gms | German Medical Science

Functional healing of endosteal implants poses a high challenge to the biocompatibility of the implant surface. Preclinical cell experiments on initial cell-implant-interactions highlight the relevance of fast and plane cell adhesion on the respective surface. Conventional approaches of cell visualisation like methods based on electron microscopy or on immunohistochemistry lack the option to monitor dynamic cell attributes like attachment and contact guidance and require more or less complex fixing and staining procedures with the potential risk preparation artefacts.

Aim of this study was the continuous monitoring of the cell adhesion of vital osteogenic cells on differently treated titanium model surfaces.

We used machined, lapped and polished titanium surfaces, respectively, which were subject to profilometric analysis prior to cell experiments. For one human osteogenic cell line, we established the following specific vital dyes: DiOC₆(3) (green fluorescence: mitochondria, endoplasmatic reticulum) and Syto61 (red fluorescence: nuclear region). Defined concentrations of the vital stained cells were cultivated on the respective model surfaces. Immediately after initiation of cell adhesion, the cells were continuously observed over the next 24 hrs by using Confocal Laser Scanning Microscopy (CLSM). Synchronous excitation and detection of different optical wavelengths allowed simultaneous visualisation of both vital dyes as well as the respective implant surface. A temperature-controlled microscope attachment equipped with a CO₂-insufflation system as well as the employment of specific dipping lenses enabled constant culture conditions over the whole observation period. Even after repeated laser scans, the investigated vital dyes exhibited excellent colour stability and cell compatibility and allowed a plastic visualisation of the osteoblast morphology. For both the machined and polished surface, we observed a fast cell adhesion which resulted in flat and elongated osteogenic cells, revealing a high biocompatibility of these surfaces. In contrast, the lapped surface resulted in impaired cell adhesion with a consecutive spherical osteogenic phenotype. Differences in cell adhesion dynamics and cell morphology were clearly attributable to the different surface structures.

This pilot study established a methodology that will allow continuous visualization of early cell response on solid materials and minimise preparation artefacts. The generated results allow first predictions considering implant healing.