Portable Cell Tracking Velocimetry for Quantification of Intracellular Fe Concentration of Blood Cells

Hematological analysis is crucial for diagnosing and monitoring blood-related disorders. Nevertheless, conventional hematology analyzers remain confined to laboratory settings due to their high cost, substantial space requirements, and maintenance needs. Herein, we present a portable cell tracking velocimetry (CTV) device for the precise measurement of the magnetic susceptibility of biological entities at the single-cell level, focusing on red blood cells (RBCs) in this work. The system integrates a microfluidic channel positioned between permanent magnets that generate a well-defined magnetic field gradient (191.82 TA/mm²). When the cells are injected into the chamber, their particular response to the magnetic field is recorded and used to estimate their properties and quantify their intracellular hemoglobin (Hb) concentration. We successfully track over 400 RBCs per condition using imaging and trajectory analysis, enabling detailed characterizations of their physical and magnetic properties. A comparison of the mean corpuscular hemoglobin measurements revealed a strong correlation between our CTV system and standard ultraviolet-visible (UV-Vis) spectrophotometry (23.1 ± 5.8 pg vs. 22.4 ± 3.9 pg, p > 0.05), validating the accuracy of our measurements. The system's single-cell resolution reveals population distributions unobtainable through conventional bulk analysis methods. Thus, this portable CTV technology provides a rapid, label-free approach for magnetic cell characterization, offering new possibilities for point-of-care hematological analysis and field-based research applications.