A label-free electrochemical immunosensor based on encapsulated signal molecules in mesoporous silica-coated gold nanorods for ultrasensitive assay of procalcitonin.

For immobilization and signal amplification of the probes, it is feasible and promising by using porous nanomaterials as nanocarriers. Herein, a novel label-free electrochemical immmunosensor was efficiently designed for ultrasensitive detection of procalcitonin (PCT). The immunosensor was prepared by using porous silica-coated gold nanorods (Au NRs@m-SiO2) to load electroactive dye thionine (Thi) on the electrode surface. Apart from the improved electrical conductivity, the porous feature highly increased the loading amount of Thi to boost the detection signals, while the good biocompatibility and protective microenvironment are beneficial to the largely improved stability for the target. For quantification of PCT, the developed immunosensor exhibited a good linear relationship in the antigen concentration range of 0.001-100 ng mL-1 with an ultra-low limit of detection (LOD, 0.39 pg mL-1, S/N = 3). Moreover, the built platform was successfully applied to such assay in human serum samples. The research provides some valuable guidelines for clinical screening and diagnosis of other biomarkers.