Fabrication of multiwalled carbon nanotubes-magnetite nanocomposite as an effective ultra-sensing platform for the early screening of nasopharyngeal carcinoma by luminescence immunoassay.

The hybrid nanocomposite that consists of multiwalled carbon nanotubes (MWCNTs) and magnetite (Fe₃O4) was fabricated by chemical co-precipitation method. Briefly, CNTs were oxidized with acids to form carboxylic group and then co-precipitated with Fe₃O4 to form CNT-Fe₃O4 nanocomposites. The nanocomposites were characterized by SEM, HRTEM, XRD, FTIR X-ray photoelectron spectrometry (XPS) and SQUID. The XRD results indicated the high crystallinity of Fe₃O₄ nanoparticles with spinel structure and the transmission electron microscope images depicted the intercalated iron oxide magnetic particles on the surface of CNTs. The MWCNTs-Fe₃O₄ was applied as a sensing interface to perform luminescence enzyme immunoassays. Firstly, EBNA-1 antigen was immobilized onto the carboxyl group functionalized MWCNTs-Fe₃O₄, followed by binding with anti-EBNA-1 IgA antibodies. The diluted secondary antibodies (anti-human IgA-HRP) were then added to the CNTs/Fe₃O₄-PEG-EBNA-1-anti-EBV IgA ab complex and act as a catalyst to produce a visible light upon reaction with the substrate luminol. The formed RLU is proportional to the amount of IgA anti-EBV antiobodies on the MWCNTs. The detection limit of proposed CNTs/Fe₃O₄ based luminescence enzyme immunoassay was in the order of 0.00128 EU/mL (1:100,000 fold dilution) for the detection of anti-EBV IgA antibodies, whereas the commercial ELISA and magnetic beads' assay was accounted for up to the dilution fold of 1000 (i.e., 0.128 EU/mL). The initial findings showed that CNTs/Fe₃O₄ nanocomposites have a great potential in luminescent enzyme immunoassays and could be used as a sensing platform for the early screening of nasopharyngeal carcinoma.