title: Solute size effects on the diffusion in biofilms of Streptococcus mutans.
abstract: The diffusion of poly(ethylene glycol) (PEG) (MW varying between 200 and 10,000), and of three different types of micelles was examined in Streptococcus mutans biofilms using infrared spectroscopy. PEGs were used because they show limited interactions with biological materials and their weight can be selected in order to cover a wide range of size. The study showed that a considerable fraction at the base of the biofilm was not accessible to the diffusing solute molecules and this inaccessible fraction was very dependent on the size of the diffusing molecules. In parallel, it was found that the diffusion coefficients of these solutes in the biofilms were less than those in water and this reduction was less pronounced for large macromolecules, an effect proposed to be related to their limited penetration. Triton X-100, a neutral detergent, forms micelles that behave like PEG, suggesting that the behaviour observed for neutral macromolecules can be extrapolated to neutral macroassemblies. However, the diffusion, as well as the penetration of sodium dodecylsulphate micelles (a negatively charged surfactant) and cetylpyridinium chloride micelles (positively charged), in the biofilms appeared to be significantly influenced by electrostatic interactions with biofilm components. The present findings provide useful insights associated with the molecular parameters required to efficiently penetrate bacterial biofilms. The study suggests a rationale for the limited bactericidal power of some antibiotics (the large ones). The restricted accessibility of macromolecules and macroassemblies to biofilms must be examined carefully in order to offer guidelines in the development of novel antibacterial treatments.
authors.affiliation: Department of Chemistry, Université de Montréal, CP 6128, Succ Centre Ville, Montréal, Québec H3C 3J7, Canada.
authors.forename: Lucie
authors.initials: L
authors.lastname: Marcotte
authors.forename: Heloise
authors.initials: H
authors.lastname: Therien-Aubin
authors.forename: Christophe
authors.initials: C
authors.lastname: Sandt
authors.forename: Jean
authors.initials: J
authors.lastname: Barbeau
authors.forename: Michel
authors.initials: M
authors.lastname: Lafleur
mesh_terms: D018441:Biofilms / Q000187:drug effects*; D002594:Cetylpyridinium; D015169:Colony Count, Microbial; D004058:Diffusion; D008823:Micelles; D017830:Octoxynol; D011092:Polyethylene Glycols / Q000737:chemistry / Q000494:pharmacology*; D012967:Sodium Dodecyl Sulfate; D055672:Static Electricity; D013295:Streptococcus mutans
chemical_list: D008823:Micelles; D012967:Sodium Dodecyl Sulfate; D011092:Polyethylene Glycols; D017830:Octoxynol; D002594:Cetylpyridinium