Department of Civil and Environmental Engineering, Rice University, Houston, USA; Nanosystems Engineering Research Center for Nanotechnology-Enabled Water Treatment, USA.
Department of Chemistry, Rice University, Houston, USA; Nanosystems Engineering Research Center for Nanotechnology-Enabled Water Treatment, USA.
Water Res. 2022 Oct 1;224:119070. doi: 10.1016/j.watres.2022.119070. Epub 2022 Sep 7.
Biofilms in water storage systems may harbor pathogens that threaten public health. Chemical disinfectants are marginally effective in eradicating biofilms due to limited penetration, and often generate harmful disinfection byproducts. To enhance biofouling mitigation in household water storage tanks, we encapsulated bacteriophages (phages) in chitosan crosslinked with tri-polyphosphate and 3-glycidoxypropyltrimethoxysilane. Phages served as self-propagating green biocides that exclusively infect bacteria. This pH-responsive encapsulation (244 ± 11 nm) enabled autonomous release of phages in response to acidic pH associated with biofilms (corroborated by confocal microscopy with pH-indicator dye SNARF-4F), but otherwise remained stable in pH-neutral tap water for one month. Encapsulated phages instantly bind to plasma-treated plastic and fiberglass surfaces, providing a facile coating method that protects surfaces highly vulnerable to biofouling. Biofilm formation assays were conducted in tap water amended with 200 mg/L glucose to accelerate growth and attachment of Pseudomonas aeruginosa, an opportunistic pathogen commonly associated with biofilms in drinking water distribution and storage systems. Biofilms formation on plastic surfaces coated with encapsulated phages decreased to only 6.7 ± 0.2% (on a biomass basis) relative to the uncoated controls. Likewise, biofilm surface area coverage (4.8 ± 0.2 log CFU/mm) and live/dead fluorescence ratio (1.80) were also lower than the controls (6.6 ± 0.2 log CFU/mm and live/dead ratio of 11.05). Overall, this study offers proof-of-concept of a chemical-free, easily implementable approach to control problematic biofilm-dwelling bacteria and highlights benefits of this bottom-up biofouling control approach that obviates the challenge of poor biofilm penetration by biocides.
水存储系统中的生物膜可能藏匿着威胁公众健康的病原体。由于穿透能力有限，化学消毒剂在消除生物膜方面效果有限，而且往往会产生有害的消毒副产物。为了增强家庭水存储罐中的生物结垢缓解效果，我们将噬菌体（phages）封装在壳聚糖中，壳聚糖通过三聚磷酸和 3-缩水甘油丙基三甲氧基硅烷交联。噬菌体作为自我传播的绿色生物杀灭剂，专门感染细菌。这种 pH 响应性封装（244 ± 11nm）使噬菌体能够在与生物膜相关的酸性 pH 下自主释放（通过带有 pH 指示剂染料 SNARF-4F 的共聚焦显微镜证实），但在 pH 中性的自来水环境中一个月内仍保持稳定。封装后的噬菌体可立即与等离子体处理过的塑料和玻璃纤维表面结合，提供一种简便的涂层方法，可保护易受生物结垢影响的表面。在添加了 200mg/L 葡萄糖的自来水中进行生物膜形成实验，以加速铜绿假单胞菌（一种与饮用水分配和储存系统中的生物膜相关的机会性病原体）的生长和附着。与未涂层的对照相比，涂有封装噬菌体的塑料表面上生物膜的形成减少到仅 6.7 ± 0.2%（基于生物量）。同样，生物膜表面积覆盖率（4.8 ± 0.2logCFU/mm）和死活荧光比（1.80）也低于对照（6.6 ± 0.2logCFU/mm 和死活比为 11.05）。总的来说，这项研究提供了一个无化学物质、易于实施的控制有问题的生物膜栖息细菌的方法的概念验证，并强调了这种自下而上的生物结垢控制方法的好处，该方法避免了生物杀灭剂对生物膜穿透能力差的挑战。
