Electrical impedance assays of blood cells

Abstract

In this review, the capability of electrical impedance spectroscopy analysis of blood cells, especially for red blood cells is presented, highlighting its large area of related biomedical relevance. The method is briefly intro- duced and basic theoretical aspects are discussed by considering both phenomenological (e.g. equivalent circuit) and microscopic approaches. The latter include a comparative analysis of the relevance of considering real shape (consistent with microscopic observations) versus spheroidal approximations (prolate and oblate spheroids) with the same surface and volume concentration. We show that while ellipsoidal approximation is fairly good for ran- domly oriented cells, it is quite poor whenever oriented cells are measured. The voluminous literature on the elec- trical analysis of blood cells is reviewed to stress the most promising biomedical applications of the method either per se or in combination with complementary e.g. (micro) fluidic approaches. Keywords: electrical impedance spectroscopy, equivalent circuit, microscopic approach, prolate and oblate spheroids, red blood cell aggregation Abbreviations: electrical impedance spectroscopy (EIS), red blood cells (RBCs), white blood cells (WBCs), red blood cell aggregation (RBCa), sample under test (SUT), geometric factor of the SUT(GESUT), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), cardiovascular diseases (CVDs), prothrombin time (PT), partial thromboplastin time (PTT), and thrombin clotting time (TCT), electric impedance microflow cytometry (EIMC), sickle cell disease (SCD), acquired immunodefi- ciency syndrome (AIDS). INTRODUCTION