Bioceramics Based on β-Calcium Pyrophosphate

Abstract

Ceramic samples based on β-calcium pyrophosphate β-Ca2P2O7 were prepared from powders of γ-calcium pyrophosphate γ-Ca2P2O7 with preset molar ratios Ca/P = 1, 0.975 and 0.95 using firing at 900, 1000, and 1100 °C. Calcium lactate pentahydrate Ca(C3H5O3)2⋅5H2O and monocalcium phosphate monohydrate Ca(H2PO4)2⋅H2O were treated in an aqua medium in mechanical activation conditions to prepare powder mixtures with preset molar ratios Ca/P containing calcium hydrophosphates with Ca/P = 1 (precursors of calcium pyrophosphate Ca2P2O7). These powder mixtures containing calcium hydrophosphates with Ca/P = 1 and non-reacted starting salts were heat-treated at 600 °C after drying and disaggregation in acetone. Phase composition of all powder mixtures after heat treatment at 600 °C was presented by γ-calcium pyrophosphate γ-Ca2P2O7 according to the XRD data. The addition of more excess of monocalcium phosphate monohydrate Ca(H2PO4)2·H2O (with appropriate molar ratio of Ca/P = 1) to the mixture of starting components resulted in lower dimensions of γ-calcium pyrophosphate (γ-Ca2P2O7) individual particles. The grain size of ceramics increased both with the growth in firing temperature and with decreasing molar ratio Ca/P of powder mixtures. Calcium polyphosphate (t melt = 984 °C), formed from monocalcium phosphate monohydrate Ca(H2PO4)2⋅H2O, acted similar to a liquid phase sintering additive. It was confirmed by tests in vitro that prepared ceramic materials with preset molar ratios Ca/P = 1, 0.975, and 0.95 and phase composition presented by β-calcium pyrophosphate β-Ca2P2O7 were biocompatible and could maintain bone cells proliferation.

Materials in the Na2O–CaO–SiO2–P2O5 System for Medical Applications

“…The calcium pyrophosphate (CPP, Ca 2 P 2 O 7 ) ceramic is an attractive and prospective object for investigation due to the molar ratio Ca/P = 1 and values of pH close to neutral (pH ~7) during immersion in water [120], which were confirmed by dynamic studies in this direction [120][121][122][123][124][125][126][127].…”

“…The CPP has several polymorphs [70]: amorphous-CPP, which is formed at 240-450 • C; γ-CPP, which is formed at ≈ 530 • C; β-CPP, which is formed at 700-750 • C; and β-CPP, which is transformed into α-CPP at 1140-1179 • C. According to the literature, most research was dedicated to the investigation of amorphous-CPP [122,123], γ-CPP [121], and β-CPP [120,125,126], which are produced by thermal conversion of hydrated ortho-or pyrophosphate calcium [122,123], solid phase synthesis [128], and the firing of brushite cement stone/powders [120,127,129] or monetite [125].…”

Powders Based on Ca2P2O7-CaCO3-H2O System as Model Objects for the Development of Bioceramics

“…Despite the fact that significant research interest is focused on the synthesis of hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 , Ca/P = 1.67) [1,2] and calcium orthophosphate (Ca 3 (PO 4 ) 2 , Ca/P = 1.5) [3,4] phases occurring naturally in bone tissue, special attention is paid to calcium phosphates with a Ca/P molar ratio different from the that of natural inorganic bone constituents. For instance, calcium metaphosphate [5], brushite [6,7], calcium polyphosphate [8], calcium pyrophosphate (Ca 2 P 2 O 7 , CPP) [9,10], as well as their biphasic composites [11] and ion-substituted analogs [12] are widely described in the literature. It is also noteworthy that such calcium phosphate materials can act not only as independent ceramic bases for the fabrication of bone implants but also as bioactive ceramic inclusions in bioglass- [13] or polymer-based systems that are currently being studied as promising materials for cell culturing and drug delivery in the field of bioscaffolding [14,15].…”

Ceramics Based on Sodium Rhenanite CaNaPO4, Obtained via Firing of Composite Cement-Salt Stone

“…The traditionally used hydroxyapatite (HA), Ca 10 (PO 4 ) 6 (OH) 2 , has the lowest solubility among calcium phosphates [3]. In the case of a regenerative approach to the treatment of bone tissue, bioresorbable phases are introduced into the composition of materials for bone implants which, compared to HA, have greater resorption, namely tricalcium phosphate β-Ca 3 (PO 4 ) 2 (Ca/P = 1.5) [4][5][6], calcium pyrophosphate Ca 2 P 2 O 7 (Ca/P = 1) [7][8][9], tromelite Ca 4 P 6 O 19 (Ca/P = 0.66) [10,11], calcium polyphosphate Ca(PO 3 ) 2 (Ca/P = 0.5) [12], Na-substituted tricalcium phosphate Ca 10 Na(PO 4 ) 7 , K-substituted tricalcium phosphate Ca 10 K(PO 4 ) 7 , sodium rhenanite CaNaPO 4 , and potassium rhenanite CaKPO 4 [13,14]. A necessary element of any strategy for improving the solubility of a compound with an ionic nature of the chemical bond is lowering the energy of the crystal lattice.…”