Magnetic Nanoparticle-Based Lateral Flow Immunochromatographic Strip as a Reporter for Rapid Detection of Melamine.

Magnetite nanoparticles (MNPs) Fe3O4 and r-Fe2O3 were surface-modified with poly(ethylene glycol) (PEG) in order to improve their specificity and bioactivity. PEG and the anti-MEL monoclonal antibody (mAb) were successfully immobilized on the surface of MNPs and characterized using FTIR, UV-Vis and TEM analyses. Surface modification of MNPs-PEG-mAb conjugates of a variety of sizes and magnetite types was employed to design and prepare labels for use in a lateral flow immunoassay (LFIA) to test whether the size of the conjugate can affect the performance of the assay. The results showed that the detection limit was mainly determined by the size of the MNPs-PEG-mAb conjugate. Under optimized conditions, a detection limit of 0.4 ppm for melamine was achieved using Fe2O3-PEG-mAb, which was almost 5-fold lower than that of the Fe3O4-PEG-mAb conjugate (2.2 ppm).