Collaborative Research: Effects of interfacial viscosities on flow of lung surfactants

合作研究：界面粘度对肺表面活性剂流动的影响

• 批准号: 1064644
• 负责人: Amir Hirsa
• 金额: $ 24.52万
• 依托单位: Rensselaer Polytechnic Institute
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-06-01 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1064644&HistoricalAwards=false
• 关键词: Collaborative; Research; Effects; interfacial; viscosities

Hirsa, Amir H.CBET-1064644Broader Impact and Background: The liquid lining of normal lungs is covered by surfactants. The liquid lining is essential for oxygen intake and carbon dioxide output, however without these surface-tension-reducing materials, known as surfactants, breathing would be laborious if not impossible. Aside from reducing the surface tension to minimize the work of breathing, lung surfactants also vary the surface tensionduring the breathing cycle in order to protect the alveoli against collapse on exhalation and over-expansion upon inhalation. A lack of functioning surfactants leads to respiratory distress syndrome, a potentially fatal condition in both adults and premature infants. Replacement lung surfactant therapy has already made major inroads in reducing the mortality rate amongst pre-term infants, but further improve-ments can benefit from a better understanding of the associated interfacial hydrodynamics. Present models of lung surfactant hydrodynamics neglect surface viscosities, which may make a significant contribution. There is a need to understand the role of surface viscosities in lung surfactants because at small scales, such as those of the liquid lining the alveoli, the relative effects of surface viscosities are comparable to that of surface tension. The movement of natural and artificial materials that reduce the surface tension of the liquid lining of lungs will be studied. Using advanced computer models and recently developed experimental techniques, the behavior of DPPC (dipalmitoyl phosphatidylcholine), the primary constituent of lung surfactant, will be examined. Various flow characteristics of DPPC-covered liquid layers, that have recently been revealed, will be examined in detail. The proposed project differs from previous studies in that it bridges the vast divide between the two extremes of (i) purely theoretical approaches that assume no intrinsic interfacial viscosities associated with lung surfactants and (ii) purely empirical approaches that use ad hoc equations to explain experimentally observed responses of lung surfactants. Presently, the vast majority of lung surfactant research falls into one or the other of these two camps. The former lack the ability to explain many aspects of how real lung surfactants behave and the latter lack the ability to predict how a given surfactant will respond to a different set of flow conditions.Improvements in measurement and modeling of interfacial viscosities in model surfactant systems, such as DPPC, may help one to understand better the functioning of natural lung surfactants. The capabilities developed can be subsequently used for multi-component lung surfactant systems. Ultimately, the results of this project may help speed up the development of more effective therapies. The multidisciplinary team (from mechanical engineering and mathematics), with its proven track record of productive collaboration, will provide an excellent opportunity to educate graduate and undergraduate students in interfacial hydrodynamics.Intellectual Merit. The project will develop a synergistic capability incorporating experiments and computations to account for the leading order interfacial viscoelastic hydrodynamics associated with DPPC, delineating its various flow regimes. By far, the phospholipid DPPC is the most prevalent component of lung surfactants, constituting 55{60% of lung surfactant by mass. This highly amphiphilic molecule has a hydrophilic polar head and twin hydrophobic tails, making it essentially insoluble in water. Its equilibrium interfacial properties will be measured and incorporated into a predictive model taking into account surface deformation, interfacial acceleration and spatio-temporal surface sur-factant concentration. The model will be tested directly against experiments for a canonical flow with large time-dependent changes in the interfacial area, and then used to predict the dynamics at scales too small for experimental measurements. This will provide a much-needed improved understanding and modeling of the intrinsic interfacial properties, including the elastic effects due to surface tension gradients, surface shear and dilatational viscosities, and the viscous coupling between the interfacial and bulk flows.

Hirsa，Amir H.CBET-1064644更广泛的影响和背景：正常肺的液体衬里被表面活性剂覆盖。液体衬里对于氧气的摄入和二氧化碳的排出是必不可少的，但是如果没有这些表面张力降低材料，即表面活性剂，呼吸即使不是不可能的，也会很费力。除了降低表面张力以最小化呼吸功之外，肺表面活性剂还在呼吸循环期间改变表面张力，以保护肺泡在呼气时不塌陷和在吸气时不过度扩张。缺乏功能性表面活性剂会导致呼吸窘迫综合征，这是一种在成人和早产儿中可能致命的疾病。肺表面活性物质替代疗法在降低早产儿死亡率方面已经取得了重大进展，但更好地了解相关的界面流体动力学可以进一步改善。目前的肺表面活性物质流体动力学模型忽略了表面粘度，这可能会做出显着的贡献。有必要了解表面粘度在肺表面活性剂中的作用，因为在小尺度下，如肺泡内衬的液体，表面粘度的相对影响与表面张力相当。将研究降低肺液体衬里表面张力的天然和人造材料的运动。使用先进的计算机模型和最近开发的实验技术，DPPC（二棕榈酰磷脂酰胆碱），肺表面活性物质的主要成分的行为，将被检查。DPPC覆盖的液体层，最近被发现的各种流动特性，将被详细检查。拟议的项目不同于以往的研究，因为它弥合了两个极端之间的巨大鸿沟（一）纯理论的方法，假设没有固有的界面粘度与肺表面活性剂和（ii）纯经验的方法，使用特设方程来解释实验观察到的反应肺表面活性剂。目前，肺表面活性物质研究的绝大多数福尔斯属于这两个阵营中的一个。前者缺乏解释真实的肺表面活性剂如何表现的许多方面的能力，而后者缺乏预测给定的表面活性剂将如何响应于不同的一组流动条件的能力，在模型表面活性剂系统，如DPPC中的界面粘度的测量和建模的改进，可以帮助人们更好地理解天然肺表面活性剂的功能。所开发的功能可随后用于多组分肺表面活性剂系统。最终，该项目的结果可能有助于加快更有效疗法的开发。多学科团队（来自机械工程和数学），凭借其卓有成效的合作记录，将为研究生和本科生提供界面流体力学教育的绝佳机会。智力优势。该项目将开发一种结合实验和计算的协同能力，以解释与DPPC相关的主要阶界面粘弹流体力学，描绘其各种流态。到目前为止，磷脂DPPC是肺表面活性剂的最普遍组分，占肺表面活性剂质量的55%至60%。这种高度两亲的分子具有亲水性极性头部和双疏水性尾部，使其基本上不溶于水。将测量其平衡界面性质，并将其纳入考虑表面变形、界面加速度和时空表面表面活性剂浓度的预测模型中。该模型将直接对实验进行测试的规范流与大的时间依赖性变化的界面面积，然后用于预测的动态尺度太小的实验测量。这将提供一个急需的改进的理解和建模的固有界面特性，包括弹性效应，由于表面张力梯度，表面剪切和粘性粘度，以及界面和整体流动之间的粘性耦合。