Magnetic nanoparticles synthesized intracellularly by magnetotactic bacteria, known as “magnetosomes,” possess superior properties compared to artificially produced nano-magnets. Magnetosomes have been applied to various fields, including the development of highly sensitive immunoassays and as magnetic carriers in drug delivery systems. Furthermore, advancements in genetic engineering of magnetotactic bacteria have enabled the immobilization of foreign proteins on the surface of magnetosomes (referred to as the magnetosome display system). This innovation has facilitated the production of protein-magnetosome complexes in a simpler and more cost-effective manner. In our laboratory, we are particularly focusing on immobilizing membrane receptors—major drug targets in the field of drug discovery—onto magnetosomes, aiming to develop novel tools for pharmaceutical screening.