Polishing and coating carbon fiber-reinforced carbon composites with a carbon-titanium layer enhances adhesion and growth of osteoblast-like MG63 cells and vascular smooth muscle cells in vitro

Carbon fiber-reinforced carbon composites (CFRC) are considered to be promi sing materials for orthopedic and dental surgery. Their mechanical properti es can be tailored to be similar to those of bone, and their chemical compo sition (close to pure carbon) promises that they will be tolerated well by the surrounding tissue. In this study, CFRC composites were fabricated from phenolic resin and unidirectionally oriented Torayca carbon fibers by carb onization (1000 degreesC) and graphitization (2500 degreesC). The material then was cut with a diamond saw into sheets of 8 x 10 x 3 mm, and the upper surface was polished by colloidal SiO2 and/or covered with a carbon-titani um (C:Ti) layer (3.3 mum) using the plasma-enhanced physical vapor depositi on method. Three different kinds of modified samples were prepared: polishe d only, covered only, and polished + covered. Untreated samples served as a control. The surface roughness of these samples, measured by a Talysurf pr ofilometer, decreased significantly after polishing but usually did not dec rease after coating with a C:Ti layer. On all three modified surfaces, huma n osteoblast-like cells of the MG63 line and rat vascular smooth muscle cel ls (both cultured in a Dulbecco's minimum essential medium with 10% fetal b ovine serum) adhered at higher numbers (by 21-87% on day 1 after seeding) a nd exhibited a shorter population doubling time (by 13-40%). On day 4 after seeding, these cells attained higher population densities (by 61-378%), vo lume (by 18-37%), and protein content (by 16-120%). These results were more pronounced in VSMC than in MG63 cells and in both groups of C:Ti-covered s amples than in the polished only samples. The release of carbon particles f rom the CFRC composites was significantly decreased-by 8 times in the polis hed only, 24 times in the covered only, and 42 times in the polished + cove red samples. These results show that both polishing and carbon-titanium cov ering significantly improve the biocompatibility of CFRC composites in vitr o, especially when these two modifications are combined. (C) 2000 John Wile y & Sons, Inc.