Combined electrochemiluminescent and electrochemical immunoassay for interleukin 6 based on the use of TiO 2 mesocrystal nanoarchitectures.

A dual-responsive sandwich-type immunosensor is described for the detection of interleukin 6 (IL-6) by combining electrochemiluminescent (ECL) and electrochemical (EC) detection based on the use of two kinds of TiO2 mesocrystal nanoarchitectures. A composite was prepared from TiO2 (anatase) mesocages (AMCs) and a carboxy-terminated ionic liquid (CTIL) and then placed on a glassy carbon electrode (GCE). In the next step, the ECL probe Ru(bpy)3 (II) and antibody against IL-6 (Ab1 ) were immobilized on the GCE. Octahedral anatase TiO2 mesocrystals (OAMs) served as the matrix for immobilizing acid phosphatase (ACP) and secondary antibody (Ab2 ) labeled with horseradish peroxidase (HRP) to form a bioconjugate of type Ab2 -HRP/ACP/OAMs. It was self-assembled on the GCE by immunobinding. 1-Naphthol, which is produced in-situ on the surface of the GCE due to the hydrolysis of added 1-naphthyl phosphate by ACP, is oxidized by HRP in the presence of added H2 O2 . This results in an electrochemical signal (typically measured at 0.4 V vs. Ag/AgCl) that increases linearly in the 10 fg·mL-1 to 90 ng·mL-1 IL-6 concentration range with a detection limit of 0.32 fg·mL-1 . Secondly, the oxidation product of 1-naphthol quenches the ECL emission of Ru(bpy)3 2+ . This leads to a decrease in ECL intensity which is linear in the 10 ag·mL-1 to 90 ng·mL-1 concentration range, with a detection limit of 3.5 ag·mL-1 . The method exhibits satisfying selectivity and good reproducibility which demonstrates its potential in clinical testing and diagnosis. Graphical abstract A dual-responsive sandwich-type immunosensor was fabricated for the detection of interleukin 6 by combining electrochemiluminescence and electrochemical detection based on the use of two kinds of TiO2 mesocrystal nanoarchitectures.