Extending applications of AFM to fluidic AFM in single living cell and extracellular vesicle studies

In this article, a review of the application of atomic force microscopy (AFM) for the analyses of extracellular vesicles is presented. This information is then extended to include fluidic Atomic Force Microscopy (fluidic AFM) applications. Fluidic AFM is an offshoot of AFM that combines a microfluidic cantilever with AFM and has enabled the research community to conduct biological, pathological, and pharmacological studies on cells at the single-cell level in a liquid environment. AFM applications involving single cell and extracellular vesicle studies, colloidal force spectroscopy, and single cell adhesion measurements are discussed. In this review, new results are offered, using fluidic AFM, to illustrate (1) the speed with which sequential measurements of adhesion using coated colloid beads can be done, (2) the ability to assess lateral binding forces (LBFs) of endothelial or epithelial cells in a confluent cell monolayer in appropriate physiological environment, and (3) the ease of measurement of vertical binding force (VBFs) of intercellular adhesion between heterogeneous cells. Finally, key applications are discussed that include extracellular vesicle absorption, manipulation of a single living cell by intracellular injection, sampling of cellular fluid from a single living cell, patch clamping, and mass measurements of a single living cell.