Lipid bilayers on a picoliter microdroplet array for rapid fluorescence detection of membrane transport

This paper describes picoliter-sized lipid bilayer chambers and their theoretical model for the rapid detection of membrane transport. To prepare the chambers, semispherical aqueous droplets are patterned on a hydrophilic/hydrophobic substrate and then brought into contact with another aqueous droplet in lipid-dispersed organic solvent, resulting in the formation of the lipid bilayers on the semispherical droplets. The proposed method implements the lipid bilayer chambers with 25-fold higher ratio of lipid membrane area (S) to chamber volume (V) compared to the previous spherical droplet chambers. Using these chambers, we are able to trace the time-course of Ca(2+) influx through α-hemolysin pores by a fluorescent indicator. Moreover, we confirm that the detection time of the substrate transport is inversely proportional to the S/V ratio of the developed chambers, which is consistent with the simulation results based on the developed model. Our chambers and model might be useful for rapid functional analyses of membrane transport phenomena.