Sustainable Electro-Responsive Semi-Interpenetrating Starch/Ionic Liquid Copolymer Networks for the Controlled Sorption/Release of Biomolecules

The main objective of this work was the development and characterization of sustainable electro-responsive ionic liquid-based cationic copolymers. For this purpose degradable semi-interpenetrating polymer networks (s-IPNs) based on starch and on ion-conducting cationic copolymers of 2-hydroxyethyl methacrylate (HEMA) and 1-butyl-3-vinylimidazolium chloride (BVImCl), cross-linked with N,N′-methylenebis(acrylamide) (MBA), were synthesized by following principles of green chemistry. Cross-linked poly(HEMA-co-BVImCl) copolymers were also prepared for comparison. The resulting cationic hydrogels (copolymer and s-IPNs) were characterized in terms of their physicochemical, thermomechanical, morphological, and electrochemical properties, as well as in terms of cell viability and proliferation against fibroblast cells. Furthermore, the electro-assisted sorption/release capacity of the prepared hydrogels toward l-tryptophan (used as a model biomolecule) was also studied at different applied DC voltages (0, 2, 5, and 100 V). Results demonstrated that the properties of the synthesized hydrogels can be tuned, depending on their relative chemical composition, presenting electronic conductivity and ionic conductivity values in the 0.1 to 5.2 S cm–1 range, and complex shear modulus in the 0.6 to 6.4 MPa range. The sorption/release capacity of the s-IPNs after 3 h at 25 °C can also be modulated between 2.5 and 70% and 4.5 and 40%, depending on the applied DC voltage and/or sorption/release medium. Finally, none of the synthesized cationic hydrogels induced fibroblast cells lysis, although s-IPNs had a lower impact on cell proliferation than poly(HEMA-co-BVImCl) copolymers, indicating a favorable effect of starch on the biocompatibility of the synthesized s-IPNs. The designed cationic hydrogels could be useful for the development of efficient, stable, degradable and cheaper soft and multiresponsive platforms with potential applications in bioseparation processes, wastewater treatment systems (e.g., pharmaceutical), biomedical devices (e.g., sustained delivery of specific charged-biomolecules), and nonleaching electrochemical devices.