Structural Optimization of Macroporous Magnesium Phosphate Scaffolds and their Cytocompatibility
Mg-phosphate ceramics have aroused growing interest as bone replacement materials due to their ability to degrade under physiological conditions. To mimic cancelous bone and to promote tissue repair mechanisms a highly macroporous structure with open cells is desired. In this study trimagnesium phosphate (farringtonite, Mg3(PO4)2) and struvite ((NH4)Mg(PO4)·6H2O) scaffolds were developed as open cell foams using the Schwarzwalder-Somers technique and optimized for pore size and mechanical performance. Polyurethane (PU) foam (20-80 ppi) was used as a template. For the optimization of the farringtonite scaffolds, ppi number of the PU foam as well as the technique that was used to remove excess slurry were varied. Sample characterization was done by SEM, XRD and compression testing. For best results were obtained using 60 ppi PU foams leading to a compressive strength of 58 kPa (90 % porosity). Farringtonite scaffolds were modified by either polymer infiltration or transformation into struvite with an ammonium phosphate solution. The pore macrostructure was retained for both of these processes and a reduction of porosity was observed. The microstructure of struvite foams was significantly altered showing larger and more facetted crystals than farringtonite. Mechanical properties substantially improved by transformation into struvite to 730 kPa (68 % porosity). Cytocompatibility was tested using osteoblasts and fibroblasts. Cell number and cell activity (WST) were tested over a period of 3 to 13 days. Farringtonite foams showed a tendency for higher cell numbers than struvite, while the WST activity was similar. Infiltration of farringtonite with PLGA approximately doubled cell number compared to pure farringtonite. In conclusion macroporous Mg-phosphate foams have been successfully produced. Compressive strength of the foams was drastically improved by optimization of pore fineness, transformation to struvite and infiltration with PLGA. The open porous structure was retained and the materials showed good cytocompatibility.
Eyup Sabri Kayali, Gultekin Goller and Ipek Akin
A. Ewald et al., "Structural Optimization of Macroporous Magnesium Phosphate Scaffolds and their Cytocompatibility", Key Engineering Materials, Vols. 493-494, pp. 813-819, 2012