Multi-responsive hydrogels self-assembled from methacrylated PEI: rational synthesis and applications in the biomedical field

In this work we investigate the properties and applications of the supramolecular hydrogel materials synthesized by partial methacrylation of polyethyleneimine. The methacrylated PEI (PEI-MA) molecules self-assemble in water into highly swollen hydrogels with tunable hydrophilicity and microstructure. The modified PEI-MA molecules were characterized by FTIR and NMR spectroscopy to relate the synthesis parameters to the degree of methacrylation. The hydrogel morphology and its multi-scale features arising from the supramolecular interactions among the PEI-MA macromolecules were analyzed by small-angle X-ray scattering and by confocal laser scanning microscopy, which enabled to visualize the interconnected micro-cavities of the network in water. The PEI-MA hydrogels show multi-responsive properties and can be used as enabling platform for relevant applications in the biomedical and biotechnology fields. First, they are activated under multi-photon near-infrared laser irradiation in the presence of molecular probes with free carboxylic acid groups or hydroxyl groups, including cell-active probes such as RGD. At the same time, due to their polycationic nature and responsiveness to pH changes, these hydrogels can be used as platforms for the reversible binding and pH-induced release of plasmid DNA.