Easy and Fast Preparation of Large and Giant Vesicles from Highly Confined Thin Lipid Films Deposited at the Air–Water Interface

Abstract

Lipid vesicles are supramolecular structures of great interest for industrial and research applications. They can be used simply to compartmentalize solutions and pack active molecules in femtoliter-scale volumes or as highly sophisticated drug delivery vehicles and dynamic cell-size bioreactors. For these reasons, many methods for the production of vesicles have been developed, and some of them present several drawbacks, such as long working times and the requirement of specific equipment to perform the technique. In this work, we present a method to produce vesicles from highly confined lipid films at the air–water interface. The procedure involves two simple steps: the formation of the thin lipid film at the air–water interface and then brief sonication (10 s). These films are obtained by depositing different aliquots of lipid organic solutions at the air–liquid interface of round-bottom Eppendorfs tubes. The morphology of the highly confined lipid thin films was studied by optical microscopy noting the formation of non-uniform depositions at the air–liquid interface, with the presence of thicker portions close to the container sidewall. Post-sonication, the presence of vesicles composed of 2-oleoyl-1-palmitoyl-sn-glycero-3-phosphocholine (POPC) or 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC) was confirmed using the complementary techniques of fluorescence microscopy and flow cytometry. The size distribution investigations carried out by flow cytometry revealed the optimal concentrations to favor the formation of giant vesicles (GVs). Furthermore, we investigated aqueous phase encapsulation by adding calcein or green fluorescent protein (GFP) to the aqueous phase then characterized by fluorescence microscopy and flow cytometry. We demonstrate a fast and easy method for producing vesicles including GVs on demand.