title: Microtextured substrates and microparticles used as in situ lenses for on-chip immunofluorescence amplification.
abstract: We propose a concept for enhancing the fluorescent detection signal of on-chip immunoassays by using three-dimensional 3 and 8 μm size microtextured structures as substrates for the assay, which allows exploitation of a large number of fluorophores within the focal plane of an optical microscope for detection. Additionally, we demonstrate the use of 3 and 9.75 μm dielectric microparticles, respectively, as in situ lenses on the 3 and 8 μm microstructures, respectively, for further enhancement of the optical signal. In our model system, the fluorescent complex is formed on (3-aminopropyl)triethoxysilane microstructures and we use carboxyl-functionalized melamine microparticles as the in situ lenses. Mouse IgG diluted in phosphate-buffered saline is used as model target antigen and can be easily detected down to a concentration of 2 ng/mL thanks to these approaches. Also, we present a detailed two-dimensional numerical study of the light propagation through a dielectric microparticle using the finite element method, providing key insight into the signal amplification mechanism of a microlens, and point out its advantageous use in microfluidic assays.
authors.affiliation: Laboratory of Microsystems, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland. hui.yang@epfl.ch
authors.forename: Hui
authors.initials: H
authors.lastname: Yang
authors.forename: Martin A M
authors.initials: MA
authors.lastname: Gijs
mesh_terms: D000818:Animals; D055910:Antibodies, Immobilized / Q000276:immunology; D005456:Fluorescent Dyes / Q000737:chemistry; D007118:Immunoassay / Q000295:instrumentation / Q000379:methods*; D007074:Immunoglobulin G / Q000032:analysis*; D051379:Mice; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation / Q000379:methods; D008858:Microscopy, Phase-Contrast; D008863:Microspheres; D019904:Polymethyl Methacrylate / Q000737:chemistry; D011437:Propylamines; D012821:Silanes / Q000737:chemistry; D013379:Substrate Specificity; D014227:Triazines / Q000737:chemistry
chemical_list: D055910:Antibodies, Immobilized; D005456:Fluorescent Dyes; D007074:Immunoglobulin G; D011437:Propylamines; D012821:Silanes; D014227:Triazines; D019904:Polymethyl Methacrylate; C477625:amino-propyl-triethoxysilane; C011907:melamine