Textural characteristics of model and natural bone tissues and interfacial behavior of bound water

Abstract

Water, as a probe liquid bound in model systems (highly disperse hydroxyapatite – protein composites as a model of the main components of bones) and rat bone tissues healthy and affected by osteoporosis occurred due to experimental Alzheimer’s disease (EAD), has been investigated using low-temperature 1H NMR spectroscopy, NMR cryoporometry, TG/DTG/DTA, DSC, and TG and DSC thermoporometry. The textural characteristics of these intact systems cannot be studied using the standard adsorption methods, but the cryoporometry and thermoporometry methods give these characteristics. The 1H NMR spectra of water bound in model and natural bone tissues include signals, which can be assigned to strongly associated (typical) water (SAW, chemical shift of proton resonance δH=5–6ppm) and weakly associated (atypical) water (WAW) at δH=1–2ppm. Contributions of SAW and WAW give information on textural organization of both model and natural bones. The influence of such co-adsorbates as HCl, CDCl3, CD3CN, C6D6, and (CD3)2SO on the interfacial behavior and clustering of bound water depends on their polarity, amounts of components, and textural and structural features of the materials analyzed with the 1H NMR spectroscopy and cryoporometry methods. According to the NMR cryoporometry data, the EAD causes an increase in nanoporosity of the bone tissues. The total porosity and the specific surface area of biostructures (accessible for water molecules and estimated using NMR cryoporometry and TG thermoporometry methods with a model of cylindrical pores) are larger for the EAD sample. Weakly polar chloroform-d has a significant influence on the organization of water in the bone tissue, and this effect is greater for the EAD sample as more porous material.