Mechanical Characterization of Liposomes and Extracellular Vesicles, a Protocol

Daan Vorselen; Melissa C Piontek; Wouter H Roos; Gijs J L Wuite

doi:10.3389/fmolb.2020.00139

Mechanical Characterization of Liposomes and Extracellular Vesicles, a Protocol

Front Mol Biosci. 2020 Jul 21:7:139. doi: 10.3389/fmolb.2020.00139. eCollection 2020.

Authors

Daan Vorselen¹, Melissa C Piontek², Wouter H Roos², Gijs J L Wuite¹

Affiliations

¹ Fysica Van Levende Systemen and LaserLab, Vrije Universiteit Amsterdam, Amsterdam, Netherlands.
² Moleculaire Biofysica, Zernike Instituut, Rijksuniversiteit Groningen, Groningen, Netherlands.

Abstract

Both natural as well as artificial vesicles are of tremendous interest in biology and nanomedicine. Small vesicles (<200 nm) perform essential functions in cell biology and artificial vesicles (liposomes) are used as drug delivery vehicles. Atomic Force Microscopy (AFM) is a powerful technique to study the structural properties of these vesicles. AFM is a well-established technique for imaging at nanometer resolution and for mechanical measurements under physiological conditions. Here, we describe the procedure of AFM imaging and force spectroscopy on small vesicles. We discuss how to image vesicles with minimal structural disturbance, and how to analyze the data for accurate size and shape measurements. In addition, we describe the procedure for performing nanoindentations on vesicles and the subsequent data analysis including mechanical models used for data interpretation.

Keywords: (small) vesicles; Canham-Helfrich theory; atomic force microscopy (AFM); bending modulus; extracellular vesicles; liposomes; mechanical properties; nanoindentation.