An ON-OFF Magneto-Optical Probe of Anisotropic Biofluid Crystals: A β-Hematin Case Study

We have designed, developed, and evaluated an innovative portable magneto-optical detector (MOD) in which a light beam with variable polarization passes through a fluid sample immersed in a variable magnetic field. The light intensity is measured downstream along the forward scattering direction. The field is turned on and off through the in-and-out motion of nearby permanent magnets. As a result, for sufficiently, magnetically, and optically anisotropic samples, the optical absorption is sensitive to changes in the light polarization. Both detection and characterization applications are, therefore, available. For instance, both the degree of malaria infection and hemozoin crystalline properties can be measured and studied, respectively. We present experimental results for synthetic hemozoin and describe them in terms of the basic physics and chemistry underlying the correlations of the directions of the external magnetic field and the light beam polarization. We connect this work to a commercialized product for malaria detection and compare it with other magneto-optical instruments and methods. We conduct tests of absorption parameters and the electric polarizability tensor, and we discuss the connection to magnetic and electric dipole moments.