U. Wojda et al., Surface membrane biotinylation efficiently mediates the endocytosis of avidin bioconjugates into nucleated cells, BIOCONJ CHE, 10(6), 1999, pp. 1044-1050
Here we demonstrate that biotin covalently attached to cell surface obligat
es existing receptors to endocytose avidin bioconjugates into nucleated cel
ls. Incubation of fluorescein-labeled avidin with biotinylated cell lines r
esulted in uniform and rapid surface attachment and endocytosis compared wi
th no detectable association of the avidin-conjugated dye with unbiotinylat
ed cells. Uptake was detected within minutes with efficiencies approaching
100% in cell Lines and freshly obtained peripheral blood mononuclear cells.
After 24 h, avidin was barely detectable on the surface of the nucleated c
ells. In marked contrast, fluorescent avidin remained exclusively on the ex
ternal membrane of erythrocytes after 24 h. To investigate biotin mediated
endocytosis for the delivery of DNA, we prepared polyethylenimine-avidin (P
EI-avidin) conjugates. Surface biotinylation significantly increased the tr
ansfection efficiencies of PEI-avidin condensed plasmid DNA coding green fl
uorescent protein (GFP) to the level of transferrin-receptor targeted gene
delivery (15-20% GFP positive cells in culture after 48 h). The increase in
transfection efficiency was blocked by the addition of free avidin or biot
in to the culture medium. Biotin covalently bound to cell surface membrane
proteins efficiently mediates the entry of avidin bioconjugates into nuclea
ted cells.