Zwitterionic polyaspartamides based on L-lysine side-chain moieties: Synthesis, nonfouling properties and direct/indirect nanogel preparation

The ability of polysuccinimide (PSI) to open the succinimide ring by nucleophilic reagents leads to the formation of various polyaspartamides under mild conditions. In the current work, amino acids, such as N α-Boc-L-lysine, leading to the formation of exclusively α-substituted L-lysine polypeptides and L-lysine methyl ester were used as the ring-opening reagents for PSI. The formed materials possess both positively and negatively charged groups on the same repeat unit simultaneously serving as zwitterionic moieties. The chemical structure and component composition were confirmed by 1 H NMR and UV/vis spectroscopies. Zwitterionic properties of the synthesized polymers were investigated by zeta potential measurements. The obtained zwitterionic polyaspartamides exhibited anti-protein adsorption properties and the ability to create hydrophilic surfaces. The zwitterionic polyaspartamide nanogels obtained by horseradish peroxidase-mediated crosslinking in inverse miniemulsions and applying different preparation strategies were analysed by dynamic light scattering (DLS) measurements and transmission electron microscopy (TEM) analysis. The results indicated the good morphology and architecture of the nanogels. These peptide-based zwitterionic nanogels, due to their good biocompatibility and anti-protein adsorption ability, are promising materials for biomedical applications.