Effect of Nicotinic Acid Conjugated to DNA-Transfecting Complexes Targeted at the Transferrin Receptor of HeLa Cells

Abstract

A conjugate consisting of streptavidin (biotinylated transferrin)-biotinylated polylysine for DNA delivery to cells was modified by partial nicotinylation of the polylysine component of the conjugate and used for transfection studies. A conjugate of biotin10-nicotinyl60-polylysine250 containing 60 weakly basic nicotinyl (pyridine-3-carboxyl) residues was prepared. The design of the modified polylysine was directed to the possible binding of H+ ions in the endosome-lysosomal vesicles (pH 5-6) by the nicotinyl groups, thus circumventing the use of chloroquine. The results obtained, however, while showing a 5- to 6-fold increase in luciferase transfection activity still necessitated an absolute requirement for chloroquine. A further polylysine conjugate containing a larger number of nicotinyl residues, biotin10-nicotinyl120-polylysine250, also was prepared and studied. This macromolecule stimulated luciferase activity to a small extent and was also dependent on chloroquine. Smaller biotinylated polylysine100 conjugates containing nicotinyl groups were also prepared. These were biotin10-nicotinyl30-polylysine100, and biotin10-nicotinyl60-polylysine100, respectively. Both substances, however, gave opaque, hazy aqueous solutions with precipitates on standing and could not be used for further experimental work. The results indicate that the introduction of weakly basic nicotinyl (pyridine-3-carboxyl) groups onto polylysine250 give conjugates that are unable to replace the lysosomotrophic agent chloroquine in the HeLa cell sysem studied. A 5- to 6-fold increase in luciferase activity, however, was found with biotin10-nicotinyl60-polylysine250.