Sizing lipid droplets from adult and geriatric mouse liver tissue via nanoparticle tracking analysis

The significance of lipid droplets in lipid metabolism, cell signaling, and regulating longevity is increasingly recognized, yet the lipid droplet's unique properties and architecture make it difficult to size and study using conventional methods. To begin to address this issue, we demonstrate the capabilities of nanoparticle tracking analysis (NTA) for sizing of lipid droplets. NTA was found to be adequate to assess lipid droplet stability over time, indicating that lipid droplet preparations are stable for up to 24 h. NTA had the ability to compare the size distributions of lipid droplets from adult and geriatric mouse liver tissue, suggesting an age-related decrease in lipid droplet size. This is the first report on the use of NTA to size intracellular organelles. Graphical Abstract Light scattering reveals the temporal positions of individual lipid droplets, which are recorded with a camera. The two-dimensional diffusion constant of each lipid droplet is extracted from the data set, which is then used to calculate a hydrodynamic radius using the Stokes-Einstein equation.