Dynamic Viscosity of Hemoglobin Solutions Determined by Transverse Proton Magnetic Relaxation.

A method based on transverse proton magnetic relaxation to determine the ηHb is presented. The procedure is supported by the inverse relationship between ηHb 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) ηHb 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 ηHb 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 ηHb and supports the obtained calibration curve. The method developed, using the transverse proton magnetic relaxation, was successfully used to calculate ηHb in samples belonging to 10 healthy individuals, and its potential utility for medical applications was observed estimating ηHb 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.