Electrochemical immunoassay for procalcitonin antigen detection based on signal amplification strategy of multiple nanocomposites

Procalcitonin, as a medium of inflammation, has become a new marker of the identification of severe bacterial infections in recent years and has received high attention due to its most ideal diagnostic indicators of specificity with major types of organism systemic inflammation of bacterial infection in the early stages. Thus, a novel method for the determination of procalcitonin (PCT) was developed based on a sandwich-type electrochemical immunosensor, which combined a simple immunosensor array as well as an effectively designed trace tag. The immunosensor was fabricated by layer-by-layer coating graphene (GC), carbon nanotubes (MWCNTs), chitosan (CS), glutaraldehyde (GA) composite on the working electrode, which can increase the electronic transfer rate and improve the surface area to capture a large number of primary antibodies (Ab1). The trace tag was prepared by loading high-content signal horseradish peroxidase labeled secondary PCT antibody (HRP-Ab2) with AuNPs, which were coated with mesoporous silica nanoparticles (MCM-41) through thionine linking. In comparison with conventional methods, the proposed immunosensor for PCT provided a better linear response range from 0.01 to 350 ng/mL and a lower limit of detection (LOD) of 0.5 pg/mL under optimal experimental conditions. In addition, the immunosensor exhibited convenience, low cost, rapidity, good specificity, acceptable stability and reproducibility. Moreover, satisfactory results were obtained for the determination of PCT in real human serum samples, indicating that the developed immunoassay has the potential to find application in clinical detection of PCT and other tumor markers as an alternative approach.