Layered double hydroxides for controlled fluoride release

Abstract This study aims to develop a nano-sized fluoridated layered double hydroxide (LDH)-based release system via hydrothermal treatment for the controlled delivery of fluoride (F-) ions in the oral environment. The synthesis of conventional LDH-type (C-LDH) precursor nanomaterials was conducted using a co-precipitation method at constant pH, and the nanoparticulate-LDH (N-LDH) was synthesized by a hydrothermal procedure. Fluoride LDH (F-LDH) products were obtained through indirect synthesis using the precursor ion-exchange technique by varying the agitation time (2 and 24 h) and temperature (25 and 40 °C) to produce 12 material samples. The materials were characterized by energy dispersive x-ray, hexamethyldisilazane, digital radiography x-ray, Fourier-transform infrared, thermogravimetric analysis, and scanning electron microscopy. Additionally, the F-release kinetic profile was evaluated for 21 d in neutral and acid media with mathematical model analysis. Products with varying F-quantities were obtained, revealing specific release profiles. In general, there was a higher F-release in the acid medium, with emphasis on F-LDH-8. Fluoride-LDH and controlled fluoride delivery was successfully obtained, proving the potential of these nanomaterials as alternative anti-caries agents.

摘要
本研究旨在通过水热法制备一种氟化纳米层状双氢氧化物（layered double hydroxide, LDH）基控释体系，用于口腔环境中氟离子（fluoride, F⁻）的可控递送。常规LDH型（C-LDH）前驱体纳米材料采用恒pH共沉淀法合成，纳米颗粒LDH（N-LDH）则通过水热工艺制备。通过前驱体离子交换法间接合成氟化LDH（F-LDH）产物，通过改变搅拌时间（2 h与24 h）和反应温度（25 ℃与40 ℃），共得到12组材料样品。采用能量色散X射线、六甲基二硅氮烷、数字化X射线摄影、傅里叶变换红外光谱、热重分析以及扫描电子显微镜对材料进行表征。此外，通过数学模型分析，对中性与酸性介质中21天的氟离子释放动力学曲线进行了评估。成功制备出氟负载量各异的产物，各产物均展现出特定的释放曲线。总体而言，酸性介质中的氟离子释放量更高，其中F-LDH-8的释放效果最为突出。本研究成功制备出氟化LDH材料与氟离子可控递送体系，证实了这类纳米材料作为新型抗龋制剂的应用潜力。