Simon Van Bael

Ectopic bone formation by 3D porous calcium phosphate-Ti6Al4V hybrids produced by perfusion electrodeposition.

Successful clinical repair of non-healing skeletal defects requires the use of bone substitutes with robust bone inductivity and excellent biomechanical stability. Thus, three-dimensionally functionalised porous calcium phosphate-Ti6Al4V (CaP-Ti) hybrids were produced by perfusion electrodeposition, and the in vitro and in vivo biological performances were evaluated using human periosteum derived cells (hPDCs). By applying various current densities at the optimised deposition conditions, CaP coatings with sub-micrometer to nano-scale porous crystalline structures and different ion dissolution kinetics were deposited on the porous Ti6Al4V scaffolds. These distinctive physicochemical properties caused a significant impact on in vitro proliferation, osteogenic differentiation, and matrix mineralisation of hPDCs. This includes a potential role of hPDCs in mediating osteoclastogenesis for the resorption of CaP coatings, as indicated by a significant down-regulation of osteoprotegerin (OPG) gene expression and by the histological observation of abundant multi-nucleated giant cells near to the coatings. By subcutaneous implantation, the produced hybrids induced ectopic bone formation, which was highly dependent on the physicochemical properties of the CaP coating (including the Ca(2+) dissolution kinetics and coating surface topography), in a cell density-dependent manner. This study provided further insight on stem cell-CaP biomaterial interactions, and the feasibility to produced bone reparative units that are predictively osteoinductive in vivo by perfusion electrodeposition technology.

Perfusion electrodeposition of calcium phosphate on additive manufactured titanium scaffolds for bone engineering.

A perfusion electrodeposition (P-ELD) system was reported to functionalize additive manufactured Ti6Al4V scaffolds with a calcium phosphate (CaP) coating in a controlled and reproducible manner. The effects and interactions of four main process parameters - current density (I), deposition time (t), flow rate (f) and process temperature (T) - on the properties of the CaP coating were investigated. The results showed a direct relation between the parameters and the deposited CaP mass, with a significant effect for t (P=0.001) and t-f interaction (P=0.019). Computational fluid dynamic analysis showed a relatively low electrolyte velocity within the struts and a high velocity in the open areas within the P-ELD chamber, which were not influenced by a change in f. This is beneficial for promoting a controlled CaP deposition and hydrogen gas removal. Optimization studies showed that a minimum t of 6 h was needed to obtain complete coating of the scaffold regardless of I, and the thickness was increased by increasing I and t. Energy-dispersive X-ray and X-ray diffraction analysis confirmed the deposition of highly crystalline synthetic carbonated hydroxyapatite under all conditions (Ca/P ratio=1.41). High cell viability and cell-material interactions were demonstrated by in vitro culture of human periosteum derived cells on coated scaffolds. This study showed that P-ELD provides a technological tool to functionalize complex scaffold structures with a biocompatible CaP layer that has controlled and reproducible physicochemical properties suitable for bone engineering.

In vitro cell-biological performance and structural characterization of selective laser sintered and plasma surface functionalized polycaprolactone scaffolds for bone regeneration

In the present study a structural characterization and in vitro cell-biological evaluation was performed on polycaprolactone (PCL) scaffolds that were produced by the additive manufacturing technique selective laser sintering (SLS), followed by a plasma-based surface modification technique, either non-thermal oxygen plasma or double protein coating, to functionalize the PCL scaffold surfaces. In the first part of this study pore morphology by means of 2D optical microscopy, surface chemistry by means of hydrophilicity measurement and X-ray photoelectron spectroscopy, strut surface roughness by means of 3D micro-computed tomography (CT) imaging and scaffold mechanical properties by means of compression testing were evaluated before and after the surface modifications. The results showed that both surface modifications increased the PCL scaffold hydrophilicity without altering the morphological and mechanical properties. In the second part of this study the in vitro cell proliferation and differentiation of human osteoprogenitor cells, over 14 days of culture in osteogenic and growth medium were investigated. The O2 plasma modification gave rise to a significant lower in vitro cell proliferation compared to the untreated and double protein coated scaffolds. Furthermore the double protein coating increased in vitro cell metabolic activity and cell differentiation compared to the untreated and O2 plasma PCL scaffolds when OM was used.