Yahyazadeh Shourabi Arash, Kieffer Roland, de Jong Djanick, Tam Daniel, Aubin-Tam Marie-Eve
Department of Bionanoscience, Kavli institute of Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ, Delft, The Netherlands.
Laboratory for Aero and Hydrodynamics, Faculty of Mechanical Engineering, Delft University of Technology, 2628 CD, Delft, The Netherlands.
Soft Matter. 2024 Oct 30;20(42):8524-8537. doi: 10.1039/d4sm00706a.
Coexistence of lipid domains in cell membranes is associated with vital biological processes. Here, we investigate two such membranes: a multi-component membrane composed of DOPC and DPPC lipids with gel and fluid separated domains, and a single component membrane composed of PMPC lipids forming ripples. We characterize their mechanical properties below their melting point, where ordered and disordered regions coexist, and above their melting point, where they are in fluid phase. To conduct these inquiries, we create lipid bilayers in a microfluidic chip interfaced with a heating system and optical tweezers. The chip features a bubble trap and enables high-throughput formation of planar bilayers. Optical tweezers experiments reveal interfacial hydrodynamics (fluid-slip) and elastic properties (membrane tension and bending rigidity) at various temperatures. For PMPC bilayers, we demonstrate a higher fluid slip at the interface in the fluid-phase compared to the ripple phase, while for the DOPC:DPPC mixture, similar fluid slip is measured below and above the transition point. Membrane tension for both compositions increases after thermal fluidization. Bending rigidity is also measured using the forces required to extend a lipid nanotube pushed out of the freestanding membranes. This novel temperature-controlled microfluidic platform opens numerous possibilities for thermomechanical studies on freestanding planar membranes.
细胞膜中脂质域的共存与重要的生物过程相关。在此，我们研究两种这样的膜：一种由DOPC和DPPC脂质组成的多组分膜，具有凝胶相和液相分离的区域；另一种由PMPC脂质组成的单组分膜，形成波纹。我们表征了它们在熔点以下（有序和无序区域共存）以及熔点以上（处于液相）的力学性能。为了进行这些研究，我们在与加热系统和光镊相连的微流控芯片中创建脂质双层。该芯片具有气泡捕获功能，并能够高通量形成平面双层。光镊实验揭示了在不同温度下的界面流体动力学（流体滑移）和弹性特性（膜张力和弯曲刚度）。对于PMPC双层，我们证明在液相中界面处的流体滑移比波纹相时更高，而对于DOPC:DPPC混合物，在转变点以下和以上测量到类似的流体滑移。两种组成的膜在热流化后膜张力都会增加。弯曲刚度也通过将从自由站立膜中推出的脂质纳米管拉伸所需的力来测量。这种新型的温度控制微流控平台为自由站立平面膜的热机械研究开辟了众多可能性。
