functionalized biocompatible nanoparticles capable of penetrating through a mammalian cell membrane and delivering intracellularly a plurality of bioactive molecules for modulating a cellular function are disclosed herein the functionalized biocompatible nanoparticles comprise : a central nanoparticle ranging in size from about 5 to about 50 nm and having a polymer coating thereon , a plurality of functional groups covalently attached to the polymer coating , wherein the plurality of bioactive molecules are attached to the plurality of the functional groups , and wherein the plurality of bioactive molecules include at least a peptide and a protein , and wherein the peptide is capable of penetrating through the mammalian cell membrane and entering into the cell , and wherein the protein is capable of providing a new functionality within the cell . the protein may be a transcription factor selected from the group consisting of oct4 , sox2 , nanog , lin28 , cmyc , and klf4 .