Detection and quantification of subtle changes in red blood cell density using a cell phone

Abstract

Magnetic levitation has emerged as a technique that offers the ability to differentiate between cells with different densities. We have developed a magnetic levitation system for this purpose that distinguishes not only different cell types but also density differences in cells of the same type. This small-scale system suspends cells in a paramagnetic medium in a capillary placed between two rare earth magnets, and cells levitate to an equilibrium position determined solely by their density. Uniform reference beads of known density are used in conjunction with the cells as a means to quantify their levitation positions. In one implementation images of the levitating cells are acquired with a microscope, but here we also introduce a cell phone-based device that integrates the magnets, capillary, and a lens into a compact and portable unit that acquires images with the phone's camera. To demonstrate the effectiveness of magnetic levitation in cell density analysis we carried out levitation experiments using red blood cells with artificially altered densities, and also levitated those from donors. We observed that we can distinguish red blood cells of an anemic donor from those that are healthy. Since a plethora of disease states are characterized by changes in cell density magnetic cell levitation promises to be an effective tool in identifying and analyzing pathologic states. Furthermore, the low cost, portability, and ease of use of the cell phone-based system may potentially lead to its deployment in low-resource environments.

Detection of membrane-bound and soluble antigens by magnetic levitation

“…10 In a given setup, objects with negligible magnetic properties will rest at a levitation height that will depend exclusively on the object density. The levitation height of a complex of two beads with different densities will depend on their resulting average density.…”

“…We used an Olympus Provis AX-70 microscope mounted on the side as previously described 10 , also depicted in Fig. 1.A, to capture images in side-view of the capillary tube.…”

“…We have previously described a magnetic levitation-based and smartphone-adapted technique that measures the specific mass and density of individual red blood cells (RBCs) by reporting the levitation height of cells as compared to a set of density reference beads 10 . We used the method for rapid separation and identification of old, new, iron-deficient, and sickled red blood cells.…”

“…The signal measured in our initial approach was generated by a change in the levitation height of cells that was indicative either of their activation status, in case of neutrophils, hemoglobin or water content in the case of red blood cells, or density in the case of circulating tumor cells. 10–12 …”

A Novel Implementation of Magnetic Levitation to Quantify Leukocyte Size, Morphology, and Magnetic Properties to Identify Patients With Sepsis

“…Magnetic levitation is a relatively new technique that uses a uniform magnetic field to measure and separate cells based on their density, and magnetic properties. (9)(10)(11)(12). While the magnetic levitation technology offers a variety of opportunities for functional interrogation of cells, for this specific study, we use it as a tool to: a) isolate leukocytes from circulating red blood cells (RBCs), b) visualize leukocytes, and c) measure size, shape, density and paramagnetic property parameters of leukocytes.…”