title: Electrochemical coding for multiplexed immunoassays of proteins.
abstract: An electrochemical immunoassay protocol for the simultaneous measurements of proteins, based on the use of different inorganic nanocrystal tracers is described. The multiprotein electrical detection capability is coupled to the amplification feature of electrochemical stripping transduction (to yield fmol detection limits) and with an efficient magnetic separation (to minimize nonspecific adsorption effects). The multianalyte electrical sandwich immunoassay involves a dual binding event, based on antibodies linked to the nanocrystal tags and magnetic beads. Carbamate linkage is used for conjugating the hydroxyl-terminated nanocrystals with the secondary antibodies. Each biorecognition event yields a distinct voltammetric peak, whose position and size reflects the identity and level, respectively, of the corresponding antigen. The concept is demonstrated for a simultaneous immunoassay of beta(2)-microglobulin, IgG, bovine serum albumin, and C-reactive protein in connection with ZnS, CdS, PbS, and CuS colloidal crystals, respectively. These nanocrystal labels exhibit similar sensitivity. Such electrochemical coding could be readily multiplexed and scaled up in multiwell microtiter plates to allow simultaneous parallel detection of numerous proteins or samples and is expected to open new opportunities for protein diagnostics and biosecurity.
authors.affiliation: Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, New Mexico 88003, USA.
authors.forename: Guodong
authors.initials: G
authors.lastname: Liu
authors.forename: Joseph
authors.initials: J
authors.lastname: Wang
authors.forename: Jeonghwan
authors.initials: J
authors.lastname: Kim
authors.forename: M Rasul
authors.initials: MR
authors.lastname: Jan
authors.forename: Greg E
authors.initials: GE
authors.lastname: Collins
mesh_terms: D000818:Animals; D002097:C-Reactive Protein / Q000032:analysis / Q000737:chemistry; D019187:Cadmium Compounds / Q000737:chemistry; D002219:Carbamates / Q000737:chemistry; D002417:Cattle; D003102:Colloids / Q000737:chemistry; D003300:Copper / Q000737:chemistry; D004563:Electrochemistry; D007118:Immunoassay / Q000379:methods; D007074:Immunoglobulin G / Q000737:chemistry; D007854:Lead / Q000737:chemistry; D049329:Nanostructures / Q000737:chemistry; D011506:Proteins / Q000032:analysis / Q000737:chemistry*; D012680:Sensitivity and Specificity; D012710:Serum Albumin, Bovine / Q000032:analysis / Q000737:chemistry; D013440:Sulfides / Q000737:chemistry; D013499:Surface Properties; D017967:Zinc Compounds / Q000737:chemistry; D001613:beta 2-Microglobulin / Q000737:chemistry
chemical_list: D019187:Cadmium Compounds; D002219:Carbamates; D003102:Colloids; D007074:Immunoglobulin G; D011506:Proteins; D013440:Sulfides; D017967:Zinc Compounds; D001613:beta 2-Microglobulin; C034939:cadmium sulfide; C018391:lead sulfide; D012710:Serum Albumin, Bovine; D007854:Lead; D003300:Copper; D002097:C-Reactive Protein; C017846:cupric sulfide; C031238:zinc sulfide