Contributed talk

Surface modifications in biometal alloys determinate cellular response

Marcus Jäger, Universität Duisburg-Essen, Essen, Germany

In elderly people, reduced cellular response to osteogenic stimuli and systemic factors increases the risk for osteoporotic fracture, prolonged bone healing or aseptic loosening of permanent orthopaedic implants. Improvements in implant design such as surface modifications as well as biomaterial coating with growth hormones or the application of mesenchymal stroma cells (MSC) may improve local bone regeneration. In the present study, we present the technique of rhBMP-2 and RGD coating on different metal alloys and its effects on the proliferation and osteogenic differentiation of human mesenchymal stem cells (MSC).

Different biometal specimen alloys with a typical endoprosthetic surface geometry (sandblasted, polished, porocoated) were coated by amination and polyethylene glycolysation with covalently immobilized, cyclic RGD molecules or were covered with PLLA/rhBMP-2. Surface properties of the biometals before cultivation were controlled by REM and profilometer. We assessed different parameters such as coating efficiency, BMP-2 release, cell proliferation, protein concentration and ALP activity.

The deposit of proteins and/or cells influence surface parameters such as Ra, Rz or contact angle significantly. The applied binding techniques were sufficient and stable in aqueous solutions to allow biocompatibility tests and also investigations on osteoblast differentiation in mesenchymal progenitor cells. Depending on the surface geometry and the coating type, cells showed a different behaviour regarding morphology, proliferation and protein expression including typical osteoblastic markers such as ALP.

The results suggest a surface structure based guidance of cellular growth, proliferation and migration. Furthermore, new laser technology applied in another study of our group demonstrated promising results to increase surface activity by nanostructures.

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