Low molecular weight hydrogels constructed from small molecule gelators have shown great promise in cell culture, tissue engineering, and controlled drug release due to the advantages such as facile construction, availability for bioresponsiveness and predictable degradation. The gelators self-assemble into fibrous nanostructures via noncovalent forces,followed by nucleation of fiber growth and gelation. Recently, the researchers from South China University of Technology reported a class of all-small-molecule dynamic covalent hydrogels via formaldehyde condensation with aminoglycosides.
Aminoglycosides are a class of naturally occurring antibiotics. The saccharide units in aminoglycosides render the molecules with excellent aqueous solubility and secondary crosslinking via hydrogen bonding interactions, while the primary amines provide a perfect reactive site to construct reversible covalent networks. Both the interactions contribute to the gel formation. The aminoglycoside hydrogels show excellent pH- and temperature-responsiveness and display controllable stiffness in the presence of different alkali cations and halogen anions.This work has been published in Materials Chemistry Frontiers.
Figure 1. (A) Synthesis of all-small-molecule dynamic covalent hydrogels. (B) Preparation of hydrogels by the proposed reactions. (C) Time-dependent rheology of the hydrogel. (D) Effect of shear rate on gel viscosity. (E) Photograph of the hydrogel ejected from a syringe. (F) Coating of the hydrogel on a paper printed with the sign of Advanced Institute for Soft Matter Science and Technology (AISMST). (G) Hydrogels loaded with methylene blue were fabricated into different shapes.
Figure 2. (A) Mechanism of temperature- and pH-responsiveness. (B) Temperature-dependent gel rheology. (C) G’ and G’’ measured at a continuous step temperature between 25 oC and 65 oC. (D) Gel degradation at various temperatures. (E) Gel degradation at various pH.
Figure 3. (A) G’ of hydrogels in the presence of 20 mM LiCl, NaCl, KCl and RbCl, respectively. (B) G’ of gels in the presence of 20 mM NaF, NaCl, NaBr and NaI, respectively. (C) Temperature-dependent gel rheology in the presence of different salts. (D) Time-dependent G’ and G’’ in the presence of 20 mM LiI.
Figure 4. (A) Time-dependent rheology of the neomycin/formaldehyde hydrogel. (B) G’ and G’’ of the hydrogel measured at a continuous step temperature between 25 oC and 65 oC. (C) Degradation of the hydrogel at pH 7.4 and 1.0, respectively. (D) Time-dependent gel rheology in the presence of 20 mM LiI.
Hui Wang, Yiyun Cheng*. All-small-molecule dynamic covalent hydrogels with multistimuli responsiveness, Materials Chemistry Frontiers, 2019, 3, 472-475.
Article link: http://dx.doi.org/10.1039/C8QM00612A