Development of a novel method to measure macrophage migration inhibitory factor (MIF) in sera of patients with rheumatoid arthritis by combined electrochemical immunosensor

Macrophage migration inhibitory factor (MIF) has a multitude of biological activity and is associated with a number of inflammatory and immune diseases, including rheumatoid arthritis (RA). The increased serum levels of MIF in patients not only suggest this protein as a marker for disease progression, but also as a potential therapeutic target. The aim of this study is to develop a novel electrochemical method to more precisely and conveniently measure MIF in patient sera. An IgM murine monoclonal antibody (mAb) against human MIF was prepared and used in the electrochemical immunosensor, with modified gold electrode coated with compounds of gold nanoparticles, titanium dioxide nanoparticles and thionine (NGP-NTiP-Thi) followed by adsorption of anti-MIF antibodies with IgM or IgG1 isotype. The IgM immunosensor recognized MIF in a linear relationship in the range of 0.03 and 230 ng/mL with the lower limit (S/N=3) of 0.02 ng/mL. The measurement showed considerable levels of sensitivity, selectivity, stability and long-term maintenance of bioactivity, as shown by testing with serum MIF in RA patients as compared to healthy donors. The performance of the IgM immunosensor was also superior to IgG1 sensor. Thus, we have developed a novel measurement approach for serum MIF, which may have great potential in the clinic for monitoring the course of diseases associated with increased MIF.