A Mechanical Device to Evaluate the Effects of Dynamic Loading in Weak-acid Medium on the Bioapatite of Devitalized Cort

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RESEARCH PAPER

A Mechanical Device to Evaluate the Effects of Dynamic Loading in Weak-acid Medium on the Bioapatite of Devitalized Cortical Bone M. Zhovner 1 & A.N. Kalinkevich 1

&

S.N. Danilchenko 1 & V.N. Kuznetsov 1 & J. Wang 2 & H. Li 2 & J. He 2 & X. Feng 2

Received: 27 November 2018 / Accepted: 11 May 2020 # The Society for Experimental Mechanics, Inc 2020

Abstract A new device that enables the application of controlled mechanical loads to devitalized cortical bone blocks in liquid media mimicking physiological environment is described. In the setup, it is possible to evaluate elimination of calcium from a bone during the exposure to slightly acidic media in the presence or absence of periodic controlled mechanical load. In the test experiments with the fragments of cortical bone, the level of calcium elimination from a bone during the experiment has shown the visible dissimilarity for the loaded bone and the unloaded one. The structural alterations in the apatite of the bone after the experiments in the setup have been studied by X-ray diffraction (XRD), which has shown that the lattice microstrain parameter of the bone mineral noticeably increases in the loaded bone compared with unloaded, while the crystallite size shows only a trend to slight increasing. This simple and easy to reproduce bone-loading setup could be used for in vitro studies of the bone material stability under mechanical loading. Keywords Bone-loading device . Weak-acid medium . Bioapatite . Calcium elimination . Lattice microstrain

Introduction Long-term stay in microgravity results in a noticeable demineralization of bone, which is a serious obstacle for long-term space expeditions [1–3]. This effect is analogous to the effect experienced by the persons on earth affected by osteoporosis [4, 5]. Furthermore, the immobilization of biological objects also leads to similar changes in bones and is often used for modeling of natural bone loss [6, 7]. On the contrary, numerous experiments in vivo have proved that loading induces bone formation, and inhibits resorption [8–11]. The detailed mechanisms of these effects are unknown so far. Some investigators suggest the essential role of mechanoelectrical (piezoelectric) properties of bone tissue (electric polarization in bone apatite crystals resulting from the application of mechanical stress) [12, 13]. Probably, the complex physiological process includes electro-mechanical triggering of cellular * A.N. Kalinkevich [email protected] 1

Institute of applied physics, NAS of Ukraine, Sumy 40000, Ukraine

2

Key Laboratory of Space Radiobiology of Gansu Province & CAS Key Laboratory of Heavy Ion Radiation Biology and Medicine, Institute of Modern Physics, Lanzhou 730000, China

chemical effects on bone apatite. On the other hand, some papers indicate that bone collagen mineralization seems to be dictated by piezoelectricity alone [12]. Under conditions of weightlessness or immobilization, a number of factors affect the bone tissue of a biological object: physical, physiological and cellula