Diffusion of Substances Through the Brain

描述（由申请人提供）：长期目标是了解脑细胞外间隙（ECS）中物质扩散的生物物理学。在生物医学上，这一建议将提高对大脑中药物传递的障碍和影响ECS中化学信号的因素的理解。ECS包括脑细胞之间的狭窄间隙空间的集合体，并含有长链糖基化分子的细胞外基质（ECM）。ECS中的扩散障碍的特征在于复合参数，曲折度，其包括a）几何路径长度的增加，B）死空间微域，c）阻塞和间质粘度，d）与ECM的特异性结合和e）与ECM上的固定负电荷的非特异性相互作用。这些因素将探讨通过扩散的物质，结合四甲基铵和其他离子在体内和脑切片的实时离子电渗的荧光大分子的集成光学成像。 目标1：能穿过ECS的最大分子或粒子是什么？初步实验表明，直径为40 nm的大分子可以在体内扩散。将在正常和经药物修饰的ECS中探索分子大小的进一步范围。 目的2：特异性ECM结合在多大程度上阻碍了生物学重要分子的扩散？ 天然存在的模型蛋白质乳铁蛋白的扩散将测定与ECM的硫酸乙酰肝素蛋白聚糖的特异性结合。 目标3：ECS中是否存在电荷歧视？这一目的将研究扩散的单价和多价离子和生物胺与ECM的固定负电荷的非特异性相互作用。 目标4：模型死空间微区，结合和电荷相互作用和统一的软件。将开发数据分析的模型和算法，并统一定制软件，以方便外部用户

DESCRIPTION (provided by applicant): The long-term goal is to understand the biophysics of substance diffusion in brain extracellular space (ECS). Biomedically, this proposal will enhance understanding of impediments to drug delivery in brain and factors that affect chemical signaling in the ECS. The ECS comprises the ensemble of narrow interstitial spaces between brain cells and harbors an extracellular matrix (ECM) of long chain glycosylated molecules. Hindrance to diffusion in the ECS is characterized by a composite parameter, the tortuosity, that includes a) increase in geometric path-length, b) dead-space microdomains, c) obstruction and interstitial viscosity, d) specific binding to ECM and e) nonspecific interaction with fixed negative charges on the ECM. These factors will be explored through the diffusion of substances using integrative optical imaging of fluorescent macromolecules combined with realtime iontophoresis of tetramethylammonium and other ions both in vivo and in brain slices. Aim 1: What is the largest molecule or particle that can traverse the ECS? Preliminary experiments show that macromolecules with 40 nm diameter can diffuse in vivo. A further range of molecular sizes will be explored in normal and osmotically modified ECS. Aim 2: How much does specific ECM binding hinder diffusion of biologically important molecules? Diffusion of the naturally occurring model protein, lactoferrin, will assay specific binding with heparan sulfate proteoglycans of the ECM. Aim 3: Is there charge discrimination in the ECS? This aim will study the non-specific interaction of diffusing mono- and multivalent ions and biogenic amines with the fixed negative charges of the ECM. Aim 4: Model dead-space microdomains, binding and charge interaction and unify software. Models and algorithms for data analysis will be developed and the custom software unified to facilitate outside users