Visualising phase change in a brushite-based calcium phosphate ceramic

Abstract

The resorption of brushite-based bone cements has been shown to be highly unpredictable, with strong dependence on a number of conditions. One of the major factors is phase transformation, with change to more stable phases such as hydroxyapatite affecting the rate of resorption. Despite its importance, the analysis of phase transformation has been largely undertaken using methods that only detect crystalline composition and give no information on the spatial distribution of the phases. In this study confocal Raman microscopy was used to map cross-sections of brushite cylinders aged in Phosphate Buffered Saline, Foetal Bovine Serum, Dulbecco’s – Minimum Essential Medium (with and without serum). Image maps showed the importance of ageing medium on the phase composition throughout the ceramic structure. When aged without serum, there was dissolution of the brushite phase concomitant to the deposition of octacalcium phosphate (OCP) around the periphery of the sample. The deposition of OCP was detectable within five days and reduced the rate of brushite dissolution from the material. The use of serum, even at a concentration of 10vol% prevented phase transformation. This paper demonstrates the value of confocal Raman microscopy in monitoring phase change in biocements; it also demonstrates the problems with assessing material degradation in non-serum containing media.

In situ syntheses of hydroxyapatite‐grafted graphene oxide composites

“…The weak band at 1003 cm −1 observed in the B (Figure b, red line) and C syntheses (Figure b, blue line) corresponds to the monohydrogen phosphate (HPO 4 2− ) and it can be due to the type of reagents used for the different syntheses (disodium hydrogen phosphate for Synthesis B and diammonium hydrogen phosphate for Synthesis C) or also due to the presence of other calcium phosphate subproducts such as octacalcium phosphate (OCP; Bannerman, Williams, Cox, & Grover, ).…”

A cohesive premixed monetite biocement

“…Perhaps because HA compositionally resembles the mineral component of bone, the majority of CPC research initially focused on the formulation and refinement of HA‐based cements. Researchers have, however, demonstrated that highly crystalline HA is poorly soluble in physiological conditions and is therefore only resorbed by osteoclastic activity . This means HA cements can remain in vivo for a considerable period of time following implantation, posing a risk of catastrophic brittle failure .…”

“…Researchers have, however, demonstrated that highly crystalline HA is poorly soluble in physiological conditions and is therefore only resorbed by osteoclastic activity. [13][14][15] This means HA cements can remain in vivo for a considerable period of time following implantation, posing a risk of catastrophic brittle failure. 2 More soluble apatites, however, can be produced by reducing crystal size or crystallinity and incorporating substitutions (eg Mg 2+ , CO 3 2À ) into the apatite lattice.…”

Preparation of fibrous hydroxyapatite particles by homogeneous precipitation and microwave-assisted hydrothermal heating

“…The results are shown in FIGURE 2, as a function of (NH 2 ) 2 CO concentration. When the (NH 2 ) 2 CO concentrations were 0.04 and 0.08 mol•dm 3 , CaHPO 4 and OCP Relating to the formations of CaHPO 4 and OCP, the former compound is stable for pH < 4 25 . On the other hand, the latter compound is favored as a metastable phase in the range of pH ≃ 4 to pH ≃ 6.5, although the non-stoichiometric HAp (i.e.,Ca 10x (HPO 4 ) x (PO 4 ) 6-x (OH) 2x ) is also thermosdynamically stable for pH > 4 25 .…”