The PEO/PBT Copolymer-Mineralized Matrix Interface In Vitro

Previous implantation experiments have investigated the interaction between a series of PEO/PBT copolymers (Polyactive®) and bone tissue, and shown the morphology of bone-bonding with several PEO/PBT ratios. However , the underlying mechanism of bonebonding r emains largely unknown . Therefore , an invitro approach was chosen to obtain more information on the event s occurring at the PEO/PBT copolymer-bone interface. Rat marrow cells were cultured on two PEO/PBT copolymer proportions: a 60/40 ratio which is known to bond with bone tissue in-vivo and a 30170 ratio which , within one year of implantation, does not bond with bone. Evaluation was performed with light microscopy , scanning , backscatter and transmission electron microscopy and X-ray microanalysis. Surface calcification of the 60/40 material was observed . Undecalcified specimens revealed a continuum between material calcification and biologically elaborated mineralized matrix. An electron-dense region was frequently observed at the interface of this material. No signs of calcification were seen within the surface of the stiffer 30/70 polymer . Mineralized matrix was found in contact with the surface of the 30/70 but the absence of a continuity was evident at all resolutions . These results indicate that reproduction of the in-vivo findings and a rapid differentiation between different PEO/PBT ratios can be accomplished in-vitro. The rat marrow system may therefore represent a controlled tool to achieve a better understanding of the events occurring at the bonePEO/PBT copolymer interface.

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