Open Access

Andreas Hartmann-Ferri

• Adhesion and biological interfaces were studied from two different points of view. Driven by the desire of improved implant surface materials, a novel device for implant research was developed which allows the study and dynamic analysis of cell adhesion and detachment processes, the De-Adhesion Number Investigator DANI. It makes very short measuring times accessible, enables the operator to simulate various altered physiological conditions, is very flexible in terms of implant sample material (no requirements e.g. on optical, mechanical or electrical properties) and is very cost-effective, which all states an enormous advantage compared to present-state animal tests which are often applied in clinical research. The tool is based on the well-established surface acoustic wave (SAW)-driven microfluidics technology (cf. also Hartmann et al. (2013)). Several adhesion experiments with respect to different implant samples as well as to altered physiological conditions were carried out enAdhesion and biological interfaces were studied from two different points of view. Driven by the desire of improved implant surface materials, a novel device for implant research was developed which allows the study and dynamic analysis of cell adhesion and detachment processes, the De-Adhesion Number Investigator DANI. It makes very short measuring times accessible, enables the operator to simulate various altered physiological conditions, is very flexible in terms of implant sample material (no requirements e.g. on optical, mechanical or electrical properties) and is very cost-effective, which all states an enormous advantage compared to present-state animal tests which are often applied in clinical research. The tool is based on the well-established surface acoustic wave (SAW)-driven microfluidics technology (cf. also Hartmann et al. (2013)). Several adhesion experiments with respect to different implant samples as well as to altered physiological conditions were carried out en passant serving as a proof-of-principle. Based on the initial design, further geometries of the actuators for the microfluidic flow were tested which opens a wide range of potential applications as the properties of the flow (e.g. homogeneous, inhomogeneous) can be adapted to the particular requirements of a given experiment. A quite different approach to study biological interfaces was taken by single-molecule force spectroscopy experiments using the BioForceProbe (BFP) technique (cf. Evans et al. (1995)). Here, the blood-borne protein vWF was fixed at two spots, set under a certain pre-tension and observed with respect to the force which it applies to an external force sensor. This setup was interpreted as a tube-shaped, 2-dimensional interface between the molecule and the surrounding water. Following this idea, the system was analyzed from the point of view of thermodynamics whereat a thermodynamic approach was chosen which is based on the ideas of Einstein's reversion and proper 2D entropy at interfaces. Central predictions of this approach include, that the system would undergo various fluctuations in thermodynamic observables depending on its thermodynamic state. These predictions clearly could be confirmed which opens the possibility of integration of polymer physics into the quoted thermodynamic model. Beyond that, cell adhesion experiments with altered physiological conditions were carried out with the DANI system (cf. above) which as well exhibited potential for a deeper insight of the physical foundations of cell adhesion again using the described idea of thermodynamics at interfaces. From the point of view of integration of cell adhesion into this model, these first experiments, in particular those with temperature and pH variations, showed promising results. For a more thorough foundation of this hypothesis of being able to integrate cell adhesion into this model, a crucial experiment was suggested which includes clear predictions and therefore the chance of falsification.…