Evaluation of the dynamic viscosity in hemoglobin solutions using proton magnetic relaxation

Abstract

A Proton Magnetic Relaxation method to determine the absolute dynamic viscosity in samples of hemoglobin (Hb) solutions (η_Hb) is presented. The approach is based on the inverse relationship between this physical parameter and the transverse proton magnetic relaxation time (T₂). The Hb samples were voluntary obtained from whole blood of healthy individuals and patients, and processed by classical methods (centrifugation, decanting and freezing-thawing cycles).The Carr-Purcell-Meiboon-Gill 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 theoretical expression was derived; which properly describes the experimental behavior of the transverse proton magnetic relaxation rate (R₂) with η_Hb. This equation was successfully used to estimate η_Hb in samples belonging to 10 healthy individuals considering that the values obtained statistically match with those measured using an Ostwald viscometer. The potential utility, for medical applications, of this proton magnetic resonance based method was observed estimating η_Hb in samples belonging to 46 sickle cell disease patients; being the estimated values bigger than those obtained for the case of healthy individuals due to the increasing in the intermolecular interactions inside the hemoglobin S solution, which is provoked by the presence of HbS polymers and fragments of this type of polymers. To use this method a special care must be taken with the temperature and the frequency of resonance used, as well as with the homogeneity of the static magnetic system. Additionally; the presence inside the sample of external amount of water, paramagnetic compounds and/or other biological materials must be avoided.