hee-Joo
authors.initials: HJ
authors.lastname: Kim
authors.forename: L
authors.initials: L
authors.lastname: Sudheendra
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Hass
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: D001704:Biopolymers / Q000032:analysis*; D015374:Biosensing Techniques / Q000295:instrumentation*; D004586:Electrophoresis / Q000379:methods*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007118:Immunoassay / Q000295:instrumentation*; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013050:Spectrometry, Fluorescence / Q000295:instrumentation*
chemical_list: D001704:Biopolymers