Reversible swelling behaviour of Diels–Alder clicked chitosan hydrogels in response to pH changes

Abstract

Poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide) (PPO-PEO-PPO) based bismaleimide (BMI) was employed as cross-linking agent for the synthesis of pH-sensitive clicked hydrogels by Diels-Alder (DA) reaction with furan-grafted chitosan in aqueous solution. The effect of the surrounding pH over the microstructure and the swelling ability of the hydrogels was evaluated depending on the initial composition. The results suggested that the hydrogels maintained the characteristic responsive properties of the original biopolymer even after the cross-linking reaction. The different macromolecular networks remarkably affected the final properties, especially when referring to pH-swelling sensitiveness and hydrogel porosity. In addition, the swelling parameters revealed that the hydrogels presented large liquid absorption capacity, showing excellent recovery properties and responsiveness at different pHs. The promising features of the ensuing hydrogels made them suitable as targeted pH-sensitive drug delivery systems.

Carbon Dot Cross-Linked Gelatin Nanocomposite Hydrogel for pH-Sensing and pH-Responsive Drug Delivery

“…A single phase was found for the GNC0 hydrogel (Figure S2A, SI), which changes into two distinct phases on increasing the CD percentages in the gelatin matrix. Moreover, the smooth gelatin hydrogel surface (as shown in Figure S2B, SI) becomes rough due to the favorable covalent interaction between CDs and the gelatin matrix 28 (Figure S2D,F, SI). The roughness profile is described in terms of average roughness ("Sa") and root-mean-square roughness ("Sq") in Table S2 (SI).…”

Diels–Alder Cycloaddition Reactions in Sustainable Media

“…Gabilondo's group reported the synthesis of several biocompatible hydrogels by the Diels-Alder click cross-linking reaction between functionalized furans and maleimides in water, namely methacrylate-based hydrogels [133], methacrylate/polyetheramine [134] and starch/graphene crosslinked hydrogels [135], chitosan-based hydrogels [136] and starch-based nanocomposite hydrogels [137]. The starch-based nanocomposite hydrogels were prepared through the Diels-Alder click reaction between a furan-functionalized starch derivative 211 and a water-soluble PEG-based tetramaleimide 212, followed by the addition of cellulose nanocrystals as nanoreinforcement (Scheme 49) [137].…”

Design and Synthesis of Chitosan—Gelatin Hybrid Hydrogels for 3D Printable in vitro Models

“…The final hybrid biomaterial shows the greatest swelling rate (1,700%) between 2 and 24 h; however, by 72 h, the swelling decreases to 800% in the absence of polymer degradation and release into the medium. These results could be related to the free functional groups of the hybrid material resulting in a different structural organization of polymer chains during water uptake (Mao et al, 2006 ; Saraiva et al, 2015 ; Li et al, 2017 ; Guaresti et al, 2019 ). The hybrid reaches swelling equilibrium at 144 h, showing adequate properties for in vitro cell studies.…”