title: A sensitive magnetic nanoparticle-based immunoassay of phosphorylated acetylcholinesterase using protein cage templated lead phosphate for signal amplification with graphite furnace atomic absorption spectrometry detection.
abstract: We developed a new magnetic nanoparticle sandwich-like immunoassay using protein cage nanoparticles (PCN) for signal amplification together with graphite furnace atomic absorption spectrometry (GFAAS) for the quantification of an organophosphorylated acetylcholinesterase adduct (OP-AChE), the biomarker of exposure to organophosphate pesticides (OPs) and nerve agents. OP-AChE adducts were firstly captured by titanium dioxide coated magnetic nanoparticles (TiO2-MNPs) from the sample matrixes through metal chelation with phospho-moieties, and then selectively recognized by anti-AChE antibody labeled on PCN which was packed with lead phosphate in its cavity (PCN-anti-AChE). The sandwich-like immunoreaction was performed among TiO2-MNPs, OP-AChE and PCN-anti-AChE to form a TiO2-MNP/OP-AChE/PCN-anti-AChE immunocomplex. The complex could be easily isolated from the sample solution with the help of magnet, and the released lead ions from PCN were detected by GFAAS for the quantification of OP-AChE. Greatly enhanced sensitivity was achieved because PCN increased the amount of metal ions in the cavity of each apoferritin. The proposed immunoassay yielded a linear response over a broad range of OP-AChE concentrations from 0.01 nM to 2 nM, with a detection limit of 2 pM, which has enough sensitivity for monitoring of low-dose exposure to OPs. This new method showed an acceptable stability and reproducibility and was validated with OP-AChE spiked human plasma.
authors.affiliation: Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, College of Chemistry, Central China Normal University, Wuhan 430079, P. R. China. liangpei@mail.ccnu.edu.cn annie.du@wsu.edu.
authors.forename: Pei
authors.initials: P
authors.lastname: Liang
authors.affiliation: Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, College of Chemistry, Central China Normal University, Wuhan 430079, P. R. China. liangpei@mail.ccnu.edu.cn annie.du@wsu.edu.
authors.forename: Caiyan
authors.initials: C
authors.lastname: Kang
authors.affiliation: Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, College of Chemistry, Central China Normal University, Wuhan 430079, P. R. China. liangpei@mail.ccnu.edu.cn annie.du@wsu.edu.
authors.forename: Enjian
authors.initials: E
authors.lastname: Yang
authors.affiliation: School of Mechanical and Materials Engineering, PO Box 642920 and Washington State University, Pullman, WA 99164, USA.
authors.forename: Xiaoxiao
authors.initials: X
authors.lastname: Ge
authors.affiliation: School of Mechanical and Materials Engineering, PO Box 642920 and Washington State University, Pullman, WA 99164, USA.
authors.forename: Dan
authors.initials: D
authors.lastname: Du
authors.affiliation: School of Mechanical and Materials Engineering, PO Box 642920 and Washington State University, Pullman, WA 99164, USA.
authors.forename: Yuehe
authors.initials: Y
authors.lastname: Lin
mesh_terms: D000110:Acetylcholinesterase / Q000032:analysis*; D006108:Graphite / Q000737:chemistry*; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D007854:Lead / Q000737:chemistry*; D057230:Limit of Detection; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D010750:Phosphoproteins / Q000032:analysis*; D013054:Spectrophotometry, Atomic / Q000379:methods*; D014025:Titanium / Q000737:chemistry
chemical_list: D058185:Magnetite Nanoparticles; D010750:Phosphoproteins; C009495:titanium dioxide; D007854:Lead; C036682:lead phosphate; D006108:Graphite; D014025:Titanium; D000110:Acetylcholinesterase