Photoactivated Localization Microscopy, or PALM imaging, is a super-resolution technique that relies on the random activation of fluorophores to spatially resolve molecular details (Betzig et al. 2006). In brief, upon activation with the adequate laser, a sparse number of fluorophores emit for a short period before bleaching. Because fluorophores are only activated at the same time in small numbers until all have emitted, it is possible to localize and track single molecules over time.
Cells release different types of small-sized membrane vesicles (from 30nm to 1000nm) as a way of communicating with other cells and remove unwanted cell contents; these vesicles are collectively known as extracellular vesicles (EVs). Here we share how we have optimized the imaging of purified EVs to study their size, content and behavior using super-resolution microscopy.