Analysis of influence of fibrinogen concentration on blood dielectric properties by GHz electrical impedance spectroscopy

The influence of fibrinogen concentration on blood dielectric properties has been analyzed by GHz electrical impedance spectroscopy (EIS). The complex impedances of native blood and blood with various fibrinogen concentrations Z*blood,exp were measured by a coaxial sensor in the frequency range from 1 MHz to 3 GHz. The complex permittivity of native blood and blood with various fibrinogen concentrations ε*blood were extracted from the Z*blood,exp by equivalent circuit model based on the transmission line theory. The reactance Xblood,native and resistance Rsblood,native of native blood have a peak called characteristic frequency fc at around 300 MHz. At the time t = 0 min just after fibrinogen addition, the relative blood permittivity εblood decreases, conductivities σblood increases and fc shifts to higher frequency with increase of fibrinogen concentrations cfib in plasma. With increment of time, from t = 0 min to t = 12 min, εblood decreases while σblood slightly decreases to time because red blood cell (RBC) aggregation reaction. By comparing the εblood,native of native blood and blood with various cfib, the fibrinogen dissolved in plasma rises the blood permittivity. However, fibrinogen is unable to rise the blood permittivity unlimitedly because of RBC aggregation reaction.