Sensitive immunosensor for benzo[a]pyrene detection based on dual amplification strategy of PAMAM dendrimer and amino-modified methylene blue/SiO2 core–shell nanoparticles

A novel electrochemical immunosensor for sensitive detection of benzo[a]pyrene (BaP) is constructed using poly(amido amine) (PAMAM) dendrimer and functionalized methylene blue/SiO2 core–shell nanoparticle (MB/SiO2) loaded with horseradish peroxidase (HRP) and HRP-secondary antibody (HRP-Ab2). Greatly enhanced sensitivity for BaP analysis is based on a dual signal amplification strategy. Firstly, the gold electrode (GE) was amino-functioned by electropolymerization of a novel compound, 2-amino-5,2′:5′2′′-terthiophene, followed by the modification of G 2.0 PAMAM dendrimer to amplify functional groups on the substrate and thus enhance the immobilization capacity of BaP antigen (BaP-Ag). Secondly, amino-functionalized MB/SiO2 was used to load HRP and HRP-Ab2, and the resulting nanostructure (HRP-MB/SiO2-Ab2) was applied as the detection label for the immunosensor. The proposed immunosensor exhibited a relatively wide linear response between 0.01 and 2.0 ng/mL with a detection limit of 6 pg/mL. This amplification strategy shows excellent promise for environmental monitoring of some pollutants and a potential application in the immunosensor.