Multicellular spheroids are three-dimensional in vitro models of organs and tissues. Multicellular spheroids have gained great interest in the fi eld of biotechnology as they are reproducible and mimic real organs and tissues so can be used as test systems for new forms of drugs, allowing minimizing the use of in vivo animal models. Flow cytometry was used to describe the accumulation of submicron polymeric microcapsules in cellular spheroids, which allowed us to identify the main aspects of drug carrier-cell interactions within the spheroid.
