Figure 7.

(a) Chemical structure of the BMAAD polymer and Cryo-TEM images of the formed micelles with charge-conversion at different pH (reproduced with permission from reference 69, Copyright 2013 American Chemical Society); (b) Synthesis of PAD polymer and charge-shifting mechanism through hydrolysis that facilitated the release of nucleic acid (reproduced with permission from reference 70, Copyright 2020 American Chemical Society); (c) Propionic 4-acetoxybenzyl ester modified PEI reversed cationic charge via esterase-mediated hydrolysis to form a zwitterionic species (reproduced with permission from reference 72, Copyright 2016 Wiley-VCH Verlag GmbH & Co).