This study proposes a potentially rapid and effective immunoassay using antibody-platinum nanoparticles (Ab-PtNPs) conjugates as a message molecule and a flatbed scanner for the optical scanning and measuring of the immuno-reaction signal. The proposed immunoassay is a sandwich-type immunoassay (three-layer format) along with a silver enhancement reaction, and a signal amplification method was introduced to magnify the detected signal. The signal was the grayscale corresponded to the immuno-reaction, which determined the detection limit and reaction time. Results showed that the rapid silver precipitation phenomenon was catalyzed by Ab-PtNPs conjugates. The color change during the reaction was readily observed by the naked eye and analyzed by an optical flatbed scanner. The relationship between sample concentration and grayscale of signal is discussed. The detection limit (sandwich format assay) for the sample antigen was 0.1 ng/mL which is superior to the detection limit achieved via Au and Ag nanoparticles (AuNPs and AgNPs). Using an optical flatbed scanner, Ab-PtNPs conjugates and a silver enhancement reaction, a novel immunoassay has been constructed.
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