背景:圆窗膜(RWM)通过局部应用充当内耳中治疗剂的主要生物屏障。以往对内耳纳米给药系统的研究主要集中在其在内耳的药代动力学和分布,但很少与RWM互动。阐明纳米颗粒载体跨RWM的运输机制将为旨在满足其临床应用需求的纳米药物递送系统的最佳设计提供更多启示。
方法:通过乳化溶剂蒸发法制备包封香豆素-6的聚乳酸-乙醇酸共聚物纳米颗粒(PLGANPs)。我们利用共聚焦激光扫描显微镜(CLSM)结合透射电子显微镜研究了PLGANPs在RWM中的转运途径。同时,还确定了整个RWM中NPs的浓度和时间依赖性。通过各种内吞抑制剂经典地分析了NPs通过该膜界面的内吞机制。使用CLSM扫描显微镜共定位分析评估NP在溶酶体中的细胞内定位。使用高尔基体相关抑制剂来探讨高尔基体和内质网(ER)在NPs排出细胞中的功能。
结果:PLGANP在本文中经由跨细胞途径通过夹心样结构的RWM转运到外淋巴液中。NP主要通过巨细胞胞吞作用和小窝蛋白介导的内吞途径内化。在被内在化之后,内吞的货物被包裹在溶酶体区室和/或内质网/高尔基体中,它们介导了NPs的胞吐释放。
结论:第一次,我们显示了NPs在RWM中的易位路线,为合理制作具有较好治疗效果的内耳纳米颗粒载体提供了指导。
BACKGROUND: The round window membrane (RWM) functions as the primary biological barrier for therapeutic agents in the inner ear via local application. Previous studies on inner ear nano-drug delivery systems mostly focused on their pharmacokinetics and distribution in the inner ear, but seldom on the interaction with the RWM. Clarifying the transport mechanism of nanoparticulate carriers across RWM will shed more light on the optimum design of nano-drug delivery systems intended for meeting demands for their clinical application.
METHODS: The poly (lactic-co-glycolic acid) nanoparticles (PLGA NPs) encapsulating coumarin-6 were prepared by emulsifying solvent evaporation method. We utilized confocal laser scanning microscope (CLSM) in combination with transmission electron microscope to investigate the transport pathway of PLGA NPs in the RWM. Simultaneously, the concentration and time dependence of NPs across the RWM were also determined. The endocytic mechanism of NPs through this membrane interface was classically analyzed by means of various endocytic inhibitors. The intracellular location of NPs into lysosomes was evaluated using CLSM scanning microscope colocalization analysis. The Golgi-related inhibitors were employed to probe into the function of Golgi and endoplasmic reticulum (ER) in the discharge of NPs out of cells.
RESULTS: PLGA NPs were herein transported through the RWM of a sandwich-like structure into the perilymph via the transcellular pathway. NPs were internalized predominantly via macropinocytosis and caveolin-mediated endocytic pathways. After being internalized, the endocytosed cargos were entrapped within the lysosomal compartments and/or the endoplasmic reticulum/Golgi apparatus which mediated the exocytotic release of NPs.
CONCLUSIONS: For the first time, we showed the translocation itinerary of NPs in RWM, providing a
guideline for the rational fabrication of inner ear nanoparticulate carriers with better therapeutic effects.