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Investigating Vesicle Behavior with Atomic Force Microscopy - Force Spectroscopy


Investigating the mechanical behavior of lipid bilayer membranes is essential to understanding important cellular processes, such as morphogenesis, motility, drug delivery, mechanotransduction, metastasis, and focal adhesion. The mechanical properties of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) vesicles grafted with different 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-poly(ethylene glycol)-2000-N-[3-(2-pyridyldithio) propionate] (DSPE-PEG-PDP) concentrations were studied using Atomic Force Microscopy-Force Spectroscopy (AFM-FS) under buffer environment. The concentration of DSPE-PEG-PDP incorporated into POPC vesicles was systematically varied from 0 mol% to 10 mol%. By increasing DSPE-PEG-PDP concentration from 0 ‒ 10 mol%, vesicle size decreases, breakthrough distance increases, breakthrough force decreases, and the Young’s modulus decreases slightly. We also observe two E values exist at 5%, suggesting the existence of two conformations. PEG-grafted vesicles are sterically stabilized due to the presence of dangling PEG chains outside the vesicle membrane. The aim of this study is to examine the relationship between vesicle rigidity and vesicle stability.

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