Ultrasensitive electrochemical immunosensor based on horseradish peroxidase (HRP)-loaded silica-poly(acrylic acid) brushes for protein biomarker detection

We report an ultrasensitive electrochemical immunosensor designed for the detection of protein biomarkers using horseradish peroxidase (HRP)-loaded silica-poly(acrylic acid) brushes (SiO 2 -SPAABs) as labels. HRP could be efficiently and stably accommodated in the three-dimensional architecture of the SiO 2 -SPAABs and the SiO 2 -SPAABs-HRP exhibited high catalytic performance towards o -phenylenediamine (OPD) oxidation in the presence of H 2 O 2 , which resulted in significant differential pulse voltammetric (DPV) response change and color change. Using human IgG (HIgG) as a model analyte, a sandwich-type immunosensor was constructed. In particular, graphene oxide (GO) and SiO 2 -SPAABs-HRP were used to immobilize capture antibody (Ab 1 ) and bind a layer of detection antibody (Ab 2 ), respectively. The current biosensor exhibited a good linear response of HIgG from 100   pg/mL to 100   μg/mL with a detection limit of 50   pg/mL ( S / N =5). The sensitivity was 6.70-fold higher than the conventional enzyme-linked immunosorbent assays. The immunosensor results were validated through the detection of HIgG in serum samples.