title: Electrochemical immunoassay platform for high sensitivity protein detection based on redox-modified carbon nanotube labels.
abstract: We report a highly sensitive immunoassay protocol based on the use of redox-modified multi-walled carbon nanotubes (MWNTs) as electrochemical labels. The MWNTs were coated with methylene blue (MB) at an optically-determined loading of 3.41 × 10(-3) mol g(-1), and were then attached to secondary antibodies (Ab(2)) by adsorption. As a model analyte mouse IgG was collected by primary antibody (Ab(1))-coated magnetic beads. Following binding of the MB-MWNT-Ab(2) conjugates, IgG could be measured by MB reduction. Using differential pulse voltammetry for quantification, IgG was calibrated with a dynamic range of 0.1 pg mL(-1) to 100 pg mL(-1). Given the different possible Ab(1)-MB-MWNT-Ab(2) orientations on the magnetic beads, it was likely that not all the MB communicated with the electrode. A greater quantity of MB could be accessed by using the Fe(CN)(6)(3-/4-) redox couple as a solution phase mediator. This enabled us to lower the dynamic range down to 5 fg mL(-1) to 100 fg mL(-1).
authors.affiliation: School of Bioresources and Technology, King Mongkut's University of Technology Thonburi, Bangkhuntien Campus, Bangkok, 10150, Thailand.
authors.forename: Wilanee
authors.initials: W
authors.lastname: Chunglok
authors.forename: Porntip
authors.initials: P
authors.lastname: Khownarumit
authors.forename: Patsamon
authors.initials: P
authors.lastname: Rijiravanich
authors.forename: Mithran
authors.initials: M
authors.lastname: Somasundrum
authors.forename: Werasak
authors.initials: W
authors.lastname: Surareungchai
mesh_terms: D000818:Animals; D000906:Antibodies / Q000737:chemistry / Q000276:immunology; D055664:Electrochemical Techniques / Q000379:methods*; D004566:Electrodes; D005292:Ferricyanides / Q000737:chemistry; D007118:Immunoassay / Q000379:methods*; D007074:Immunoglobulin G / Q000032:analysis* / Q000276:immunology; D008751:Methylene Blue / Q000737:chemistry; D051379:Mice; D037742:Nanotubes, Carbon / Q000737:chemistry*; D010084:Oxidation-Reduction
chemical_list: D000906:Antibodies; D005292:Ferricyanides; D007074:Immunoglobulin G; D037742:Nanotubes, Carbon; C007931:hexacyanoferrate III; D008751:Methylene Blue