NMR relaxation properties of the synthetic malaria pigment β-hematin.

200 million patients suffer from malaria, a parasitic disease caused by protozoans of the genus Plasmodium. Reliable diagnosis is crucial since it allows the early detection of the disease. The development of rapid, sensitive and low-cost diagnosis tools is an important research area. Different studies focused on the detection of hemozoin, a major by-product of hemoglobin detoxification by the parasite. Hemozoin and its synthetic analog, β-hematin, form paramagnetic crystals. A new detection method of malaria takes advantage of the paramagnetism of hemozoin through the effect that such magnetic crystals have on Nuclear Magnetic Resonance (NMR) relaxation of water protons. Indeed, magnetic microparticles cause a shortening of the relaxation times. In this work, the magnetic properties of two types of β-hematin are assessed at different temperatures and magnetic fields. The pure paramagnetism of β-hematin is confirmed. The NMR relaxation of β-hematin suspensions is also studied at different magnetic fields and for different echo-times. Our results help to identify the best conditions for β-hematin detection by NMR: T2 must be selected, at large magnetic fields and for long echo-times. However, the effect of β-hematin on relaxation does not seem large enough to achieve accurate detection of malaria without any preliminary sample preparation, as microcentrifugation.