Generation of artificial liposome using formation of double emulsion in microfluidic device

Abstract

It has been well known difficult to make phospholipid liposomes with high encapsulation efficiency, high size-uniformity, and robust formation using typical liposome production methods. The aim of this study is to make double emulsions and convert them into artificial liposomes by using a microfluidic device. We fabricated a PDMS microfluidic device which is capable of making W/O/W(water/oil/water) emulsions with high encapsulation efficiency and uniform size distribution. For successful liposome generation, hydrophilic and hydrophobic patterning in a microfluidic device is important. We used a technique for partial surface modification using oil coating to implement different hydrophilic and hydrophobic regions between two cross-junctions of the microfluidic device. We also considered the capillary number and found tolerable ranges to find the suitable zones for making double emulsions in dripping regime. After making W/O/W emulsions, we successfully converted double emulsions into artificial liposomes using solvent extraction. We evaluated the stability of generated artificial liposomes using comparisons between phase-contrast and fluorescence images over 24 hours. We confirmed that over 75% of artificial liposomes using phospholipids from soybean remained stable after 24 hours. In case of using mixed phospholipids from soybean and rat hepatocyte, over 65% of artificial liposomes remained stable after 24 hours, which means it is possible to make artificial liposomes with specific proteins and receptors. Our study can be used for safe encapsulation of specific biological materials with selected membranes.