Adipose-derived stem cells (ASCs) are multipotent cells that are emerging as an extremely promising therapeutic agent for tissue regeneration. The ability to manipulate ASC phenotypes by the delivery of biologically active cargoes is essential to understand their role and to design novel therapeutic strategies based on the use of ASCs. Here we describe a simple and efficient protocol for the conjugation and efficient delivery of biological materials into ASCs based on the use of polystyrene nanoparticles as carrier system.