title: Multi-spot, label-free immunoassay on reflectionless glass.
abstract: Biosensing platforms that combine high sensitivity, operational simplicity and affordable costs find wide application in many fields, including human diagnostics, food and environmental monitoring. In this work, we introduce a label-free biosensing chip made of glass with a single anti-reflective layer of SiO2. This common and economic material coated by a multi-functional copolymer based on dimethylacrylamide enables the detection even in turbid media. The copolymer coating provides covalent immobilization of antibodies onto the surface and prevents the non-specific adsorption of analytes and matrix constituents. The specific capture of target compounds yields a local increase of surface reflectivity measured by a simple imaging system. Chip design and quantitative interpretation of the data are based on a theoretical optical model. This approach enables the multiplex detection of biomolecular interactions with state-of-the-art sensitivity and minimal instrumental complexity. The detection performance is demonstrated by characterizing the interaction between human growth hormone in solution and the corresponding antibodies immobilized on the sensing surface, both in buffer and human serum, obtaining a clear signal for concentrations as small as 2.8 ng/ml.
authors.affiliation: Proxentia S.r.l., 20135 Milano, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Salina
authors.affiliation: Department of Medical Biotechnology and Translational Medicine, Università degli Studi di Milano, 20090 Segrate, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Giavazzi
authors.affiliation: Department of Medical Biotechnology and Translational Medicine, Università degli Studi di Milano, 20090 Segrate, Italy.
authors.forename: Roberta
authors.initials: R
authors.lastname: Lanfranco
authors.affiliation: Department of Medical Biotechnology and Translational Medicine, Università degli Studi di Milano, 20090 Segrate, Italy.
authors.forename: Erica
authors.initials: E
authors.lastname: Ceccarello
authors.affiliation: Istituto di Chimica del Riconoscimento Molecolare - C.N.R., 20131 Milano, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Sola
authors.affiliation: Istituto di Chimica del Riconoscimento Molecolare - C.N.R., 20131 Milano, Italy.
authors.forename: Marcella
authors.initials: M
authors.lastname: Chiari
authors.affiliation: Istituto di Neuroscienze - C.N.R., 20129 Milano, Italy.
authors.forename: Bice
authors.initials: B
authors.lastname: Chini
authors.affiliation: Department of Medical Biotechnology and Translational Medicine, Università degli Studi di Milano, 20090 Segrate, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Cerbino
authors.affiliation: Department of Medical Biotechnology and Translational Medicine, Università degli Studi di Milano, 20090 Segrate, Italy. Electronic address: tommaso.bellini@unimi.it.
authors.forename: Tommaso
authors.initials: T
authors.lastname: Bellini
authors.affiliation: Department of Medical Biotechnology and Translational Medicine, Università degli Studi di Milano, 20090 Segrate, Italy. Electronic address: marco.buscaglia@unimi.it.
authors.forename: Marco
authors.initials: M
authors.lastname: Buscaglia
mesh_terms: D000906:Antibodies / Q000276:immunology; D015374:Biosensing Techniques / Q000295:instrumentation*; D020099:Coated Materials, Biocompatible / Q000138:chemical synthesis; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005898:Glass / Q000737:chemistry*; D019382:Human Growth Hormone / Q000097:blood* / Q000276:immunology; D006801:Humans; D007118:Immunoassay / Q000295:instrumentation*; D008027:Light; D010783:Photometry / Q000295:instrumentation*; D015203:Reproducibility of Results; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity; D012822:Silicon Dioxide / Q000737:chemistry*; D013194:Staining and Labeling
chemical_list: D000906:Antibodies; D020099:Coated Materials, Biocompatible; D019382:Human Growth Hormone; D012822:Silicon Dioxide
keywords: Human growth hormone; Optical biosensors; Point of care; Protein microarrays; Reflective Phantom Interface