Magnetic Separation of Malaria-Infected Red Blood Cells in Various Developmental Stages

Abstract

Malaria is a serious disease that threatens the public health, especially in developing countries. Various methods have been developed to separate malaria-infected red blood cells (i-RBCs) from blood samples for clinical diagnosis and biological and epidemiological research. In this study, we propose a simple and label-free method for separating not only late-stage but also early-stage i-RBCs on the basis of their paramagnetic characteristics due to the malaria byproduct, hemozoin, by using a magnetic field gradient. A polydimethylsiloxane (PDMS) microfluidic channel was fabricated and integrated with a ferromagnetic wire fixed on a glass slide. To evaluate the performance of the microfluidic device containing the ferromagnetic wire, lateral displacement of NaNO2-treated RBCs, which also have paramagnetic characteristics, was observed at various flow rates. The results showed excellent agreement with theoretically predicted values. The same device was applied to separate i-RBCs. Late-stage i-RBCs (trophozoites and schizonts), which contain optically visible black dots, were separated with a recovery rate of approximately 98.3%. In addition, using an optimal flow rate, early-stage (ring-stage) i-RBCs, which had been difficult to separate because of their low paramagnetic characteristics, were successfully separated with a recovery rate of 73%. The present technique, using permanent magnets and ferromagnetic wire in a microchannel, can effectively separate i-RBCs in various developmental stages so that it could provide a potential tool for studying the invasion mechanism of the malarial parasite, as well as performing antimalarial drug assays.

Microfluidic Blood Cell Sorting: Now and Beyond

“…[87] Such strategy based on microfluidic magnetophoresis to examine paramagnetic signatures of blood cells was also recently utilized for disease diagnosis to differentiate and separate healthy RBCs from early- and late-stage malaria-infected RBCs. [88] …”

Separation of Magnetic Particles Using an Array of Magnets —A Model of a Separation Device for Malaria-Infected Blood Cells

“…One of them is a microfluidic device that is cheap, requires less diagnosis time, uses small amounts of samples, and does not need a skilled technician. (4)(5)(6)(7)(8)(9)(10) Recently, hemozoin, produced by a malaria parasite invading red blood cells, is being considered as an alternative biomarker for malaria diagnosis. Many research studies demonstrated that malaria-infected red blood cells (iRBCs) show magnetic properties distinct from those of healthy red blood cells (hRBCs), as shown in Table 1, and many groups have already utilized this difference for detecting or separating iRBCs in a label-free manner on a high gradient of a magnetic field inside the microfluidic device.…”

“…Many research studies demonstrated that malaria-infected red blood cells (iRBCs) show magnetic properties distinct from those of healthy red blood cells (hRBCs), as shown in Table 1, and many groups have already utilized this difference for detecting or separating iRBCs in a label-free manner on a high gradient of a magnetic field inside the microfluidic device. (4)(5)(6)(7)(8) However, the current design has some limitations, such as being a batch process, having low precision, or causing severe damage to iRBCs. One important issue to be resolved is the significant reduction in the magnitude of the magnetic force with distance from the magnet poles.…”

“…(4) The microfluidic channel combined with a ferromagnetic wire in a microscale, on the other hand, is difficult to operate as well as requiring a highly precise fabrication. (5) To tackle the problem, we employed an array of magnets, as an array can locally generate a high gradient of magnetic field as well as a magnetic force that are comparable to a single magnet pole. Although the magnitude of magnetic force from a single magnet is slightly higher, the capability to extend a high-force region along a microchannel using the array of magnets is necessary.…”

Electrical response of a B lymphoma cell line latently infected with Kaposi’s sarcoma herpesvirus

“…For example, Plasmodium falciparum -infected red blood cells (RBCs) showed significant differences in its cell deformation, magnetic, and electrical properties compared with uninfected RBCs(Guo et al 2012; Nam et al 2013; Soo Hoo et al 2004). Various platforms have been developed to sort infected RBCs based on their morphological changes.…”