Magnetic Rotation of Monosodium Urate and Urinary Tract Stones for Clinical Treatment Applications

In recent years, diseases such as gout and urinary tract calculi, caused by crystals in vivo, are rapidly increasing due to excess intake of alcohol, salt, and so forth. Crystals causing gout are compounds of uric acid with sodium in the blood, which are called monosodium urate (MSU) crystals. On the other hand, urinary tract calculus is caused by calcium oxalate crystal. In this paper, we focused on the behaviors of MSU crystals and oxalic acid crystals under magnetic fields of several hundreds of mT (Tesla), and developed a method for new medical treatments by using a magnetic field. MSU crystals and oxalic acid crystals were prepared by a recrystallization from the aqueous solution. We observed these crystals using a charge-coupled device microscope under horizontal magnetic fields (maximum of 500 mT). While the magnetic fields were applied, the MSU crystals were oriented by the magnetic fields. In addition, oxalic acid crystals were oriented perpendicularly to the magnetic field. The dynamic rotation of MSU crystal was observed quantitatively by measuring the time course of the lightscattering intensities of the MSU suspension. The results show that the diamagnetic anisotropy in the MSU crystals controlled the rotational responses. As a possible medical application, a remote control of the MSU crystals and oxalic acid crystals in living body by the magnetic fields is proposed.