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We describe a method to determine membrane bending rigidity from capacitance measurements on large area, free-standing, planar, biomembranes. The bending rigidity of lipid membranes is an important biological mechanical property that is commonly optically measured in vesicles, but difficult to quantify in a planar, unsupported system. To accomplish this, we simultaneously image and apply an electric potential to free-standing, millimeter area, planar lipid bilayers composed of DOPC and DOPG phospholipids to measure the membrane Young’s (elasticity) modulus. The bilayer is then modeled as two adjacent thin elastic films to calculate bending rigidity from the electromechanical response of the membrane to the applied field. Using DOPC, we show that bending rigidities determined by this approach are in good agreement with the existing work using neutron spin echo on vesicles, atomic force spectroscopy on supported lipid bilayers, and micropipette aspiration of giant unilamellar vesicles. We study the effect of asymmetric calcium concentration on symmetric DOPC and DOPG membranes and quantify the resulting changes in bending rigidity. This platform offers the ability to create planar bilayers of controlled lipid composition and aqueous ionic environment, with the ability to asymmetrically alter both. We aim to leverage this high degree of compositional and environmental control, along with the capacity to measure physical properties, in the study of various biological processes in the future.

and biodistribution, and drug entrapment capacity. This may require lipids with different charge in the inner and outer leaflet. It is hard to achieve this using symmetric vesicles, which have the same lipid composition in their two leaflets. Asymmetric charged vesicles by starting with a liposome with the desired inner leaflet composition, and then replacing the outer leaflet lipid molecules with desired ones. Herein, we prepared different asymmetric charged liposomes using our methyl alpha cyclodextrin exchange method, and investigated their drug entrapment performance using doxorubicin, which is cationic, and nucleic acids, which are anionic. Comparing the results with those for symmetric vesicles, demonstrated that the extent of drug entrapment was only dependent on the lipid molecules in the inner leaflet, and is maximal when the inner leaflet and drug have opposite net charge. This means that drug delivery via asymmetric charged liposome has the potential to achieve a higher therapeutic effect with a lower dose, if lipid molecules helpful for entrapment are located in the inner leaflet, while different lipids are chosen to maximize targeting and blood circulation time are introduced into the outer leaflet.

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