Magnetic Levitation is a powerful tool capable of distinguishing micron-scale particles based on their densities. When a particle is suspended in a paramagnetic medium and placed in a magnetic field formed by two permanent magnets with like poles facing each other, the particle will experience two forces, a magnetic force and a buoyancy force, which cause a particle to levitate at a height inversely proportional to its density. Magnetic Levitation has been shown to be useful for a range of applications, including disease diagnostics, material characterization, and quality control. We have developed three different versions of this technology: (A) microscopy-compatible, (B) smartphone-compatible, and (C) self-contained.
(A) It is powerful, because it allows real-time and high resolution interrogation and monitoring of cell populations or single cells. A wide variety of cellular processes, both physiological and pathological, are accompanied by transient or permanent changes in a cell’s fundamental characteristics (i) volumetric mass density or (ii) magnetic signature due to formation or quenching of intracellular paramagnetic reactive species such as, reactive oxygen species (ROS) and reactive nitrogen species (RNS). These events include cell-cycle stage, differentiation, cell-death (apoptosis/necrosis), malignancy, disease state, activation, phagocytosis, in vivo and ex vivo cell aging (e.g., red blood cells), viral infection, and specific as well as non-specific responses to drugs. Therefore, reliable cell biology tools designed for high spatial resolution, real-time monitoring and quantification of magnetic signatures and volumetric mass densities of cells will help elucidate the intricate cellular mechanisms.
(B) Simplicity, small size-scale and flexibility of the design make the system compatible with mobile devices for telemedicine and use in resource poor settings for screening and diagnostics of sickle cells and malaria-infected red blood cells. This strategy does not require antibodies, advanced microscopy instrumentation or techniques for reliable diagnosis, nor the presence of microscopy specialists. We have recently demonstrated the applicability of this approach to provide a quantitative diagnosis of sickle cell disease by developing a smartphone-compatible version of this technology and validating it among 11 SS patients. In low-resource settings such as sub-Saharan Africa (where the disease is common but no ubiquitous testing and monitoring procedures are in place), this technology can enable simple, rapid, and accessible sickle cell disease diagnostics and monitoring.
(C) We have recently developed a portable, self-contained device fully independent from a dedicated microscope or smartphone to levitate particles of interest, image them using an embedded low-cost optical system and a camera module, and process the captured images in order to estimate the densities of the particles. The device is user-friendly and inexpensive, offering a great potential for rapid, on-site sample analysis such as white blood cell cytometry and sickle cell disease diagnosis.
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