Crystallinity of tissue mineral as evaluated by electron spin resonance spectometry

Crystallinity of bone mineral as well as mineral deposited in the course of pathological calcification was measured by the use of electron spin resonance (esr) spectometry in tissue samples previously irradiated with ionizing radiation. Defects caused by irradiation in the crystalline lattice of hydroxypatite crystals are paramagnetic in nature, stable and connected with the crystalline fraction of tissue mineral only. The crystallinity coefficient, defined as the ratio of these paramagnetic centers to the total ash content, changes in bone in the course of development, ageing and in pathology. The accuracy and sensitivity of esr method developed for estimation of crystallinity of tissue mineral are discussed. Examples are given for application of the esr method for the research of normal and pathologically changed mineralizing tissues. The sensitivity of the esr method permitted the measurements of crystallinity of single isolated osteons in different stages of calcification, as well as the evaluation of crystallinity of mineral deposits in subcellular fractions, e.g., calcium-loaded mitochondria. The developed technique might be applied in clinical research for diagnosis and monitoring of therapy in selected bone diseases.