title: Graphene-based rapid and highly-sensitive immunoassay for C-reactive protein using a smartphone-based colorimetric reader.
abstract: A novel immunoassay (IA) has been developed for human C-reactive protein (CRP), an important biomarker and tissue preserving factor for infection and inflammation. Graphene nanoplatelets (GNP) and 3-aminopropyltriethoxysilane (APTES) were admixed and covalently attached to a polystyrene based-microtiter plate (MTP), pretreated with KOH. The resulting surface served as a stable layer for the covalent attachment of the anti-human CRP antibody. The IA procedure was based on the one-step kinetics-based sandwich IA employing a minimum number of process steps, whereas the enzymatic reaction solution was monitored by a smartphone-based colorimetric reader. With a limit of detection and a limit of quantification of 0.07ngmL(-1) and 0.9ngmL(-1), it precisely detected CRP spiked in diluted human whole blood and plasma as well as the CRP levels in clinical plasma samples. The results obtained for "real-world" patient samples agreed well with those of the conventional immunosorbent assay and the clinically-accredited analyzer-based IA. The antibody-bound GNP-functionalized MTPs retained its original activity after 6 weeks of storage in 0.1M PBS, pH 7.4 at 4°C.
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: Sektion Experimentelle Anaesthesiologie, University Hospital Ulm, Albert Einstein Allee 23, 89081 Ulm, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Marion 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: D000906:Antibodies / Q000737:chemistry; D015374:Biosensing Techniques / Q000379:methods*; D002097:C-Reactive Protein / Q000302:isolation & purification*; D040421:Cell Phone; D003124:Colorimetry; D006108:Graphite / Q000737:chemistry*; D006801:Humans; D007118:Immunoassay / Q000379:methods*
chemical_list: D000906:Antibodies; D006108:Graphite; D002097:C-Reactive Protein
keywords: C-reactive protein; Graphene; One-step kinetics-based sandwich immunoassay; Smartphone-based colorimetric reader