Silica coating magnetic nanoparticle-based silver enhancement immunoassay for rapid electrical detection of ricin toxin.

We developed a novel silica coating magnetic nanoparticle-based silver enhancement immunoassay (SEIA) for ricin toxin (RT) rapid electrical detection using interdigitated array microelectrodes (IDAMs) as electrodes. This novel system was developed by taking advantage of the separation and enrichment properties of magnetic nanoparticles (MNPs) and the catalytic properties of gold nanoparticles (GNPs). In this system, MNPs labeled with anti-ricin A chain antibody 6A6 were used to capture ricin and GNPs labeled with anti-ricin B chain antibody 7G7 were used as detectors. To enhance the electrical signal, the catalytic properties of GNPs were used to promote silver reduction. In the presence of ricin, a sandwich structure was formed which could be separated by a magnetic field. The sandwich complex was then transferred to IDAMs. The silver particles bridged the IDAM gaps and gave rise to an enhancing electrical signal that was detected by conductivity measurements. The results showed that the sensitivity of the SEIA for ricin electrical detection was five times greater than that of conventional colorimetric sandwich ELISA. Once the antibody used for detection was coated on the plates or MNPs, our system was three times more rapid than colorimetric sandwich ELISA. This rapid and sensitive detection system provides promising new potential for ricin detection.