UCLA

Extracellular vesicles (EVs) are a class of lipid bilayer enclosed particles secreted by most mammalian cells, and are found ubiquitously in body fluids such as plasma and cerebrospinal fluid. EVs contain molecular signatures of their secreting host cells, and are involved in long-range intercellular communication and transfer of biomolecular cargo. There is significant potential for EVs to be used as biomarkers for specific cancers, and their involvement in long-range intercellular communication holds promise for their use as targeted drug delivery vehicles. However, EVs’ nanoscale size and heterogeneity (30-1000 nm) and the choice of isolation methods confound the structural, biophysical, and surface biochemical analysis of single vesicles. Here, we focus on the characterization of single small extracellular vesicle (sEV) (40-160 nm) structural-mechanical properties by atomic force microscopy (AFM) and other methods. We examined the impact of isolation methods on the biophysical heterogeneity of single sEVs, including their nanoscale morphology and the presence of co-isolates. We also investigated the structural-mechanical properties of breast cancer cell line-derived sEVs and their secreting cells, finding that breast-cancer derived sEVs reflect the biomechanical signature of the cancer cells that secrete them, and identify similar trends in patient plasma derived EV like particles. Finally, we demonstrated the applicability of AFM-based single sEV analysis as an efficient tool to quantify the abundance, structure, and biomechanical properties of sEVs from limited volume patient cerebrospinal fluid. Overall, this work advances the understanding of single sEV structural-mechanical properties, provides a framework to assess sEV quality and purity, and further develops cellular and nanoscale mechanotyping methodologies.