A transmission electron microscopy examination of the interface between osteoblasts and metal biomaterials

Transmission electron microscopy was used to examine the interface between metal implant materials and bone cells. Specifically, neonatal rat calvaria osteoblasts were cultured on CoCrMo alloy and on 316L stainless steel discs (mechanically polished to a 0.3 micron finish) in Dulbecco's Modified Eagle Medium (supplemented with 10% fetal bovine serum, 50 micrograms/mL ascorbic acid, and 10 mM beta-glycerophosphate) under standard, sterile, cell culture conditions for 14 to 28 days. At the end of the prescribed time periods, the cells were fixed and embedded in resin before removing the metal substrates using an electrolytic dissolution technique and a 7% NaCl solution. Transmission electron microscopic examination of stained, ultrathin sections of the biological samples revealed an intact interface with microscopic details characteristic to the cell line and similar to those reported in the literature for animal and explant studies. The osteoblasts exhibited continuous contact and intimate apposition to both the CoCrMo and stainless steel substrate surfaces and grew in multilayered structures; an electron dense layer (composed of mucopolysaccharides and proteins) was observed at the surface of both substrates; collagen fibrils and mineralized foci were observed in the extracellular matrix interspersed among the multilayered osteoblasts.