Monetite vs. Brushite: Different Influences on Bone Cell Response Modulated by Strontium Functionalization

Abstract

Monetite and brushite are regarded with increasing interest for the preparation of biomaterials for applications in the musculoskeletal system. Herein, we investigated the influence of strontium substitution in the structures of these two phosphates on bone cell response. To achieve this aim, co-cultures of human primary osteoclasts and human osteoblast-like MG63 cells were tested on strontium-substituted monetite and strontium-substituted brushite, as well as on monetite and brushite, as controls. In both structures, strontium substitution for calcium amounted to about 6 at% and provoked enlargement of the cell parameters and morphologic variations. Cumulative release in physiological solution increased linearly over time and was greater from brushite (up to about 160 and 560 mg/L at 14 days for Sr and Ca, respectively) than from monetite (up to about 90 and 250 mg/L at 14 days for Sr and Ca, respectively). The increasing viability of osteoblast-like cells over time, with the different expression level of some typical bone markers, indicates a more pronounced trigger toward osteoblast differentiation and osteoclast inhibition by brushite materials. In particular, the inhibition of cathepsin K and tartrate-resistant acid phosphatase at the gene and morphological levels suggests strontium-substituted brushite can be applied in diseases characterized by excessive bone resorption.

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

“…The curve related to the CC sample (CaCO 3 ) reflects the decomposition processes of the byproduct (CH 3 COONH 4 ) and target product (Equation ( 6)). CPP-curve (Ca 2 P 2 O 7 ) reflects the processes of probable by-product decomposition, dehydration of Ca 2 P 2 O 7 •xH 2 O, and its conversion to β-Ca 2 P 2 O 7 in accordance with the reaction (7). The curve for CPP/CC sample (Ca 2 P 2 O 7 /CaCO 3 ) reflects the continuous mass loss associated with both the processes of Ca 2 P 2 O 7 •xH 2 O dehydration and chemical interaction of the charge components resulting in Ca 3 (PO 4 ) 2 formation according to the reactions ( 5) and (8).…”

“…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].…”

Microporous Ceramics Based on β-Tricalcium Phosphate

“…It was shown that thermal conversion of brushite CaHPO 4 •2H 2 O to monetite CaHPO 4 might begin at this temperature [60]. This temperature was marked as a factor that makes formation of monetite CaHPO 4 more preferable than the formation of brushite CaHPO 4 •2H 2 O during solution synthesis [23,58]. Probably, the presence of some quantity of monetite crystals as the nucleus for a more stable phase could accelerate the transformation.…”

“…HPO4‧2H2O during solution synthesis [23,58]. Probably, the presence of som monetite crystals as the nucleus for a more stable phase could accelerate mation.…”

“…There are several calcium phosphate salts with the molar ratio Ca/P = 1. These are calcium pyrophosphate Ca 2 P 2 O 7 , monetite CaHPO 4 [21][22][23], brushite CaHPO 4 •2H 2 O [24], and hydrated calcium pyrophosphate Ca 2 P 2 O 7 •xH2O [25] 4 . So, all of these calcium phosphates can be treated as precursors of calcium pyrophosphate Ca 2 P 2 O 7 .…”