title: Mass transport of macromolecules within an in vitro model of supragingival plaque.
abstract: The aim of this study was to examine the diffusion of macromolecules through an in vitro biofilm model of supragingival plaque. Polyspecies biofilms containing Actinomyces naeslundii, Fusobacterium nucleatum, Streptococcus oralis, Streptococcus sobrinus, Veillonella dispar, and Candida albicans were formed on sintered hydroxyapatite disks and then incubated at room temperature for defined periods with fluorescent markers with molecular weights ranging from 3,000 to 900,000. Subsequent examination by confocal laser scanning microscopy revealed that the mean square penetration depths for all tested macromolecules except immunoglobulin M increased linearly with time, diffusion coefficients being linearly proportional to the cube roots of the molecular weights of the probes (range, 10,000 to 240,000). Compared to diffusion in bulk water, diffusion in the biofilms was markedly slower. The rate of diffusion for each probe appeared to be constant and not a function of biofilm depth. Analysis of diffusion phenomena through the biofilms suggested tortuosity as the most probable explanation for retarded diffusion. Selective binding of probes to receptors present in the biofilms could not explain the observed extent of retardation of diffusion. These results are relevant to oral health, as selective attenuated diffusion of fermentable carbohydrates and acids produced within dental plaque is thought to be essential for the development of carious lesions.
authors.affiliation: Institute for Oral Microbiology and General Immunology, University of Zürich, Plattenstrasse 11, CH-8028 Zürich, Switzerland. thurnher@zzmk.unizh.ch
authors.forename: Thomas
authors.initials: T
authors.lastname: Thurnheer
authors.forename: Rudolf
authors.initials: R
authors.lastname: Gmür
authors.forename: Stuart
authors.initials: S
authors.lastname: Shapiro
authors.forename: Bernhard
authors.initials: B
authors.lastname: Guggenheim
mesh_terms: D000190:Actinomyces / Q000254:growth & development; D000418:Albumins / Q000378:metabolism; D018441:Biofilms / Q000254:growth & development*; D002176:Candida albicans / Q000254:growth & development; D003773:Dental Plaque / Q000382:microbiology*; D003911:Dextrans / Q000378:metabolism; D004058:Diffusion; D005456:Fluorescent Dyes / Q000378:metabolism; D016967:Fusobacterium nucleatum / Q000254:growth & development; D005881:Gingiva / Q000382:microbiology*; D046911:Macromolecular Substances; D008954:Models, Biological; D019533:Streptococcus oralis / Q000254:growth & development; D016986:Streptococcus sobrinus / Q000254:growth & development; D014678:Veillonella / Q000254:growth & development
chemical_list: D000418:Albumins; D003911:Dextrans; D005456:Fluorescent Dyes; D046911:Macromolecular Substances