Droplets have gathered attention as a new category of DDSs. In particular, the incorporation of immunoglobulin G (IgG), which is widely used as a component of antibody drugs, is an emerging demand. Recently, LLPS-induced IgG-FcB(L17E) condensates were proposed as a new DDS carrier of antibody drugs to increase cytosolic delivery activity. To evaluate the applicability of our phase-diagrambased droplet design in medicine, we prepared IgG droplets by adding an IgG solution to the PLL/ATP mixture and monitored the formation of IgG droplets, dispersions, or aggregates (Figure , Figure ). After mixing ATP and PLL solutions, we added and mixed a 1/10 volume of a 100 mg/mL IgG solution containing ca. 1% of rhodamine-labeled fluorescent IgG for observation.