title: A smartphone-based colorimetric reader for bioanalytical applications using the screen-based bottom illumination provided by gadgets.
abstract: A smartphone-based colorimetric reader (SBCR) was developed using a Samsung Galaxy SIII mini, a gadget (iPAD mini, iPAD4 or iPhone 5s), integrated with a custom-made dark hood and base holder assembly. The smartphone equipped with a back camera (5 megapixels resolution) was used for colorimetric imaging via the hood and base-holder assembly. A 96- or 24-well microtiter plate (MTP) was positioned on the gadget's screensaver that provides white light-based bottom illumination only in the specific regions corresponding to the bottom of MTP's wells. The pixel intensity of the captured images was determined by an image processing algorithm. The developed SBCR was evaluated and compared with a commercial MTP reader (MTPR) for three model assays: our recently developed human C-reactive protein sandwich enzyme-linked immunosorbent assay (ELISA), horseradish peroxidase direct ELISA, and bicinchoninic acid protein estimation assay. SBCR had the same precision, dynamic range, detection limit and sensitivity as MTPR for all three assays. With advanced microfabrication and data processing, SBCR will become more compact, lighter, inexpensive and enriched with more features. Therefore, SBCR with a remarkable computing power could be an ideal point-of-care (POC) colorimetric detection device for the next-generation of cost-effective POC diagnostics, immunoassays and diversified bioanalytical applications.
authors.affiliation: HSG-IMIT-Institut für Mikro- und Informationstechnik, Georges-Koehler-Allee 103, 79110 Freiburg, Germany; Laboratory for MEMS Applications, Department of Microsystems Engineering-IMTEK, University of Freiburg, Georges-Koehler-Allee 103, 79110 Freiburg, Germany. Electronic address: sandeep.kumar.vashist@hsg-imit.de.
authors.forename: Sandeep Kumar
authors.initials: SK
authors.lastname: Vashist
authors.affiliation: HSG-IMIT-Institut für Mikro- und Informationstechnik, Georges-Koehler-Allee 103, 79110 Freiburg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: van Oordt
authors.affiliation: Sektion Experimentelle Anaesthesiologie, University Hospital Ulm, Albert Einstein Allee 23, 89081 Ulm, Germany.
authors.forename: E Marion
authors.initials: EM
authors.lastname: Schneider
authors.affiliation: HSG-IMIT-Institut für Mikro- und Informationstechnik, Georges-Koehler-Allee 103, 79110 Freiburg, Germany; Laboratory for MEMS Applications, Department of Microsystems Engineering-IMTEK, University of Freiburg, Georges-Koehler-Allee 103, 79110 Freiburg, Germany.
authors.forename: Roland
authors.initials: R
authors.lastname: Zengerle
authors.affiliation: HSG-IMIT-Institut für Mikro- und Informationstechnik, Georges-Koehler-Allee 103, 79110 Freiburg, Germany; Laboratory for MEMS Applications, Department of Microsystems Engineering-IMTEK, University of Freiburg, Georges-Koehler-Allee 103, 79110 Freiburg, Germany.
authors.forename: Felix
authors.initials: F
authors.lastname: von Stetten
authors.affiliation: Innovative Chromatography Group, Irish Separation Science Cluster (ISSC), Department of Chemistry and Analytical, Biological Chemistry Research Facility (ABCRF), University College Cork, Cork, Ireland.
authors.forename: John H T
authors.initials: JH
authors.lastname: Luong
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation*; D003124:Colorimetry / Q000295:instrumentation*; D004797:Enzyme-Linked Immunosorbent Assay / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008029:Lighting / Q000295:instrumentation*; D063731:Mobile Applications; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D000068997:Smartphone
keywords: Bicinchoninic acid protein assay; Gadget; Immunoassay; Screen; Smartphone-based colorimetric readout