Measurement of the surface free energy of bacterial cell surfaces and its relevance for adhesion

TLDR

The study presents an experimental method to measure contact angles on bacterial layers deposited on cellulose triacetate filters. Using water, water‑n‑propanol mixtures, and alpha‑bromonaphthalene, the authors calculated surface free energies of oral bacteria and then derived interfacial free energies of adhesion to tooth surfaces. The measured surface free energies differed by 30–40 erg cm⁻² among four oral bacterial species, and adhesion was found to be energetically unfavorable when enamel surface free energy fell below 50 erg cm⁻².

Abstract

An experimental technique is described to determine contact angles on bacterial layers deposited on cellulose triacetate filters. Measurements with water, water-n-propanol mixtures, and alpha-bromonaphthalene were employed to calculate surface free energies of various oral bacteria. Differences of 30 to 40 erg cm-2 were obtained for four different bacterial species isolated from the human oral cavity, if the concept of dispersion and polar surface free energies is applied. The free energies obtained were used to calculate interfacial free energies of adhesion of these bacteria from saliva onto tooth surfaces. Bacterial adhesion is energetically unfavorable, if the enamel surface free energy is less than 50 erg cm-2.