Dynamic Viscosity of Hemoglobin Solutions Determined by Transverse Proton Magnetic Relaxation

A method based on transverse proton magnetic relaxation to determine the η_Hb is presented. The procedure is supported by the inverse relationship between η_Hb and T₂. 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) η_Hb in Hb solutions of different concentrations and in non-diluted Hb samples belonging to healthy individuals. The CPMG pulse sequence was employed to determine T₂ 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 R₂ = 1/T₂ as a function of η_Hb was obtained, making possible the evaluation of this viscosity starting from the experimental measurement of T₂. A theoretical expression was derived, which properly describes the behavior of R₂ as a function of η_Hb and supports the obtained calibration curve. The method developed, using the transverse proton magnetic relaxation, was successfully used to calculate η_Hb in samples belonging to 10 healthy individuals, and its potential utility for medical applications was observed estimating η_Hb 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 τ 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.