4.3. Preparation of Liposomes by Microfluidics

Liposomes were prepared using a readymade microfluidic micromixer and 3D-printed microfluidic devices (Figure 4) connected to the Dolomite Microfluidic System. The commercial cartridge is 52 mm thick and 36 mm high with molded channels 300 μm in width and 130 μm in height with a staggered herringbone structure. To note, the cartridge channels for the commercial chip are smaller (1/3) with respect to the ones manufactured by 3DP. As previously mentioned in Section 2.2, phospholipids (DMPC) combined with cholesterol at a ratio of 2:1 were dissolved in ethanol at a concentration of 1 mg/mL.

Fluids were delivered into the chip using two pressure pumps with respective fluidic connections in fluorinated ethylene propylene (PEF) of outside diameter (OD) 1/16 and inside diameter (ID) 250 μm. Flow rate ratio and TFR were controlled using two Mitos Flow Rate Sensors (0.2–5 mL min⁻¹). The two chip inlets correspond to the lipid solution and the aqueous solution (PBS, pH 7.4). The liposome batch suspensions were collected from the outlet port, centrifuged at 14,800 rpm for 30 min in order to separate them from the supernatant, and rinsed three times with 1 mL of PBS in order to eliminate the organic solvent.