Determination of trace human chorionic gonadotropin by using multiwall carbon nanotubes as phosphorescence labeling reagent

Taking advantage of the cutting effect of the strong oxidation of benzoyl peroxide [(C6H5CO)(2)O-2] on the end of multiwall carbon nanotubes (MWNTs) to obtain water-soluble multiwall nanotubes (MWNTs') and the spiking effect of polyacrylamide (PA) on the room temperature phosphorescence (RIP) of MWNTs', a new phosphorescent labeling reagent, MWNTs'-PA, has been developed in this study. The product beta-Ab(HCG)-MWNTs'-PA obtained by MWNTs'-PA labeling human chorionic gonadotropin-beta-subunit three-dimensional core monoclonal antibody (beta-Ab(HCG)) not only could maintain good RTP characteristics of MWNTs' but also could take specific immunoreaction with beta-HCG to form beta-HCG-beta-Ab(HCG)-MWNTs'-PA, resulting in the increase of MWNTs' RTP signal. Thus, a new solid substrate room temperature phosphorescence immunoassay (SSRTPIA) for the determination of beta-HCG has been established. The limits of detection (LODs) of the new method were 0.021 pg spot(-1) for the direct way at 447/615 nm (lambda(max)(ex)/lambda(max)(ex)) and 0.016 pg spor(-1) for the sandwich way at 447/614 nm (lambda(max)(ex)/lambda(max)(ex)). This sensitive, accurate, and precise method was used to determine beta-HCG and diagnose human diseases by the direct way or the sandwich way, with the results coinciding with those obtained by chemiluminescence immunoassay. Meanwhile, the mechanisms of MWNTs' labeling beta-Ab(HCG) and determining beta-(HCG) are also discussed. (c) 2012 Elsevier Inc. All rights reserved.