Microfluidic System for Continuous Triacylglycerol Supply with Ethanol as a Cosolvent to Artificial Organelle Models

Recent studies have focused on incorporating functional molecules into liposomes, which can serve as models for artificial cells and organelles. Artificial cells have certain cellular functions, such as the replication of genetic material and protein synthesis, whereas artificial organelles mimic specific organelle functions, including those of mitochondria and lysosomes. Sustained functioning of these systems requires a continuous supply of substrates. The mechanism of formation of lipid droplets is not yet fully understood despite their involvement in metabolic disorders such as obesity and nonalcoholic fatty liver disease. Artificial organelle systems offer a promising platform for elucidating the mechanism of lipid droplet formation. To establish an artificial lipid droplet preparation system, continuous delivery of triacylglycerol─a water-insoluble compound─is essential. In this study, triacylglycerol was solubilized in an aqueous solution using ethanol (EtOH) as a cosolvent and then supplied via a microtube pump system to giant unilamellar vesicles (GUVs) functioning as artificial endoplasmic reticulum. Large unilamellar vesicles (LUVs) were used to assess the effects of EtOH. LUVs retained their vesicular structure in 30 wt % EtOH solution, although EtOH altered membrane properties, such as mobility of phospholipids and hydrophobicity of the liposomal membranes. Similarly, GUVs maintained their structural integrity under the conditions of continuous supply with triacylglycerol via the microtube pump system. Thus, the flow system provides a promising platform for artificial lipid droplet preparation.