Analysis of Stiffness Measurement Methods on Extracellular Vesicles

Sammanfattning: Extracellular vesicles are important players in cell-to-cell communication and have the potential to be used as biomarkers for decease. The mechanical properties of extracellular vesicles is an active field of research, with new methods and models being developed. In this thesis, two samples of extracellular vesicles containing different levels of membrane protein expressions are investigated using atomic force microscopy. Three models for determining stiffness are applied to the samples: the Hertz model, an adhesion angle dependent model, and the modified Canham-Helfrich model. The Hertz model indicated a higher Young’s Modulus for vesicles without membrane proteins, but with large errors. The adhesion angle dependent model did not provide high enough sensitivity to determine any difference in stiffness between the two samples. The modified Canham-Helfrich model indicated a higher bending modulus for the vesicles with membrane proteins. The results highlight the importance of taking several measurements on each vesicle, in contrast to how the method is currently applied in research.