We have designed biotinylated polymers as synthetic receptors that have multiple alkyl groups for endocytotic delivery of target proteins. The polymers were stably attached to a cell surface via multivalent anchoring. The presented biotin was bound to streptavidin (SA) on the cell surface, and, via an endocytotic pathway, the cell rapidly internalized the biotinylated polymer/SA complex. The cell's uptake of the complex was not inhibited by the presence of 10% fetal bovine serum, and its efficacy for the uptake of SA was the highest when compared with commercial reagents and single-anchored-type synthetic receptors. The synthetic receptor-mediated endocytosis can be used generally for other kind of protein by using SA as an adaptor molecule between a target protein and the cell-surface presented biotin.
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