Modeling and Computation of Hydroxyapatite Nanostructures and Properties

Abstract

Hydroxyapatite (Ca5(PO4)3 OH) (HAp) is a crystalline structure and composition analogue to calcified tissues of vertebrates. The biomedical significance of HAp is its bioactivity – HAp ceramics leads to the formation of new bone on their surface. HAp properties are ascribed to the characteristic surface structure of HAp, while the detailed mechanism is still unknown. Modeling and computation of HAp molecular nanostructures, exploration of the possible mechanisms of its surface charging (polarization), based on proton transfer, and the discussion of the adhesion properties of HAp nanoparticles and ceramics are the aim of the work.

Компьютерные Исследования Наноструктур Гидроксиапатита, Их Особенности И Свойства

“…There a very small surface charge (0.000033 C/m 2 ) was registered under the following poling conditions: Ep = 400 V/mm ~ 400 kV/m, Tp = 350 C, and tp = 60 min, which is two orders lower than the above values [30,43,60] and almost four orders of magnitude smaller than the values of 0.1-0.149 C/m 2 , (under similar poling condition Ep = 100 kV/m, Tp = 400 °C, tp ~ 1 hour) [12]. The latter result was obtained by thermally stimulated depolarization current (TSDC) measurements, and is comparable with other above estimations [13][14][15][28][29][30]. The result obtained in [61] is very strange, but the authors argued that a possible reason for this great discrepancy could be, the overestimated dipole polarization determined from TSDC measurements.…”

“…Naturally, HAP is a mineral form of calcium apatite with the formula Ca5(PO4)3(OH), but it is often written as Ca10(PO4)6(OH)2 to denote that the crystal unit cell comprises two molecular units. The specific feature of HAP is that the OH − ions form inner channels along the c axis with various random OH-dipoles orientations under different external conditions, which allow the transfer of protons along this axis under special conditions (such as temperature heating and applied electric field with necessary critical values) [28][29][30][31][32]35]. Usually HAP has 2 main different forms of nano-crystalline structures (in hexagonal P63/m and monoclinic P21/b space group structures) and amorphous structure.…”

“…It is also useful for creating of new HAP nanostructures having wide biomedical applications [13][14][15][16][17][18][19]. The results of these studies [7,9,11,[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] allow us to clarify possible mechanisms of structural changes and electrical properties of HAP in the bulk crystal and on the crystal surface (electrical potential, charges and polarization). And this, in turn, will allow one to improve the efficiency of HAP interactions with the living bone cells (osteoblasts, osteoclasts, etc.)…”

Simulation and Computer Study of Structures and Physical Properties of Hydroxyapatite with Various Defects

“…Hydroxyapatite (HAP) is a mineral compound from the apatite group, the basic salt of calcium and phosphoric acid (calcium phosphate) with the formula Ca 5 (OH) (PO 4 ) 3 , a widely employed multifunctional material in biomedicine, health care, biology, ecology, catalysis, and for environmental remediation [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ]. First of all, HAP is the main mineral component of mammalian hard tissues (bone and teeth).…”

“…First of all, HAP is the main mineral component of mammalian hard tissues (bone and teeth). Along with the organic component (collagen) and living bone cells (osteoclasts, osteoblasts, and osteocytes), HAP crystallizes within the gaps of stacked tropocollagen fibrils, forming and strengthening the bone structure [ 1 , 2 , 3 , 4 , 9 ]. Due to innate bioactivity and biocompatibility, HAP is a widely used material in medicine for bone and dental surgery.…”