Transforming growth factor- beta 1 incorporation in an alpha -tricalcium phosphate/dicalcium phosphate dihydrate/tetracalcium phosphate monoxide cement: release characteristics and physicochemical properties

The osteoconductive properties of calcium phosphate cements (CPCs) may be improved by the addition of growth factors, such as recombinant human transforming growth factor- beta (rhTGF- beta 1). Previously we have shown that rhTGF- beta 1 was released from cement enriched with rhTGF- beta 1 and subsequently stimulated the differentiation of pre-osteoblastic cells from adult rat long bones. It is unknown whether the addition of rhTGF- beta 1 changes the material properties of this alpha -tricalcium-phosphate ( alpha -TCP)/tetracalcium-phosphate-monoxide (TeCP) /dicalcium-phosphate-dihydrate (DCPD) cement, and what the characteristics of the release of rhTGF- beta 1 from this CPC are. Therefore, in the present study we determined the release of rhTGF- beta 1 from cement pellets in vitro. The possible intervening effects of the CPC modification for intermixing rhTGF- beta 1 on physicochemical properties were studied by assessing the compressive strength and setting time, as well as crystallinity, calcium to phosphorus ratio, porosity and microscopic structure. Most of the previously incorporated rhTGF- beta 1 in the cement pellets was released within the first 48 h. For all concentrations of rhTGF- beta 1 intermixed (100 ng-2.5 mg/g CPC), approximately 0.5% of the amount of rhTGF- beta 1 incorporated initially was released in the first 2h, increasing to 1.0% after 48 h. The release of rhTGF- beta 1 continued hereafter at a rate of about 0.1% up to 1 week, after which no additional release was found.