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

• Published in: Analytical chemistry (Washington) 2013-08, Vol.85 (15), p.7316-7323
• Main Authors: Nam, Jeonghun, Huang, Hui, Lim, Hyunjung, Lim, Chaeseung, Shin, Sehyun
• Format: Article
• Language: English
• Subjects: Biochemistry; Cell Separation - instrumentation; Cell Separation - methods; Devices; Dimethylpolysiloxanes - chemistry; Epidemiology; Equipment Design; Erythrocytes; Erythrocytes - cytology; Erythrocytes - parasitology; Ferromagnetism; Flow rate; Hemeproteins - analysis; Magnetic Phenomena; Malaria; Malaria, Falciparum - parasitology; Microfluidic Analytical Techniques - instrumentation; Microfluidic Analytical Techniques - methods; Microfluidics; Organic chemicals; Parasites; Plasmodium falciparum - physiology; Recovery; Red blood cells; Time Factors; Wire
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac4012057

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.