Lipid staining

To examine the lipoprotein particles, a fluorescent neutral lipid dye 4,4-difluoro-1,3,5,7,8-pentamethyl-4-bora-3a,4a-diaza-s-indacene (BODIPY 493/503, Thermo Fisher Scientific, USA) was used. The BODIPY was dissolved into PBS at 1 mg ml⁻¹, followed by mixing vigorously to mechanically emulsify this solution. Then, 20 μl BODIPY solution was mixed with a 20 μl sample and incubated for 15 min in a dark environment. After that, the mixture was dropped onto Shandon^™ Double Cytoslides^™ (Thermal Fisher Scientific, USA) and incubated for 5 min. Next, the slide was washed 3 times with PBS. A cover slide (VWR, USA) was placed on the sample and observed under a fluorescent microscope.