Microstructure and Magnetic Properties of LaSrMnO Nanoparticles and Their Application to Cardiac Immunoassay

Though enzyme-linked immunosorbent assay is widely used in laboratory medicine, it has limitations due to interactions between enzymes and secondary antibodies. Here, we propose a new cardiac assay scheme for detecting troponin I antigens based on La(1– x )Sr x MnO3 ( $x=0.10$ , 0.15, and 0.25) nanoparticles (NPs). These NPs are synthesized via a modified polyol process followed by heat treatment. An increase in $x$ induces changes in crystal structure and increases both Curie temperature and saturation magnetization. The NPs with $x=0.15$ exhibit a Curie temperature close to the human body temperature. The limit of detection is found to be 0.78 ng/mL. We also confirm that LaSrMnO NPs are reusable after heating the assay plate.