Quenching of the emission of peroxydisulfate system by ferrocene functionalized chitosan nanoparticles: A sensitive “signal off” electrochemiluminescence immunosensor.

Abstract: In this paper, a novel sensitive “signal off” electrochemiluminescence (ECL) immunosensor was constructed by ferrocene functionalized chitosan nanoparticles (Fc-CsNPs) as tag for quenching peroxydisulfate system emission for the first time. Herein, CsNPs were prepared by a facile counterion complex coacervation method, and then numerous Fc and detection antibodies (Ab2) were immobilized together via covalent cross-linking. The sensing platform was constructed by assembling carboxyl polyamidoamine (PAMAM) dendrimers onto bovine serum albumin (BSA) modified electrode. Herein, BSA layer provided a multifunctional interface with good biocompatibility and sufficient active sites to produce conjugates with PAMAM. Then, PAMAM may play dual roles that not only as carriers to immobilize numerous capture antibodies but also as enhancer to significantly increase the ECL of peroxydisulfate system, thus, greatly improving the immunosensors’ sensitivity. After a sandwich-type immunoreaction, a remarkable decrease of ECL signal was observed due to the ECL quenching of peroxydisulfate by Fc-CsNPs labeled Ab2. As a result, the logarithm of change of ECL intensity has a direct relationship with the logarithm of N-terminal pro-B-type natriuretic peptide concentration in the range of 0.001–2pg/mL with a detection limit of 0.33fg/mL (S/N=3). [Copyright &y& Elsevier]