Thurnheer Thomas, Gmür Rudolf, Shapiro Stuart, Guggenheim Bernhard
Institute for Oral Microbiology and General Immunology, University of Zürich, Plattenstrasse 11, CH-8028 Zürich, Switzerland.
Appl Environ Microbiol. 2003 Mar;69(3):1702-9. doi: 10.1128/AEM.69.3.1702-1709.2003.
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.
本研究的目的是通过体外龈上菌斑生物膜模型来检测大分子的扩散情况。含有内氏放线菌、具核梭杆菌、口腔链球菌、远缘链球菌、差异韦荣球菌和白色念珠菌的多菌种生物膜在烧结羟基磷灰石圆盘上形成，然后在室温下与分子量范围为3000至900000的荧光标记物一起孵育特定时间。随后通过共聚焦激光扫描显微镜检查发现，除免疫球蛋白M外，所有测试大分子的均方渗透深度随时间呈线性增加，扩散系数与探针分子量的立方根呈线性比例关系（范围为10000至240000）。与在大量水中的扩散相比，在生物膜中的扩散明显较慢。每种探针的扩散速率似乎是恒定的，且不是生物膜深度的函数。对通过生物膜的扩散现象分析表明，曲折度是扩散受阻最可能的解释。探针与生物膜中存在的受体的选择性结合无法解释观察到的扩散受阻程度。这些结果与口腔健康相关，因为牙菌斑内产生的可发酵碳水化合物和酸的选择性衰减扩散被认为对龋病病变的发展至关重要。
