  We report efforts to quantify the loading of cell-sized lipid vesicles using
in-line digital holographic microscopy. This method does not require
fluorescent reporters, fluorescent tracers, or radioactive tracers. A
single-color LED light source takes the place of conventional illumination to
generate holograms rather than bright field images. By modelling the vesicle's
scattering in a microscope with a Lorenz-Mie light scattering model, and
comparing the results to data holograms, we are able to measure the vesicle's
refractive index and thus loading. Performing the same comparison for bulk
light scattering measurements enables retrieval of vesicle loading for
nanoscale vesicles.
