Ultrastructure of the interface between cultured osteoblasts and surface-modified polymer substrates.
Osteoblasts derived from rat bone marrow cells were cultured on surface-modified poly(ethylene terephthalate) films in the presence of ascorbic acid, beta-glycerophosphate, and dexamethasone. The surfaces employed for cell culture included the untreated hydrophobic surface and three modified surfaces possessing immobilized phosphate polymer chains, collagen molecules, and a thin hydroxyapatite-deposited layer. They all were produced by photo-induced graft polymerization with subsequent surface modifications of the graft chains. The ultrastructural morphology of the substrate/cell interfaces formed in in vitro osteoblast culture on these substrates was studied by transmission electron microscopy. The osteoblasts cultured for 1 week on the modified surfaces showed rough endoplasmic reticula rich in intracellular space and early matrix production in the extracellular space, irrespective of the surface chemistry. After 2 weeks of culture, osteoblasts exhibited active elaboration of extracellular matrix proteins, mostly composed of collagen, on all the surfaces. A remarkable result observed at this stage was direct deposition of an electron-dense, afibrillar layer of 180 nm thickness onto the surface having phosphate polymer chains. This layer became much more electron dense after 3 weeks of culture. Energy dispersive X-ray microanalysis revealed the presence of calcium phosphate in this layer. It was further found that the predeposited hydroxyapatite layer on the phosphate polymer-grafted surface promoted mineral deposition in the extracellular matrix that surrounded cuboid, osteocyte-like cells.
Yamamoto
M
M
Research Center for Biomedical Engineering, Kyoto University, Japan.
Kato
K
K
Ikada
Y
Y
D000818:Animals; D001672:Biocompatible Materials; D002454:Cell Differentiation; D002478:Cells, Cultured; D003094:Collagen; D017886:Durapatite; D004577:Electron Probe Microanalysis; D018870:Endoplasmic Reticulum, Rough / Q000648:ultrastructure; D005109:Extracellular Matrix / Q000648:ultrastructure; D008422:Materials Testing; D008854:Microscopy, Electron; D010006:Osteoblasts / Q000648:ultrastructure*; D011093:Polyethylene Terephthalates; D051381:Rats; D013499:Surface Properties
D001672:Biocompatible Materials; D011093:Polyethylene Terephthalates; D003094:Collagen; D017886:Durapatite