A mechanically strong conductive hydrogel reinforced by diaminotriazine hydrogen bonding

Stiff micelle-crosslinked hyaluronate hydrogels with low swelling for potential cartilage repair

Pluronic F127 diacrylate (F127DA) nano-micelle crosslinked methacrylated hyaluronic acid (MeHA) hydrogels (NMgels) with strong compressive properties have been demonstrated in our previous study. The current study further focuses on how the F127DA micelles and long-term swelling affect the mechanical performance of hydrogels from the view of in vitro/in vivo applications. Co-contributions of the F127DA micelles and MeHA to the compression performance are first investigated through mechanical analysis and cyclic loading/unloading tests before and after swelling. The optimized NMgel with F127DA micelles of 15 wt% and MeHA of 1.5 wt% (F15H1.5) exhibits a low swelling ratio and a well-maintained network in pH = 7.4 phosphate buffered saline. The abundant hydration significantly affects the initial mechanical properties of the hydrogels. After swelling, the compressive strength, modulus and fracture energy of F15H1.5 NMgel decrease from ∼3.44 MPa, ∼312 kPa and ∼407.5 kJ m-3 to 0.59 MPa, ∼55 kPa, and ∼81.8 kJ m-3, respectively. The energy dissipation of the first loading-unloading cycle dramatically decreases from ∼21.5 kJ m-3 to ∼6.0 kJ m-3 as well. Nevertheless, the gel still retains excellent stiffness, toughness and self-recovery due to the dense and strong micelle linkages. In vivo studies show that the implantation of F15H1.5 hydrogel in thyroid cartilage defects of rabbit larynx effectively promotes the regeneration of cartilage after 8 weeks. These results indicate that the stiff NMgel is a promising cartilage tissue engineering scaffold for the regeneration of cartilage in vivo.

Poly(vinyl diaminotriazine): From Molecular Recognition to High-Strength Hydrogels

Poly(2-vinyl-4,6-diamino-1,3,5-triazine), (PVDT) with diaminotriazine residues is found to form not only intramolecular hydrogen bonds, but also three robust, complementary hydrogen bonds with nucleobases such as thymine and uracil. Taking advantage of the three complementary hydrogen bonds, molecular recognition of a nucleic acid base has been investigated in previous work. Over the past few years, the use of PVDT has been extended to the construction of gene delivery vectors and nonswellable, high-strength hydrogels by copolymerization with a hydrophilic monomer and/or crosslinker. In particular, many fascinating properties, such as excellent mechanical properties, stimuli responsiveness, the shape memory effect, and biodegradability, have emerged in PVDT-based hydrogels. In this article, the molecular recognition and self-assembly of diaminotriazine are introduced first, and then a particular focus is placed on the development of PVDT-based high performance hydrogels, especially their biorelated applications.