Sensitive detection of cardiac biomarker using ZnS nanoparticles as novel signal transducers.

C-reactive protein (CRP), a 115 kDa pentameric protein, is one of the important cardiac biomarkers that are indicative of coronary heart events. Sensitive detection of CRP in human serum is critical for the diagnosis of coronary heart disease. This work presents a sensitive sandwich immunoassay for the detection of CRP in human serum using zinc sulfide (ZnS) nanoparticles as novel fluorescence signal transducers. In this assay, monoclonal anti-CRP antibodies are used to capture CRP in human serum, and then the captured CRPs are incubated with biotinylated monoclonal anti-CRP and Neutravidin coated ZnS nanoparticle to form sandwich immunocomplexes. Quantification of CRP occurs when zinc ions released from ZnS nanoparticle labels are mixed with zinc-ion sensitive fluorescence indicator Fluozin-3 for fluorescence generation. The developed assay presents a detection limit around 10 pM and a detection range with more than two orders of magnitude.