Diffusion of Submicron Particles on Biological Surfactant Monolayers Governed by the Viscoelasticity and Interfacial Dynamics.

IF 2.9 2区 化学 Q3 CHEMISTRY, PHYSICAL
Yang Liu, Xu Zheng, Weiguo Liang, Feng Gao, Yinghao Wang
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Abstract

The diffusion of microscale and nanoscale particles on biological membranes plays a critical role in understanding various physiologic processes and optimizing drug delivery. In this study, we investigate the diffusive motion of submicron particles on in vitro porcine pulmonary surfactant monolayers at the air-water interface using single-particle tracking. The viscoelastic response of the monolayer becomes apparent only when particle sizes fall below the Saffman and Delbrück length. Hydrodynamic and nonhydrodynamic interfacial dynamics induce distinct anomalous diffusion behaviors for small and large particles, respectively. For smaller particles, their thermal velocities approach the minimum phase velocity of interfacial capillary waves, causing a hydrodynamic wave drag, whose magnitude can be approximately modeled using the sudden accelerated/decelerated rectilinear motion of an object at the interface. In contrast, larger particles do not exhibit wave drag due to their lower thermal velocities. Instead, their displacement correlation functions reveal unusually slow-decaying oscillations─a phenomenon fundamentally stemmed from nanoscale contact-line interfacial dynamics. These oscillations are linked to the diffusion coefficient that varies instantaneously with the particle's immersion depth. By performing Langevin dynamics simulations of the particle's perpendicular motion, we confirmed that the oscillation period precisely coincides with the cyclic time of the particle's motion along the interfacial normal direction. These simulations explicitly account for subtle contact-line perturbations to the interfacial free energy, which arise from nanoscale surface heterogeneity of the particle. This behavior demonstrates strong dynamic coupling between in-plane and out-of-plane particle motions. Crucially, the oscillation amplitude becomes magnified when the particle's transverse displacement per unit time decreases, explaining why these oscillations are exclusively observable in larger particles. The displacement probability distributions (DPDs) remain non-Gaussian even at long elapsed times when the diffusion becomes linear. This non-Gaussianity stems from variations in the diffusion coefficients of individual particles, which originate from the heterogeneity of the monolayer's structure.

亚微米颗粒在生物表面活性剂单分子膜上的扩散受粘弹性和界面动力学控制。
微纳米粒子在生物膜上的扩散在理解各种生理过程和优化给药过程中起着至关重要的作用。在这项研究中,我们研究了亚微米颗粒在体外猪肺表面活性剂单层空气-水界面上的扩散运动。只有当颗粒尺寸低于Saffman和delbr长度时,单层的粘弹性响应才会变得明显。水动力和非水动力界面动力学分别诱导了小颗粒和大颗粒明显的异常扩散行为。对于较小的颗粒,它们的热速度接近界面毛细波的最小相速度,造成水动力波阻力,其大小可以用界面处物体突然加速/减速的直线运动近似模拟。相比之下,较大的颗粒由于其较低的热速度而不表现出波阻。相反,它们的位移相关函数显示出不同寻常的缓慢衰减振荡──这种现象基本上源于纳米级接触线界面动力学。这些振荡与扩散系数有关,扩散系数随粒子浸入深度的瞬间变化而变化。通过对粒子垂直运动的朗之万动力学模拟,我们证实了振荡周期与粒子沿界面法向运动的循环时间精确吻合。这些模拟清楚地说明了细微的接触线微扰对界面自由能的影响,这是由粒子的纳米级表面非均质性引起的。这一行为表明了平面内和平面外粒子运动之间的强动态耦合。至关重要的是,当粒子单位时间的横向位移减小时,振荡幅度就会放大,这就解释了为什么这些振荡只在较大的粒子中可见。当扩散变为线性时,位移概率分布(DPDs)即使经过很长时间也保持非高斯分布。这种非高斯性源于单个粒子的扩散系数的变化,而扩散系数的变化源于单层结构的非均匀性。
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来源期刊
CiteScore
5.80
自引率
9.10%
发文量
965
审稿时长
1.6 months
期刊介绍: An essential criterion for acceptance of research articles in the journal is that they provide new physical insight. Please refer to the New Physical Insights virtual issue on what constitutes new physical insight. Manuscripts that are essentially reporting data or applications of data are, in general, not suitable for publication in JPC B.
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