Stretching transition of vesicles with confined filament loops: Morphological evolution with filament distortion and reorientation

The intricate mechanical interplay between cell membranes and enclosed filaments or filament networks plays a pivotal role in governing cellular morphological transformations and various cellular activities. A profound understanding of the fundamental mechanical mechanisms underlying these interactions can be gained by exploring the mechanical behaviors of the filament–vesicle system. Here we theoretically investigate the axial stretching of a lipid vesicle containing an enclosed filament loop. The vesicle either freely adjusts its volume or maintains a fixed volume. Depending on the relative stiffness and size of the filament loop to the vesicle as well as the vesicle scenario, the vesicle prior to stretching exhibits a spherical, prolate or oblate shape, and during stretching it undergoes morphological transformations with pronounced filament distortion and reorientation. The filament–vesicle system could exhibit a spring-softening or -stiffening response during stretching. Moreover, effects of filament inhomogeneity on the stretching process are studied. Our results could serve as a quantitative benchmark for further investigations into cellular complexity.