Department of Physics and Astronomy and LaserLab, Vrije Universiteit Amsterdam , Amsterdam, 1081 HV, The Netherlands.
Department of Oral Function and Restorative Dentistry, Academic Centre for Dentistry Amsterdam (ACTA), Research Institute MOVE, University of Amsterdam and Vrije Universiteit Amsterdam , Amsterdam, 1081 LA, The Netherlands.
ACS Nano. 2017 Mar 28;11(3):2628-2636. doi: 10.1021/acsnano.6b07302. Epub 2017 Mar 14.
Nanovesicles (∼100 nm) are ubiquitous in cell biology and an important vector for drug delivery. Mechanical properties of vesicles are known to influence cellular uptake, but the mechanism by which deformation dynamics affect internalization is poorly understood. This is partly due to the fact that experimental studies of the mechanics of such vesicles remain challenging, particularly at the nanometer scale where appropriate theoretical models have also been lacking. Here, we probe the mechanical properties of nanoscale liposomes using atomic force microscopy (AFM) indentation. The mechanical response of the nanovesicles shows initial linear behavior and subsequent flattening corresponding to inward tether formation. We derive a quantitative model, including the competing effects of internal pressure and membrane bending, that corresponds well to these experimental observations. Our results are consistent with a bending modulus of the lipid bilayer of ∼14kT. Surprisingly, we find that vesicle stiffness is pressure dominated for adherent vesicles under physiological conditions. Our experimental method and quantitative theory represents a robust approach to study the mechanics of nanoscale vesicles, which are abundant in biology, as well as being of interest for the rational design of liposomal vectors for drug delivery.
纳米囊泡（∼100nm）在细胞生物学中无处不在，是药物传递的重要载体。囊泡的力学性质已知会影响细胞摄取，但变形动力学如何影响内化的机制还知之甚少。这在一定程度上是由于对这种纳米囊泡的力学性质的实验研究仍然具有挑战性，特别是在纳米尺度下，适当的理论模型也缺乏。在这里，我们使用原子力显微镜（AFM）压痕法探测纳米脂质体的力学性能。纳米囊泡的力学响应表现出初始线性行为，随后是向内的系链形成的扁平化。我们得出了一个定量模型，包括内部压力和膜弯曲的竞争效应，该模型与这些实验观察结果非常吻合。我们的结果与脂质双层的弯曲模量∼14kT 一致。令人惊讶的是，我们发现，在生理条件下，对于附着的囊泡，囊泡的刚性由压力主导。我们的实验方法和定量理论代表了一种研究生物学中丰富的纳米囊泡力学的稳健方法，这对于合理设计用于药物传递的脂质体载体也具有重要意义。
