Investigation of interfacial organization of nanoscopic species at flowing liquid crystal-water interfaces

Date

2025-9

Author

Dedeoğlu, Cansu

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Cell membranes are composed primarily of phospholipid bilayers that are critical for maintaining cellular activities, and alterations contribute to diseases, such as Alzheimer's and neurodegenerative disorders. While previous studies have shown that phospholipids at static nematic liquid crystal (LC)-water interfaces induce interface-driven orientational transitions, precise quantification of vesicle fusion kinetics, influenced by the mechanical properties, remains limited. In this study, we introduce a novel microfluidic platform forming a flowing soft interface of nematic LC-aqueous phases, enabling continuous and rapid quantification due to the high responsiveness of LC interfaces. We investigated phospholipids with varying mechanical properties: 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC, Tm= 2°C), 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC, Tm= -17 °C), (liquid-like) 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC, Tm= 41°C), sphingomyelin (Egg SM, Tm=38°C), (solid-like). Using fluorescence and polarized light microscopy, we found that lipid-rich domains accumulated at the end of the channel due to advection-dominated flow, determined by fusion kinetics. We revealed that DLPC and DOPC showed similar fusion kinetics, while Egg SM vesicles failed to fuse into the interface due to their rigid nature, unlike DPPC, which underwent shear induced fusion of vesicles to the interface. Moreover, we showed the effect of softening (via DTAB) and stiffening (via C16-ceramide) on vesicles. DTAB-lipid mixed micelles showed high coverage at the interface, including for rigid Egg SM. In contrast, C16-ceramide-doped DLPC vesicles did not fuse, indicating enhanced rigidity. Cholesterol exhibited lipid-specific effects: it increased the rigidity of DLPC and DOPC vesicles up to ~50 mol%, gradually stiffened DPPC, and softened Egg SM at 75% cholesterol, enabling shear-induced fusion of vesicles to the interface. These findings provide new insights into changing membrane mechanics with changing compositions of guest molecules and propose a platform for early diagnosis of membrane mechanics-associated diseases.

Subject Keywords

Microfluidics, Adsorption, Liquid crystals, Aqueous interfaces, Lipid vesicles

URI

https://hdl.handle.net/11511/115636

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Graduate School of Natural and Applied Sciences, Thesis