Lipoprotein particles exhibit distinct mechanical properties

Abstract

Lipoproteins (LPs) are micelle-like structures with a similar size to extracellular vesicles (EVs) and are therefore often co-isolated, as intensively discussed within the EV community. LPs from human blood plasma are of particular interest as they are responsible for the deposition of cholesterol ester and other fats in the artery, causing lesions, and eventually atherosclerosis. Plasma lipoproteins can be divided according to their size, density and composition into chylomicrons (CM), very-low-density lipoproteins (VLDL), low-density lipoproteins (LDL) and high-density lipoproteins (HDL). Here, we use atomic force microscopy for mechanical characterization of LPs. We show that the nanoindentation approach used for EV analysis can also be used to characterize LPs, revealing specific differences between some of the particles. Comparing LPs with each other, LDL exhibit a higher bending modulus as compared to CM and VLDL, which is likely related to differences in cholesterol and apolipoproteins. Furthermore, CM typically collapse on the surface after indentation and HDL exhibit a very low height after surface adhesion both being indications for the presence of LPs in an EV sample. Our analysis provides new systematic insights into the mechanical characteristics of LPs. K E Y WO R D S atomic force microscopy (AFM), chylomicrons (CM), high-density lipoproteins (HDL), lipoproteins (LPs), low-density lipoproteins (LDL), mechanical properties, very-low-density lipoproteins (VLDL) This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

Engineering a tunable micropattern‐array assay to sort single extracellular vesicles and particles to detect RNA and protein in situ

“…Atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) are often utilized to provide morphological and mechanical properties of siEVs while surpassing the optical limit of diffraction (Noble et al., 2020 ; Pascucci & Scattini, 2021 ; Ridolfi et al., 2020 ; Yurtsever et al., 2021 ). Although some distinguishing characteristics amongst the siEVPs are present, physically similar siEVPs are often undiscernible, and results are user‐dependent (Karttunen et al., 2018 ; Piontek & Roos, 2022 ; Rikkert et al., 2019 ; Zhang et al., 2011 ). Incorporating immunogold labeling with TEM can provide additional phenotyping of siEVP surface proteins, but the technique is low throughput, labor intensive, and rarely quantitative (Erdbrügger & Lannigan, 2016 ).…”

Particle profiling of EV‐lipoprotein mixtures by AFM nanomechanical imaging

“…To date, single‐particle nanomechanical studies on LPs (Bairamukov et al., 2022 ; Gan et al., 2015 ; Piontek 2022 ; Plochberger et al., 2017 ) remain sparse, with no clear consensus on the most appropriate mechanical model to apply. Some of them are based on theoretical frameworks such as Derjaguin–Muller–Toporov or Hertzian contact mechanics, whose applicability to the mechanical behaviour of pressurised vessels is questionable.…”

“…We recently implemented a single‐particle nanomechanical screening based on quantitative AFM morphometry which considerably increases analytical throughput (Ridolfi, Brucale, et al., 2020 ), making it possible to rapidly detect co‐isolated, non‐vesicular contaminants (Ridolfi, Brucale, et al., 2020 ; Ridolfi, Caselli, et al., 2020 ) and to give an estimate of their abundance relative to that of EVs (Borup et al., 2022 ). Conversely, the nanomechanical behaviour of LPs is still sparsely characterised, the first studies having appeared only very recently (Bairamukov et al., 2022 ; Piontek 2022 ; Plochberger et al., 2017 ).…”