Zeng Chuanzi, Kobayashi Motoyoshi
Graduate School of Science and Technology, University of Tsukuba, Tsukuba 305-8572, Ibaraki, Japan.
Institute of Life and Environmental Sciences, University of Tsukuba, Tsukuba 305-8572, Ibaraki, Japan.
Nanomaterials (Basel). 2025 Mar 3;15(5):389. doi: 10.3390/nano15050389.
The transport and fate of antibiotics are significantly influenced by co-existing colloidal and nanosized substances, such as clay particles. Montmorillonite, a common clay mineral with a thin nano-sheet-like structure, enhances antibiotic (e.g., ciprofloxacin) mobility due to its strong adsorption properties. Nevertheless, little is known about how ciprofloxacin systematically influences the charging and aggregation properties of montmorillonite. This study examines the effect of ciprofloxacin on the electrophoretic mobility and hydrodynamic diameter of Na-montmorillonite under varying pH levels and NaCl concentrations. Results show ciprofloxacin promotes aggregation and alters the surface net charge of Na-montmorillonite at acidic to neutral pH, where ciprofloxacin is positively charged. At higher pH levels, where ciprofloxacin is negatively charged, no significant effects are observed. The observed aggregation behaviors align with predictions based on the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Specifically, the slow aggregation regime, the fast aggregation regime, and the critical coagulation concentration are identified. The relationship between critical coagulation ionic strength and electrokinetic surface charge density is well explained by the DLVO theory with the Debye-Hückel approximations. Additionally, non-DLVO interactions are inferred. At low NaCl and ciprofloxacin concentrations, minimal changes in aggregation and surface charge suggest dispersed montmorillonite may facilitate ciprofloxacin transport, raising environmental concerns.
抗生素的迁移和归宿受到共存的胶体和纳米级物质（如粘土颗粒）的显著影响。蒙脱石是一种常见的具有薄纳米片状结构的粘土矿物，因其强大的吸附特性而增强了抗生素（如环丙沙星）的迁移性。然而，关于环丙沙星如何系统地影响蒙脱石的带电和聚集特性，人们所知甚少。本研究考察了在不同pH值和NaCl浓度下，环丙沙星对钠基蒙脱石电泳迁移率和流体动力学直径的影响。结果表明，在酸性至中性pH值下，环丙沙星带正电荷，它促进了钠基蒙脱石的聚集并改变了其表面净电荷。在较高pH值下，环丙沙星带负电荷，未观察到显著影响。观察到的聚集行为与基于德亚金-朗道-韦弗-奥弗贝克（DLVO）理论的预测一致。具体而言，确定了慢速聚集 regime、快速聚集 regime 和临界聚沉浓度。DLVO 理论结合德拜-休克尔近似很好地解释了临界聚沉离子强度与电动表面电荷密度之间的关系。此外，推断出存在非 DLVO 相互作用。在低 NaCl 和环丙沙星浓度下，聚集和表面电荷的变化最小，这表明分散的蒙脱石可能会促进环丙沙星的迁移，引发环境问题。
