Interaction of anionic and cationic surfactants with salivary pellicles formed at solid surfaces<i>in vitro</i>

Abstract

Ellipsometry was used in order to investigate the interaction of one anionic and one cationic surfactant with salivary pellicles formed in vitro. The pellicles were formed by 30 min adsorption from 1% salivary solution and from whole saliva onto hydrophilic silica and hydrophobic methylated silica surfaces. The surfactants used were sodium dodecyl sulphate (SDS/anionic) and cetyltrimethylammonium bromide (CTAB/cationic) at concentrations of twice their critical micellar concentrations. The results indicate that the degree of coverage of the substrates by the adsorbed molecules, as well as their surface characteristics, influenced the interaction between the salivary molecules and the surfactants. The different desorbability upon rinsing and upon addition of different surfactants indicates that the pellicle is not homogenous and proteins adsorbed with varying strengths are present. There are indications that anionic surfactants are more effective in cleaning negatively charged surfaces from salivary proteins.