Multi-drug delivery system using streptavidin-transforming growth factor-alpha chimeric protein

Tissue-specific delivery of a variety of molecules has been a valuable technique for biological and medical research. Therefore, we have constructed a recombinant plasmid containing the coding regions for streptavidin core and mature human transforming growth factor-alpha (TGF-alpha). The recombinant plasmid has been expressed in Escherichia coli to produce a chimeric protein with both streptavidin and TGF-alpha activity. The streptavidin-TGF-alpha chimeric protein (ST-TGF-alpha) could efficiently transfer biotinylated beta-galactosidase into A431 cells via the epidermal growth factor receptor. More than 99% of the cells contained the enzyme transferred. Furthermore, ST-TGF-alpha complexed with biotinylated-glucose oxidase had a significant cytotoxic effect when incubated with A431 cells. These findings suggest that the ST-TGF-alpha chimeric protein could be used to deliver proteins of interest into target cells without the need for chemical linkage or genetic construction. Essentially, ST-TGF-alpha serves as a high-modular "molecular bridge" for the passage of a wide variety of effector molecules into target cells.