Pore structure engineering for carbon foams as possible bone implant material

In this study authors aim to produce carbon foams with controllable pore size and distribution with high ratio of open porosity and to determine the cytotoxicity, and the bio-compatibility of the carbon foams by controlled experiments on the Dawley rats. Carbon foams are produced from Mitsubishi AR pitch at different pressures, temperatures, pressure release times, and additives for the purpose of using it as a bone implant material. Carbon foams with controllable range of pore sizes and distribution by using temperatures between 283 and 300 degrees C, pressures between 38 and 78 bar, and pressure release times between 5 and 600 s. The highest total porosity was found to be 86%. This porosity level was also complemented by the highest density, and compressive strength. Addition of isotropic pitch, graphite powder and THF, toluene and xylene solvents resulted in higher pore volumes compared with no additives. In the case of exploiting this result, it should be noted that higher pore volumes are realized with drastic drop in porosity and strength. The ability of porous foam to provide scaffold to tissue in vivo was finally investigated after 3 months of implantation in adequate pockets in the nude mice for insertion. Histological examination of the engineered constructs revealed that the tissue adaptation and bone compatibility of the carbon foam material studies on rats was found to be satisfactory. Progression of connective tissue formation into the carbon implant was observed without any sign of cytotoxicity and incompatibility during the postoperative follow-ups. (C) 2007 Wiley Periodicals, Inc.