Hydroxyapatite Pellets as Versatile Model Surfaces for Systematic Adhesion Studies on Enamel: A Force Spectroscopy Case Study br

Research into materials for medical application draws inspiration from naturally occurring or synthesized surfaces,just like many other research directions. For medical application ofmaterials, particular attention has to be paid to biocompatibility,osseointegration, and bacterial adhesion behavior. To understandtheir properties and behavior, experimental studies with naturalmaterials such as teeth are strongly required. The results, however,may be highly case-dependent because natural surfaces have thedisadvantage of being subject to wide variations, for instance intheir chemical composition, structure, morphology, roughness, andporosity. A synthetic surface which mimics enamel in itsperformance with respect to bacterial adhesion and biocompatibility would, therefore, facilitate systematic studies much better.In this study, we discuss the possibility of using hydroxyapatite (HAp) pellets to simulate the surfaces of teeth and show thepossibility and limitations of using a model surface. We performed single-cell force spectroscopy with singleStaphylococcus aureuscells to measure adhesion-related parameters such as adhesion force and rupture length of cell wall proteins binding to HAp andenamel. We also examine the influence of blood plasma and saliva on the adhesion properties ofS. aureus. The results of thesemeasurements are matched to water wettability, elemental composition of the samples, and the change in the macromoleculesadsorbed over time on the surface. We found that the adhesion properties ofS. aureuswere similar on HAp and enamel samplesunder all conditions: Significant decreases in adhesion strength were found equally in the presence of saliva or blood plasma on both surfaces. We therefore conclude that HAp pellets are a good alternative for natural dental material. This is especially true when slightvariations in the physicochemical properties of the natural materials may affect the experimental series