Dynamic Viscosity of Hemoglobin Solutions Determined by Transverse Proton Magnetic Relaxation

A method based on transverse proton magnetic relaxation to determine the <i>η_Hb</i> is presented. The procedure is supported by the inverse relationship between <i>η_Hb</i> and <i>T</i>₂. The Hb samples were obtained starting from whole blood of healthy individuals and patients, which was processed by classical methods (centrifugation, decanting and freezing-thawing cycles). An Ostwald's viscometer was used to measure (293 K) <i>η_Hb</i> in Hb solutions of different concentrations and in non-diluted Hb samples belonging to healthy individuals. The CPMG pulse sequence was employed to determine <i>T₂</i> in a Tecmag Magnetic Resonance console coupled to a magnet of 0.095 T, and the temperature of measurement was 293 K. A calibration curve of <i>R</i>₂ = <i>1/T</i>₂ as a function of <i>η_Hb</i> was obtained, making possible the evaluation of this viscosity starting from the experimental measurement of <i>T</i>₂. A theoretical expression was derived, which properly describes the behavior of <i>R₂</i> as a function of <i>η_Hb</i> and supports the obtained calibration curve. The method developed, using the transverse proton magnetic relaxation, was successfully used to calculate <i>η_Hb</i> in samples belonging to 10 healthy individuals, and its potential utility for medical applications was observed estimating <i>η_Hb</i> in samples belonging to 46 sickle cell disease patients. To use this method a special care must be taken with the temperature, the value of <i>τ</i> and the homogeneity of the static magnetic system. Additionally, the presence inside the sample of an external amount of water, paramagnetic compounds, and/or other biological materials must be avoided.