Optimization of an hydroxyapatite adhesion assay for Streptococcus sanguis.

Area of Science:

• Microbiology
• Biomaterials Science
• Oral Health Research

Background:

• Previous studies compared Streptococcus sanguis adhesion to saliva-coated hydroxyapatite (SHA) and buffer-coated hydroxyapatite (HA).
• The hypotonic buffer used previously may not offer optimal parameters for quantitative adhesion estimation.
• Assay optimization is needed for sensitive detection of salivary effects and environmental growth condition impacts on S. sanguis adhesion.

Purpose of the Study:

• To optimize in vitro assay conditions for quantifying Streptococcus sanguis adhesion to hydroxyapatite.
• To determine the optimal buffer composition, pH, and ionic strength for S. sanguis adhesion studies.
• To investigate the influence of various ions and compounds on bacterial adhesion to SHA and HA.

Main Methods:

• Utilized [3H]thymidine-labeled Streptococcus sanguis.
• Compared bacterial adhesion to saliva-coated hydroxyapatite (SHA) and buffer-coated hydroxyapatite (HA) beads.
• Varied bacterial concentration, pH, ionic strength, and cation/anion concentrations.

Main Results:

• A significant difference in adhesion between SHA and HA was observed at high bacterial concentrations, with SHA showing twice the adhesion.
• Optimal pH for adsorption to both SHA and HA was determined to be 6.
• High concentrations of monovalent cations inhibited adhesion to SHA, while acetate and fluoride inhibited adhesion to both SHA and HA.

Conclusions:

• The optimal buffer for studying in vitro adhesion of S. sanguis to SHA consists of 2 mM phosphate buffer at pH 6, containing 5 mM KCl and 1 mM CaCl2.
• Bacterial concentration significantly influences adhesion patterns, particularly the distinction between SHA and HA.
• Specific ions like acetate and fluoride impact bacterial adhesion, suggesting potential interactions with the hydroxyapatite surface.