A Versatile Centrifuge-Coupled Lab-on-a-Compact Disk Hardware for Quantification of Cell Volume Fractions by Electrical Impedance Spectroscopy

A versatile, centrifuge-coupled lab-on-a-compact
disk (ccLoCD) hardware is developed for high through-put
quantification of cell volume fractions (φ) by electrical impedance
spectroscopy (EIS). The eight-electrode sensor hardware consists
of 32-bit ARM microcontroller, impedance converter, and two
high-speed analog multiplexer (MUX) modules on a disk mounted
on a motor. It was evaluated by quantifying red blood cells
(RBCs) of; 1. chicken (φRBC
chic ) mixed with pork RBC with
centrifugation and 2. pork RBC (φRBC
por ) as they sediment into the
sensor in saline (S), 50% plasma (50-P) and whole blood (WB) for
assay of effects of protein concentration (Concp) on erythrocyte
sedimentation rates (ESRs). To check quantification accuracy
(QA), φRBC
por (blood hematocrit) in cardiopulmonary bypass (CPB)
was measured in comparison to φRBC
por from standard microcentrifuge
(MC) method at increasing plasma volumes (vp). Blood
impedance, measured between 10 and 100 kHz, was analyzed by
distribution of relaxation times (DRTs) and regression modeling
to quantify φ by correlating (R2) amplitude maxima (γmax) to
φ. From results at characteristic relaxation time τc = 1 ×
10−5 s, differences in γmax before and after centrifugation were
statistically significant ( p < 0.05) with centrifugation increasing
QA thus raising R2 from 0.0242 to 0.989. In 15 min, differences
in φRBC
por for RBC sedimentation in S, 50%-P, and WB were also
statistically significant ( p < 0.05) showing capacity of hardware
to capture Concp effects. In QA analysis, hardware-based φRBC
por
had low 0.73% error relative to MC-based φRBC
por . The φRBC
por
strongly correlated with vp in flow (R2 = 0.9937) which shows
hardware’s potential for low cost measurements of cell φ.