This review discusses the challenges faced by traditional 3D bioprinting of soft or low-viscosity bioinks and embedded bioprinting as an emerging solution. We highlight the challenges involved in this process and look forward to the prospects of this technology.

Excessive inflammation, bacterial infection, and blocked angiogenesis make diabetic wound healing challenging. Multifunctional wound dressings have several advantages in diabetic wound healing. In addition, the pH regulation of the microenvironment is shown to be a key factor that promotes skin regeneration through cellular immune regulation. However, few reports have focused on the development of functional dressings with the ability to regulate the pH microenvironment and promote diabetic wound healing. This study presents a novel approach for regulating the pH microenvironment of diabetic wound sites using a glycopeptide-based hydrogel consisting of modified hyaluronic acid and poly(6-aminocaproic acid). This hydrogel forms a network through Schiff base interactions and metal complexation, which suppresses inflammation and accelerates angiogenesis during wound healing. Hydrogels not only have adequate mechanical properties and self-healing ability but can also support tissue adhesion. They can also promote the secretion of inducible cAMP early repressor, which promotes the polarization of macrophages toward the M2 type. The in vivo results confirm that hydrogel promotes diabetic wound repair and skin regeneration by exerting rapid antiinflammatory effects and promoting angiogenesis. Therefore, this hydrogel system represents an effective strategy for treating diabetic wounds.

Although significant breakthroughs have been achieved in constructing complex tissue/organ models in vitro, the progress of 3D bioprinting has long been subjected to trade-offs between printability and biocompatibility of bioinks....

The emergence and innovation of three-dimensional (3D) bioprinting provide new development opportunities for tissue engineering and regenerative medicine. However, how to obtain bioinks with both biomimicry and manufacturability remains a great issue in 3D bioprinting. Developing intelligent responsive biomaterials is conducive to break through the current dilemma. Herein, a stepwise multi-cross-linking strategy concerning thermosensitive thiolated Pluronic F127 (PF127-SH) and hyaluronic acid methacrylate (HAMA) is proposed to achieve temperature-controlled 3D embedded bioprinting, specifically precross-linking (Michael addition reaction) at low temperatures (4− 20 °C) and subsequently self-assembly (hydrophobic interaction) in a high-temperature (30−37 °C) suspension bath as well as final photo-cross-linking (mainly thiol-ene "click" reaction). The unique stepwise cross-linking mechanism promises the thermosensitive bioink appropriate viscosity at different printing stages, making it possible to print complex structures with excellent shape fidelity and simultaneously maintain the biological activity of cells. In vitro studies reveal that 3D-printed hydrogels are beneficial for enhancing cell viability. Further, in vivo experiments demonstrate that cell-laden printed hydrogels significantly promote wound healing and re-epithelialization by modulating inflammation and accelerating collagen deposition and angiogenesis. Therefore, the proposed stepwise multi-cross-linking strategy is expected to accelerate the development of novel bioinks and promote the clinical applications of 3D bioprinting.

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