Bacterial adhesion to dental implants is the onset for the development of pathological biofilms. Reliable characterization of this initial process is the basis towards the development of anti-biofilm strategies. In the present study, single-cell force spectroscopy (SCFS), by means of an atomic force microscope connected to a microfluidic pressure control system (FluidFM), was used to comparably measure adhesion forces of different oral bacteria within a similar experimental setup to the common implant material titanium. The bacteria selected belong to different ecological niches in oral biofilms: the commensal pioneers Streptococcus oralis and Actinomyces naeslundii; secondary colonizer Veillonella dispar; and the late colonizing pathogens Porphyromonas gingivalis as well as fimbriated and non-fimbriated Aggregatibacter actinomycetemcomitans. The results showed highest values for early colonizing pioneer species, strengthening the link between adhesion forces and bacteria's role in oral biofilm development. Additionally, the correlation between biophysical cellular characteristics and SCFS results across species was analyzed. Here, distinct correlations between electrostatically driven maximum adhesion force, bacterial surface elasticity and surface charge as well as single-molecule attachment points, stretching capability and metabolic activity, could be identified. Therefore, this study provides a step towards the detailed understanding of oral bacteria initial adhesion and could support the development of infection-resistant implant materials in future.
Keywords: atomic force microscopy; bacterial adhesion; cell respiration; cell surface; dental implant; single-cell spectroscopy.