Glass tube

A mixture of polystyrene (PS) and poly(methyl methacrylate) (PMMA) beads (10 μm diameter, Phosphorex) was prepared by mixing microsphere solutions together with water and vortexed for 30 s. A droplet of solution was placed on a coverslip for ten minutes. The dried microsphere mixture was then sealed for imaging. For SRL spectroscopic imaging of flowing microspheres, a syringe pump (PHD2000, Harvard Apparatus) was used to pump the mixture into a glass tube (300 μm inner diameter, World Precision Instrument) at a flow speed of 1 mm/s.

Cholesteryl oleate and glyceryl trioleate were purchased from Sigma-Aldrich. Prostate cancer PC3 cells were cultured in F-12K medium (ATCC) supplemented with 10% FBS (Sigma-Aldrich) in a humidified atmosphere of 5% CO₂ at 37 °C. For the compositional analysis of lipid droplets, PC3 cells (0.3×10⁶) were seeded in glass bottom dishes (In Vitro Scientific). After overnight incubation, the media was replaced with fresh media supplemented with 10 μM avasimibe or DMSO. The cells were then cultured for 2 days. For SRL spectroscopic imaging of all-trans retinol treated cancer cells, pancreatic cancer MIA PACA-2 cells were seeded in glass-bottom dishes at a density of 10⁵ cells/ml. After overnight incubation, all-trans retinol dissolved in ethanol was added to the culture medium at final concentration of 100 μM. Equal amount of ethanol was added to the control group. Images were taken 24 hours after the treatment. For SRL spectroscopic imaging of fast flowing PC3 cells, PC3 cells (~ 1×10⁶) were harvested in 1 ml PBS prior to the experiment and then loaded by a syringe pump (PHD2000, Harvard Apparatus) into a glass tube (300 μm inner diameter, World Precision Instrument) at a speed of 0.5 mm/s.