Water-soluble poly(l -serine)s with elongated and charged side-chains: Synthesis, conformations, and cell-penetrating properties

Water-soluble poly(l-serine)s bearing long side-chain with terminal charge groups were synthesized via ring-opening polymerization of O-pentenyl-l-serine N-carboxyanhydride followed by thiol-ene reactions. These side-chain modified poly(l-serine)s adopt β-sheet conformation in aqueous solution with excellent stability against changes in pH and temperature. These water-soluble poly(l-serine) derivatives with charged side-chain functional groups and stable β-sheet conformations showed membrane-penetrating capabilities in different cell lines with low cytotoxicity.