AFM ANALYSIS OF BACTERIAL ADHESION TO HYDROXYLAPATITE SURFACES

Calcified tissues such as teeth and bones primarily consist of poorly ordered carbonate-rich hydroxylapatite (HAP). Unlike bone tissue, which can regenerate, once a tooth is ruptured and dentine removed there is no regeneration. Bacteria, including Streptococcus mutans are part of the normal microflora of the oral cavity. They are pathogens that can cause plaque and initiate dental caries. Streptococcus mutans are the first bacteria that adhere to the surface of teeth forming a layer that allows other bacteria to adhere and form plaque. This study proposes to examine the adhesion forces between Streptococcus mutans and hydroxylapatite by means of atomic force microscopy (AFM). Individual bacterial cells will be isolated on to AFM cantilevers using a chemical linker molecule. Adhesion forces of Streptococcus mutans to polished hydroxylapatite surface will be examined under various aqueous chemistry conditions. We will use naturally occurring cut and polished single HAP crystals as well as synthetic HAP samples. Forces will be measured in various synthetic aqueous solutions and in human saliva as a function of bacteria-HAP separation distance. Mechanisms of plaque formation and bacterial adhesion are not entirely understood. This research will show the nature of adhesion between Streptococcus mutans and HAP. Furthermore, we will be able to identify aqueous conditions that are least favorable for bacterial adhesion and biofilm formation.