Mineral coatings modulate β-TCP stability and enable growth factor binding and release

beta-Tricalcium phosphate (beta-TCP) is an attractive ceramic for bone tissue repair because of its similar composition to bone mineral and its osteoconductivity. However, compared with other ceramics beta-TCP has a rapid and uncontrolled rate of degradation. In the current study beta-TCP granules were mineral coated with the aim of influencing the dissolution rate of beta-TCP, and also to use the coating as a carrier for controlled release of the growth factors recombinant human vascular endothelial growth factor (rhVEGF), modular VEGF peptide (mVEGF), and modular bone morphogenetic protein 2 peptide (mBMP2). The biomineral coatings were formed by heterogeneous nucleation in aqueous solution using simulated body fluid solutions with varying concentrations of bicarbonate (HCO3). Our results demonstrate that we could coat beta-TCP granules with mineral layers possessing different dissolution properties. The presence of a biomineral coating delays the dissolution rate of the beta-TCP granules. As the carbonate (CO32-) content in the coating was increased the dissolution rate of the coated beta-TCP also increased, but remained slower than the dissolution of uncoated beta-TCP. In addition, we showed sustained release of multiple growth factors, with release kinetics that were controllable by varying the identity of the growth factor or the CO32- content in the mineral coating. Released rhVEGF induced human umbilical vein endothelial cell (HUVEC) proliferation, and mVEGF enhanced migration of mouse embryonic endothelial cells in a scratch wound healing assay, indicating that each released growth factor was biologically active. (c) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.