Concentration-dependent multiple binding sites on saliva-treated hydroxyapatite for Streptococcus sanguis

Area of Science:

• Microbiology
• Biomaterials Science
• Surface Chemistry

Background:

• Understanding bacterial adhesion to biomaterials is crucial for preventing infections.
• Saliva-coated hydroxyapatite is a common model for tooth enamel surfaces.
• Streptococcus sanguis is a key oral bacterium involved in biofilm formation.

Purpose of the Study:

• To investigate how bacterial cell concentration influences binding site and affinity estimations.
• To determine if multiple binding sites exist for Streptococcus sanguis on saliva-treated hydroxyapatite.

Main Methods:

• Adsorption isotherms were generated using a range of Streptococcus sanguis concentrations (4.7 x 10^6 to 5,960 x 10^6 cells/ml).
• Binding site number and affinity constants were calculated at different bacterial concentrations.
• Computer simulations and mathematical modeling were used to validate findings.

Main Results:

• Bacterial adsorption increased with concentration, showing a potential break in the adsorption isotherm.
• Estimates of binding sites and affinity varied significantly with bacterial concentration.
• Low concentrations yielded lower site numbers and higher affinity, suggesting saturation of high-affinity sites.

Conclusions:

• Evidence strongly supports the existence of multiple binding sites for Streptococcus sanguis on saliva-treated hydroxyapatite.
• High-affinity sites are likely specific and become saturated at lower bacterial concentrations.
• Salivary components with aggregating activity may be associated with high-affinity binding.