The influence of hemoglobin and ion interactions on the electrical conductivity of hemoglobin solutions

The electrical properties of hemoglobin (Hb) solutions are essential characteristics that offer valuable insights into red blood cell (RBC) health metrics. These properties are influenced by factors such as intracellular ions and Hb. This study uses electrical impedance spectroscopy to analyze Hb solutions prepared from both lyophilized and freshly extracted human Hb across frequency range (40 Hz to 110 MHz), aiming to clarify Hb-ion interactions and their effects on solution conductivity across physiological conditions. To determine the contributions of ions, Hb, and the measurement system to the measured impedance, electrical circuit models combined with finite element analysis in COMSOL Multiphysics, were used and validated with impedance measurements on deionized water and ionic buffer solutions of defined composition. In low ionic strength buffers (sub physiological levels), Hb addition increased conductivity of solutions, whereas in high ionic strength solutions, Hb addition altered conductivity of solutions, with these effects varying by ionic strength. Notably, at physiological ionic strengths, the addition of Hb consistently reduces the conductivity of the solution, indicating significant Hb-ion interactions that modulate the overall electrical behavior. The combined experimental and computational approach provides a robust framework for assessing the influence of Hb and ions on solution conductivity and can be extended to study other Hb variants beyond normal Hb.