A Novel Approach to Interpretation of the Time-Dependent Self-Diffusion Coefficient: Water-Mouse RBCs Suspension Study

Abstract

Red Blood Cells (RBCs) are ideally suited as a model system for study of water diffusion in biological tissue. We used a pulsed-field-gradient nuclear magnetic resonance technique to measure the time-dependent self-diffusion coefficient D(t) in water-mouse RBC suspension at different diffusion times. A new method of interpretation of the experimental time dependence of the self-diffusion coefficient D(t) for fluid in heterogeneous media is proposed, and this study presents a new approximation describing water diffusion in such system. Three types of water were determined, which differs according to the self-diffusion coefficients: bulk water, extracellular and intracellular water. The water molecular exchange process among these three water states was investigated. The residence time for mice RBCs was obtained. Intracellular and extracellular water self-diffusion was restricted, and the sizes of restriction regions were 1.95 μm and 6.73 μm with S/V ratio 1.534 μm⁻¹ and 0.44 μm⁻¹, respectively. The cell wall permeability determined from the resident time as 4.7·10⁻⁵ m/s agreed with the permeability 5.4·10⁻⁵ m/s obtained from time dependence of intracellular water self-diffusion coefficient.