A biocoating confines nongrowing, metabolically active bacteria within a synthetic colloidal polymer (i.e., latex) film. Bacteria encapsulated inside biocoatings can perform useful functions, such as a biocatalyst in wastewater treatment. A biocoating needs to have a high permeability to allow a high rate of mass transfer for rehydration and the transport of both nutrients and metabolic products. It therefore requires an interconnected porous structure. Tuning the porosity architecture is a challenge. Here, we exploited rigid tubular nanoclays (halloysite) and nontoxic latex particles (with a relatively high glass transition temperature) as the colloidal “building blocks” to tailor the porosity inside biocoatings containing Escherichia coli bacteria as a model organism. Electron microscope images revealed inefficient packing of the rigid nanotubes and proved the existence of nanovoids along the halloysite/polymer interfaces. Single-cell observations using confocal laser scanning microscopy provided evidence for metabolic activity of the E. coli within the biocoatings through the expression of a yellow fluorescent protein. A custom-built apparatus was used to measure the permeability of a fluorescein sodium salt in the biocoatings. Whereas there was no measurable permeability in a coating made from only latex particles, the permeability coefficient of the composite biocoatings increased with increasing halloysite content up to a value of 1 × 10^–4 m h^–1. The effects of this increase in permeability was demonstrated through a specially developed resazurin reduction assay. Bacteria encapsulated in halloysite composite biocoatings had statistically significant higher metabolic activities in comparison to bacteria encapsulated in a nonoptimized coating made from latex particles alone.

中文翻译：

---

在胶体生物涂层中引入孔隙以增加细菌活力。

生物涂层将非生长的、代谢活跃的细菌限制在合成胶体聚合物（即乳胶）薄膜内。包裹在生物涂层内的细菌可以发挥有用的功能，例如废水处理中的生物催化剂。生物涂层需要具有高渗透性，以允许高速率的质量传递以进行再水化以及营养物质和代谢产物的运输。因此，它需要一个相互连接的多孔结构。调整孔隙度结构是一项挑战。在这里，我们利用刚性管状纳米粘土（埃洛石）和无毒乳胶颗粒（具有相对较高的玻璃化转变温度）作为胶体“构件”来调整含有大肠杆菌的生物涂层内部的孔隙率细菌作为模式生物。电子显微镜图像显示刚性纳米管的填充效率低下，并证明沿埃洛石/聚合物界面存在纳米空隙。使用共聚焦激光扫描显微镜的单细胞观察通过黄色荧光蛋白的表达为生物涂层内大肠杆菌的代谢活性提供了证据。使用定制设备测量生物涂层中荧光素钠盐的渗透性。虽然在仅由乳胶颗粒制成的涂层中没有可测量的渗透性，但复合生物涂层的渗透系数随着埃洛石含量的增加而增加，最高可达 1 × 10 ^–4 mh ^–1. 通过特别开发的刃天青还原试验证明了这种渗透性增加的影响。与仅由乳胶颗粒制成的未经优化的涂层中包裹的细菌相比，包裹在埃洛石复合生物涂层中的细菌具有统计学上显着更高的代谢活性。