An electrochemiluminescence immunosensor for thyroid stimulating hormone based on polyamidoamine-norfloxacin functionalized Pd–Au core–shell hexoctahedrons as signal enhancers

In this work, a novel polyamidoamine-norfloxacin (PAMAM-NFLX) complex and core-shell Pd-Au hexoctahedrons (Pd@Au HOHs) as enhancers are employed for development of a sensitive sandwich-type electrochemiluminescence (ECL) immunosensor to detect thyroid stimulating hormone (TSH). Here, norfloxacin (NFLX) is decorated abundantly on the surface of polyamidoamine (PAMAM) dendrimer via amide linkage to form PAMAM-NFLX complex. Thus, the resultant PAMAM-NFLX can serve as a novel co-reactant to efficiently amplify the ECL signal of peroxydisulfate-oxygen (S2O8(2-)-O2) system. Pd@Au HOHs were used as nano-carriers to assemble detection antibody (Ab2) and the PAMAM-NFLX complex. Besides, it can further enhance the ECL signal by promoting the generation of intermediate free radical HO(•) during the ECL reaction of S2O8(2-)-O2 system. The proposed immunosensor shows high sensitivity and specificity, and responds linearly to the concentration of TSH from 0.05 to 20 μIU mL(-1) with a low detection limit of 0.02 μIU mL(-1) (S/N=3). Moreover, the immunosensor successfully achieves the detection of TSH in practical human blood serum with desirable results.