Electrostatically directed liposome adsorption, internalization and fusion on hydrogel microparticles

Supported lipid bilayers have found a diverse range of applications in understanding membrane biophysics, biosensor development, drug screening, and drug delivery. While silica has been the most frequently used supporting material, hydrogels might act as a superior alternative not only because of their soft nature allowing better interfacing with transmembrane proteins but also their porous interior for molecular containment. Unlike silica, where neutral and even same charged liposomes can readily fuse, electrostatic attraction is crucial for liposome fusion onto hydrogels. In addition to fusion, we systematically characterized other interactions including liposome adsorption onto and diffusion into hydrogels. The fused membrane forms a continuous bilayer for the most part, which is demonstrated by the observation that the diffusion of DNA is blocked but small dyes could still enter the gel. The kinetics of liposome-gel interaction is characterized using calcein loaded liposomes, where liposome rupture is observed only when the oppositely charged gel is added. With this work, a more complete picture about the interaction between liposomes and hydrogels is obtained.