Early and sensitive diagnosis of celiac autoimmune disease by using carboxylic acid functionalized magnetic nanoparticles-assisted biosensing platform

A novel impedimetric magneto-immunosensor based on iron oxide (Fe₃O₄) nanoparticles coated with 3-phosphonopropionic acid (3-PPA) (functionalized magnetic beads, or FMBs) was created for the highly sensitive and selective detection of anti-tissue transglutaminase antibody (anti-tTG) in human serum. This label-less immunosensor was introduced by magnetically attaching FMBs onto the working electrode surface with a neodium magnet. The FMBs were utilized as a sensing interface and had carboxylic acid groups for tTG molecules, which could selectively link the target anti-tTG antibody. The FMBs modification steps were carried out in microcentrifuge tubes and concentrated with magnetic force before electrochemical analyses. The specific immuno-interactions on the FMBs surface were characterized by using the electrochemical and microscopic techniques, and in the presence of anti-tTG antibodies, they were captured by tTG-immobilized magnetic beads, and significant increases were observed in impedimetric response. The magneto biosensor response was linearly related to the anti-tTG antibody level in a broad linear range of 0.125-15.62 U/mL and a low detection limit (LOD) of 0.04 U/mL. Additionally, this magneto sensor was stable, repeatable, reproducible, selective, and sensitive for determination of the anti-tTG. The commercial enzyme-linked immunosorbent assay (ELISA) method was employed to compare the responses of the suggested immunosensor in actual samples. The magneto biosensor results were in good agreement with the ELISA reference technique results. Consequently, the biosensor performance in the analysis of serum samples was acceptable.