Department of Chemistry, University of Montreal, P.O. Box 6128, Succursale Centre-ville, Montreal, QC H3C3J7, Canada.
Antimicrob Agents Chemother. 2011 Mar;55(3):1075-81. doi: 10.1128/AAC.01329-10. Epub 2010 Dec 28.
In biofilms, diffusion may limit the chemical activity of nutrients, toxic compounds, and medicines. This study provides direct, noninvasive insight into the factors that will most effectively limit the transport of antibiotics and biocides in biofilms. Self-diffusion coefficients have been determined for a number of fluorescent probes in biofilms of Streptococcus mutans using fluorescence correlation spectroscopy. The effects of probe size and charge and the roles of biofilm pH, ionic strength, and heterogeneity were studied systematically. The relative diffusion coefficients (D in the biofilm divided by that in water) decreased with increasing probe size (3,000-molecular-weight [3K], 10K, 40K, 70K, and 2,000K dextrans). Studies using variably charged substrates (tetramethylrhodamine, Oregon Green, rhodamine B, and rhodamine 6G) showed that the self-diffusion coefficients decreased with an increasing negative charge of the fluorescent probes. No significant effect was observed for changes to the ionic strength (10⁻⁴ to 10⁻¹ M) or pH (4 to 9) of the biofilm. Biofilm heterogeneity was responsible for variations of ca. one order of magnitude in the diffusion coefficients.
在生物膜中，扩散可能会限制营养物质、有毒化合物和药物的化学活性。本研究直接、非侵入性地深入了解了哪些因素会最有效地限制抗生素和杀生剂在生物膜中的传输。本研究使用荧光相关光谱法测定了变形链球菌生物膜中多种荧光探针的自扩散系数。系统研究了探针大小和电荷的影响以及生物膜 pH 值、离子强度和异质性的作用。相对扩散系数（生物膜中的 D 与水中的 D 之比）随探针尺寸（3000 分子量 [3K]、10K、40K、70K 和 2000K 葡聚糖）的增加而降低。使用带有可变电荷的底物（四甲基罗丹明、Oregon Green、罗丹明 B 和罗丹明 6G）的研究表明，自扩散系数随荧光探针的负电荷增加而降低。生物膜的离子强度（10⁻⁴ 至 10⁻¹ M）或 pH 值（4 至 9）的变化对其没有明显影响。生物膜的异质性是导致扩散系数变化约一个数量级的原因。
