Protocol for microfluidic-based high-precision general polarization fluorescence microscopy of lipid packing in membrane vesicles

Lipid packing plays a critical role in membrane organization and function, but its precise quantification remains challenging in fluidic environments. Here, we present a protocol to integrate confocal fluorescence generalized polarization (GP) imaging with a polydimethylsiloxane (PDMS)-based microfluidic platform. We describe steps for lipid preparation, giant unilamellar vesicle (GUV) fabrication, microfluidic trapping, and GP analysis using polarity-sensitive dyes. This protocol enables robust measurement of membrane order and is readily adaptable to diverse lipid compositions and aqueous environments.