A novel immunoassay using platinum nanoparticles, silver enhancement and a flatbed scanner

This study reports a potentially rapid and convenient immunoassay using antibody-platinum nanoparticle (Ab-PtNPs) conjugates as a reporter molecule and a flatbed scanner for detecting immuno-reaction and measuring of the immuno-reaction signal. This study was based on the sandwich immunoassay (three-layer format) which contained a primary antibody, test antigens and a secondary antibody. The results showed that the silver precipitation phenomenon was catalyzed by Ab-PtNPs conjugates. The changing color of reaction could easily be observed by naked eye or scanner. The silver enhancement reaction, a signal amplification method in which silver ions are reduced to silver metal, is introduced to magnify the detection signal. The relationship between sample concentration and detection signal was discussed. And the detection limit (sandwich assay) for the sample antigen was 10-1 ng/mL. Using a flatbed scanner, Ab-PtNPs conjugates and a silver enhancement reaction, a new immunoassay is constructed.