Metal-enhanced chemiluminescence detection of C-reaction protein based on silver nanoparticle hybrid probes

A novel metal-enhanced chemiluminescence (MEC) signal tag was designed. By combining with a disposable immunosensor chip, an ultrasensitive immunoassay method was proposed for detection of C-reactive protein (CRP), an essential cerebrovascular disease marker. Two kinds of silver nanoparticle (AgNP) probes, DNA-hemin/DNA-A/biotin-DNA modified AgNPs (Probe A) and DNA-hemin/DNA-B modified AgNPs (Probe B) were prepared respectively. The MEC signal tag was formed by the link of Probe A and Probe B through the hybridization of DNA-A and DNA-B. The formed AgNP hybrid probes brought excellent CL signal amplification, due to the increased content of hemin molecules and the great MEC effect. The AgNP hybrid probes can be bound to the biotinylated antibody of sandwich immunocomplex for immunoassay of CRP. Under optimal conditions, the method showed a wide detection range of 7 × 10^-7 to 0.07 mg mL^-1 and a detection limit down to 0.05 ng mL^-1. The results obtained with clinical serum samples were in acceptable agreement with reference values. The AgNP hybrid probes as well as the MEC-based immunoassay method showed great potentials in early clinical diagnosis of cerebrovascular disease.