THE CONTRIBUTION OF POLY-L-LYSINE, EPIDERMAL GROWTH-FACTOR AND STREPTAVIDIN TO EGF PLL/DNA POLYPLEX FORMATION/

High-level targeted gene delivery has been demonstrated by molecular c onjugates in vitro; however, in vivo delivery has been limited The com plexity of the resulting protein/DNA polyplex and a lack of understand ing of its formation are persistent limitations. In this report, we sh ow the effect of the DNA-binding agent poly-L-lysine (PLL), the ligand epidermal growth factor (EGF), and the coupling protein streptavidin on particle size, charge and gene delivery. Smaller (<80 nm) and more stable polyplexes were obtained with PLL1116 than with shorter version s of PLL, especially in 0.15 M NaCl. Stability was increased by adding streptavidin to the polyplex; however, EGF increased particle size (> 1000 nm) and decreased gene delivery when >300 EGF molecules per poly plex were used, indicating that a critical number of EGF molecules was needed for efficient gene delivery. The correct combination of these components resulted in the most efficient gene delivery in vitro and n ow provide for testing a more stable protein/DNA polyplex to aid in en hancing gene delivery in vivo.