Nuclepore track etched polycarbonate membrane filter

DMPC powder (850345P) and DOPE-PEG(2000)-N-Cy5 chloroform solution (880153C) were purchased from Avanti Polar Lipids (Alabaster, AL, USA); 70 nm and 250 nm liposome stock solutions (1 mg/mL) were produced by first dissolving DMPC in chloroform (Fisher Chemical, Waltham, MA, USA, C298-500) and then adding DOPE-PEG(2000)-N-Cy5 (99.9:0.1-DMPC:DOPE-PEG(2000)-N-Cy5) for future fluorescent visualization. The lipids were desiccated overnight in a vacuum chamber to form a lipid film. The next day, the lipids were dissolved in PBS (Gibco, 70011-044) and strongly vortexed. The lipid solution was then extruded through an Avanti Mini-Extruder (610000-1EA); 70 nm liposomes were passed through a 0.2 μm Nuclepore track-etched polycarbonate membrane filter (Whatman, Maidstone, UK, 800281), followed by a 0.05 nm filter (800308); 250 nm liposomes were passed through a 0.4 μm filter (800282) and then a 0.2 μm filter; 10 mm filter supports were used (Avanti Polar Lipids, 610014-1Ea). The size of the liposomes (Table S1) was confirmed by dynamic light scattering (DLS) using a Zetasizer NanoSampler (Malvern, UK), and they were stored at 4 °C until further use.