Electrochemical sandwich immunoassay for quantification of therapeutic drugs based on the use of magnetic nanoparticles and silica nanoparticles

Adalimumab (Ada) is widely used to treat autoimmune diseases, and a correct dose of Ada can maintain therapeutic effectiveness and relieve symptoms. This study develops a rapid quantifying method of Ada using magnetic nanoparticle (MNP)-based immunoreaction and disposable screen-printed carbon electrodes (SPCEs). Anti-Ada Fab fragment and mouse anti-human antibody is respectively used as primary antibody (Ab1) and secondary antibody (Ab2). Glucose oxidase (GOD) and the Ab2 were co-immobilized on silica nanoparticles (SiNPs) with the concentration ratio of 3:1 to promise good immune affinity and the more amount of immobilized GOD. After sequentially immunoreacting Ada with Ab1@MNPs and GOD-Ab2@SiNPs, the separated GOD-Ab2@SiNPs/Ada/Ab1@MNPs complex was dripped on the glucose/ferricyanide-coated SPCEs for GOD catalysis, and then the anodic current of reduced ferrocyanide was used for the quantification of Ada. The MNP-based immunoassays have good linearity from 0.1 mu g/mL to 2 mu g/mL and a limit of detection of 15.5 ng/mL Moreover, the immunoassays can practically measure the Ada concentrations in 10-fold diluted patient serum samples with good recovery. The operation time of MNP-based immunoassays takes only about 0.5 h. The disposable MNP-based immunoassays have great promise to develop a rapid quantification platform for therapeutic drug monitoring. (C) 2019 Elsevier B.V. All rights reserved.