Novel transfecting assemblies comprising biotinylated cationic
liposomes,
DNA and tribiotinylated
transferrin-
streptavidin (streptavidin(bio3-transferrin)) accessories have been prepared, characterized and evaluated for toxicity and
DNA delivery capability in human cervical
carcinoma cells (HeLa). Two new lipophilic cholesteryl-based
biotin derivatives, biotinylcholesterylformylhydrazide (MSB1) and aminohexanoylbiotinylcholesterylformylhydrazide (MSB2) provided docking points for streptavidin(bio3-transferrin) on cationic
liposomes which were formulated with N,N-dimethylaminopropylaminylsuccinylcholesterylformylhydrazide (MS09) and
dioleoylphosphatidylethanolamine (DOPE) in a 2:48:50 molar ratio.
Ethidium dye displacement assays and gel retardation studies suggest that in ternary complexes, the
DNA is electrostatically bound to the cationic
liposomes while
transferrins remain
liposome-bound through
streptavidin-
biotin interactions. Assemblies fully protected plasmid
DNA from serum nuclease digestion over a range of
liposome:pGL3
DNA ratios (3-8:1, w/w) and exhibited low growth inhibition of HeLa cells (circa 5%) at the optimal transfection composition for
streptavidin(bio3-
transferrin):
liposome:pGL3
DNA of 10:6:1 (w/w/w). Transfection levels, which were twice those of untargeted lipoplexes containing MSB1 or MSB2, were not significantly diminished in the presence of 10% foetal bovine serum. Excess
transferrin (200 microg per well) reduced transfection levels to those of untargeted complexes, supporting the notion that at least 50% of ternary complexes gained entry into the cervical
carcinoma cells by receptor mediation. Conversely, transfection levels with untargeted lipoplexes were only slightly reduced in the presence of
transferrin at the same concentration.