Abstract
Background
Calcium orthophosphates, such as hydroxyapatite (Ca5(PO4)3OH) (HA), have long been employed as bone graft materials. Recent work has suggested that calcium pyrophosphate (Ca2P2O7) (CaPy) may strongly stimulate bone deposition. In this study we compare calcium orthophosphate and pyrophosphate precipitates as suitable bone regeneration materials. As well as HA, two forms of pyrophosphate precipitate were compared in this work: amorphous calcium pyrophosphate (amCaPy) and star particle calcium pyrophosphate (stCaPy).
Methods
Briefly, 0.15M Na4P2O7·10H2O and 0.3M Ca2Cl·2H2O solutions of equivalent volume were combined and left to age before performing a series of filtration and re-suspension steps upon the precipitate. Drying yielded amCaPy powder. stAmPy was produced by the same procedure however the pH of the starting solutions were altered to pH7 before combination.
Results
We systematically investigated formulation parameters to produce powder and granular materials, which were characterised by means of XRD, mechanical testing, in vitro degradation, porosimitry, SEM. Our in vitro cellular studies have shown that CaPy exhibits greater osterogenic potential compared to HA through increased calcium deposition and alkaline phosphatase expression.
Conclusions
The development of this material is an exciting avenue for the following reasons: - Pyrophosphate is a high potential bio-ceramic - Tuneable attributes (e.g. setting, mechanical, degradation, porosity etc.) - In vivo results demonstrate CaPy has better osteogenic potential compared to HA Level of evidence amCaPy and stCaPy particulates are both being investigated as potential bone regeneration materials both in vitro and in vivo.
