FURTHER-STUDIES ON TARGETED DNA TRANSFER TO CELLS USING A HIGHLY EFFICIENT DELIVERY SYSTEM OF BIOTINYLATED TRANSFERRIN AND BIOTINYLATED POLYLYSINE COMPLEXED TO STREPTAVIDIN

Conjugates consisting of biotinylated transferrin and biotinylated pol y-L-lysine attached to streptavidin have been prepared and found to tr ansfer luciferase plasmid DNA very efficiently to HeLa cells in the pr esence of chloroquine. Transfection was dependent on (i) use of biotin ylated short chain polylysine containing 70 lysine residues, (ii) biot inylated transferrin containing 1-2 biotin moieties, (iii) reaction of biotinylated transferrin with streptavidin followed by isolation of t he resulting conjugate on Sephadex G-200 and (iv) interaction of strep tavidin-biotinylated transferrin with biotinylated polylysine giving a complex suitable for DNA transfection. It was found that if the above sequence of steps resulting in the formation of streptavidin-biotinyl ated transferrin/biotinylated polylysine was followed without isolatio n of intermediate conjugates by Sephadex G-200 chromatography, pRSVL D NA transfer was still very efficient. Transfer of luciferase DNA by th e streptavidin conjugates and subsequent expression of luciferase acti vity was almost completely inhibited by excess free transferrin, showi ng that gene transfer was through the transferrin receptor pathway via receptor-mediated endocytosis. The streptavidin (bio(2)-transferrin) bio(10)-pLys(70) conjugate used in the present experiments was approxi mately one hundred times more efficient in pRSVL DNA transfection with the HeLa cells than the previously described avidin-pLys(460) (bio-tr ansferrin) complex.