“…With an excellent biocompatibility [23][24][25][26][27][28][29][30][31][32][33][34][35] and responsiveness to external stimuli, including enzymes, 23,24 pH, 25,26 and reactive oxygen species, 27 polypeptides have been used in various elds, including the biomedical eld, as drug delivery systems 23,27,29 and hydrogels. 24,[27][28][29] For example, poly-L-lysine (PLL), which is traditionally used as a coating agent for culture media to enhance the attachment of cells 30 and manipulate neuronal cellular fate, 31 has a primary amino group in its side chain, which contributes to structural changes associated with pH changes.…”