Characterization of the tissue proliferated at the blood interface of carbon/ceramic composites

The present study focuses on cell adhesion/differentiation and material stability of surfaces of the three carbon/ceramic composites implanted in intra-atrial position in dogs for 1 year. Before implantation their surface was characterized by scanning electron microscopy. After harvesting, the tissue proliferated on the blood interface was examined by histology, scanning, and transmission electron microscopy, wavelength dispersive and x-ray spectrometry, electrophoretic and enzymatic characterization of glycosaminoglycans (GAGs) which were compared to endocardiac tissue as control samples. One year after implantation, the pattern of GAGs in the newly developed tissue was characterized by: 1) a constant increase of the total GAGs present on all carbon composites, 2) a significant increase of dermatan sulfate (p less than 0.05), 3) a significant increase of chondroitin sulfate (p less than 0.05), 4) a significant decrease of heparan sulfate in Group 1, whereas this GAG fraction was increased in Groups 2 and 3. Cellular surface differentiation towards endothelial-like cells occurred in places particularly in groups 1 and 3, whereas only fibrous tissue was found covering the implants in Group 2. Fibroblastic cells with dense intracellular deposits, which produced emission of Si, Ca, and C energy as well as extracellular lipidic containing inclusions were observed. The macromolecular modifications were associated with 1) the absence of endothelial lining, 2) the migration of carbon and silicon particles, and 3) the occurrence of calcifications and lipidic inclusions. These results suggest that the relative smoothness of these materials could be responsible for the development of a tissue that did not adhere to the biomaterial, indicating that cell adhesion and functional differentiation are in intimal relationship with the physical-chemical structure of the material surface.