Electrical impedance microflow cytometry with oxygen control for detection of sickle cells

Abstract

Polymerization of intracellular sickle hemoglobin induced by low oxygen tension has been recognized as a primary determinant of the pathophysiologic manifestations in sickle cell disease. Existing flow cytometry techniques for detection of sickle cells are typically based on fluorescence markers or cellular morphological analysis. Using microfluidics and electrical impedance spectroscopy, we develop a new, label-free flow cytometry for non-invasive measurement of single cells under controlled oxygen level. We demonstrate the capability of this new technique by determining the electrical impedance differential of normal red blood cells obtained from a healthy donor and sickle cells obtained from three sickle cell patients, under normoxic and hypoxic conditions and at three different electrical frequencies, 156kHz, 500kHz and 3MHz. Under normoxia, normal cells and sickle cells can be separated completely using electrical impedance at 156kHz and 500kHz but not at 3MHz. Sickle cells, intra-patient and inter-patient show significantly different electrical impedance between normoxia and hypoxia at all three frequencies. This study shows a proof of concept that electrical impedance signal can be used as an indicator of the disease state of a red blood cell as well as the cell sickling events in sickle cell disease. Electrical impedance-based microflow cytometry with oxygen control is a new method that can be potentially used for sickle cell disease diagnosis and monitoring.