Polymer-assisted assembly of giant vesicles in physiological solutions

Obtaining high yields of giant unilamellar vesicles (GUVs) in solutions of physiological ionic strengths is one of the major challenges in the use of GUVs in cell-mimicking applications. This is because the free energy cost for forming GUVs increases in solutions of high ionic strengths due increased adhesion between membranes. Gel coated glass slides used in gel-assisted assembly shows promise in assembling GUVs in salty solutions. However, only limited types of gel forming polymers are known to be effective. Extensive localized micrometer-scale dewetting of the polymer film from the substrate upon hydration results in low yields of GUVs from commonly used polymers such as agarose and polyvinyl alcohol. Furthermore, for polymers that show limited dewetting, increased temperatures, required for assembling GUVs composed of lipids with high transition temperatures, results in significant dewetting which limits the temperature at which assembly can occur. Here, we show that nanocellulose paper provides a facile means of suppressing dewetting of water-soluble polymers in the gel-assisted hydration method. With dewetting is suppressed, only low amounts of polymers are necessary to obtain high yields of GUVs. We show the significant extension of the temperature range of GUV assembly using paper supported gel-assisted hydration by assembling GUVs at high yield with raft forming mixtures that require assembly at 45 °C. Moreover, we demonstrate that using nanocellulose paper as a substrate allows the assembly of GUVs from novel polymer classes such as biocompatible hyaluronic acid and dextran. We show the usage of scaled-down nanocellulose paper for the encapsulation of complex reactions in GUVs and the large scale assembly of GUVs for prototissue applications. Using nanocellulose paper as a substrate for polymer-assisted assembly of giant vesicles opens new avenues for using GUVs for biomedical and biophysical applications.