Structures and mechanisms in clay nanopore trapping of structurally-different fluoroquinolone antimicrobials.
Structures and mechanisms in clay nanopore trapping of structurally-different fluoroquinolone antimicrobials.
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DOI：
10.1016/j.jcis.2017.11.020
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发表时间：
2018-03
影响因子：
9.9
通讯作者：
F. E. Okaikue-Woodi;Sabrina E. Kelch;Michael P. Schmidt;Carmen Enid Martínez;R. Youngman;L. Aristilde
中科院分区：
文献类型：
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作者：
F. E. Okaikue-Woodi;Sabrina E. Kelch;Michael P. Schmidt;Carmen Enid Martínez;R. Youngman;L. Aristilde
蒙脱石粘土纳米颗粒与土壤和沉积物中抗菌剂的保留有关;这些粘土也被检查为生理系统中的药物载体。阳离子交换被认为是蒙脱石纳米孔内抗菌剂的主要吸附机制。然而，最近的研究推测酸碱化学和吸附结构的双重作用。使用典型的蒙脱石粘土蒙脱石，我们采用X射线衍射（XRD），核磁共振，衰减全反射-傅里叶变换红外光谱和分子动力学模拟的组合来研究两种结构不同的氟喹诺酮（FQ）抗菌剂的层间纳米孔捕获具有相似的酸碱化学：环丙沙星（第一代FQ）和氟喹诺酮（第三代FQ）。更大的吸附在pH 5.0比在pH 7.0的两个FQs是一致的阳离子交换带正电荷的物种。然而，粘土表现出近两倍高的吸附能力比环丙沙星的诺氟沙星。XRD数据显示，这种差异伴随着粘土夹层内的阿西沙星的增强捕获。使用XRD确定的纳米孔尺寸，我们进行了分子动力学模拟的吸附有利的模型吸附物，这表明，环丙沙星吸附平行于粘土表面，但氟诺沙星通过倾斜的构象在纳米孔。这些构象导致更慢的交换比快速交换钠与环丙沙星的复合物相比，阿西沙星。这些不同的钠离子也被23 Na核磁共振捕获。此外，模拟吸附物揭示了不同的络合相互作用，证实了红外光谱。因此，除了酸碱化学，我们的研究结果表明，不同的吸附物结构控制粘土纳米孔内的抗菌剂捕获，这可以促进环境基质中的持久性和生物系统中的稳定递送。
Smectite clay nanoparticles are implicated in the retention of antimicrobials within soils and sediments; these clays are also inspected as drug carriers in physiological systems. Cation exchange is considered the primary adsorption mechanism of antimicrobials within smectite nanopores. However, a dual role of acid-base chemistry and adsorptive structures is speculated by recent studies. Using the prototypical smectite clay montmorillonite, we employed a combination of X-ray diffraction (XRD), nuclear magnetic resonance, attenuated total reflectance-Fourier transform infrared spectroscopy, and molecular dynamics simulations to investigate the interlayer nanopore trapping of two structurally-different fluoroquinolone (FQ) antimicrobials with similar acid-base chemistry: ciprofloxacin (a first-generation FQ) and moxifloxacin (a third-generation FQ). Greater sorption at pH 5.0 than at pH 7.0 for both FQs was consistent with cation-exchange of positively-charged species. However, the clay exhibited a near twofold higher sorption capacity for moxifloxacin than for ciprofloxacin. This difference was shown by the XRD data to be accompanied by enhanced trapping of moxifloxacin within the clay interlayers. Using the XRD-determined nanopore sizes, we performed molecular dynamics simulations of thermodynamically-favorable model adsorbates, which revealed that ciprofloxacin was adsorbed parallel to the clay surface but moxifloxacin adopted a tilted conformation across the nanopore. These conformations resulted in more slowly-exchanged than quickly-exchanged Na complexes with ciprofloxacin compared with moxifloxacin. These different Na populations were also captured by23Na nuclear magnetic resonance. Furthermore, the simulated adsorbates uncovered different complexation interactions that were corroborated by infrared spectroscopy. Therefore, beyond acid-base chemistry, our findings imply that distinct adsorbate structures control antimicrobial trapping within clay nanopores, which can promote persistence in environmental matrices and stable delivery in biological systems.