A "Nonsolvent Quenching" Strategy for 3D Printing of Polysaccharide Scaffolds with Immunoregulatory Accuracy

A Highly Adaptable Hydrogen Bond Re-Orientation (HyBRO) Strategy for Multiscale Vasculature Fabrication

Three-dimensional printing of microchannel networks mimicking native vasculature provides essential functions for biomedical applications. However, developing a highly "adaptable" technique - that can adjust to diverse materials choices, high shape accuracy, and broad size ranges - for producing physiologically responsive vasculature remains challenging. Here, an innovative hydrogen bond re-orientation (HyBRO) strategy for microchannel network fabrication is reported. By identifying interfacial instability of sacrificial material (SM) during embedding as a core limitation, this strategy prints the SM into an optimal "nonsolvent" to shape the desirable channel structure. In this process, the nonsolvent instantaneously switches the SM from forming hydrogen bonds with exterior water to forming interior linkages inside it. This transition protects the SM from external solvent "erosion" upon re-exposure to embedding material, inhibiting deformation. Consequently, this approach enables the creation of accurate (>90%), multiscale (10-fold), hierarchical microchannel networks, accommodating accurate printing of a wide range of ink materials - extending from typical hydrophilic polymers into non-typical hydrophobic ones. Further biological tests demonstrate that HyBRO-produced vasculature recapitulates not only essential endothelial barrier function but also delicate ion-channel responses to varying shear stresses, highlighting its potential for engineering physiologically responsive vasculature in broad applications.

Morphology Effect of Puffball Spores on Hemostasis: A Promising Solution for Hemostatic Challenges

Hemostatic materials play a crucial role in wound healing by promoting blood concentration or releasing procoagulant factors. While hydrophilic hemostatic materials are effective, they may cause excessive blood loss and difficulty removing from the wound. Conversely, hydrophobic hemostatic materials avoid these issues but may hinder blood concentration and the release of procoagulant factors due to their water-repellent nature. This study investigates the hemostatic properties and underlying mechanism of puffball (Bovistella sp.) spores, a traditional hemostatic material. The unique hollow ball-rod morphology and strong water affinity of puffball spores enable efficient water removal, leading to improved blood clotting without the drawbacks typically associated with hydrophilic hemostatic materials. Further analysis reveals that the nano-protrusions on the spore surface create a textured hydrophobic surface due to the pinning effect, which prevents adhesion to the wound after clotting. Overall, puffball spores exhibit hemostatic efficacy comparable to the commercial agent QuikClot, with enhanced safety and reduced side effects. Their characteristic morphology, physicochemical properties, and chemical compositions offer inspiration for advancing hemostatic materials and addressing current challenges in wound healing. Additionally, this work provides new perspectives for insight into the pharmacological substance basis of traditional medicine, expanding beyond the conventional component-focused mentality to a material-based insight.

H-Bonds Enhanced Natural Polyphenols Bined Polysaccharide/Gelatin Composites with Controlled Photothermal Stimulation Phase Transition for Wound Care

Severe open wounds should be closed immediately and regularly undergo re-examination and debridement. Therefore, dressings should effectively cover the wound, creating a moist environment for healing while meeting mechanical requirements for daily movement and adaptability. Herein, a low-cost and easy-to-prepare plant polysaccharide hydrogel was reported. The Mesona chinensis Benth polysaccharide strengthened the hydrogel network by hydrogen bonding and changed the phase transition temperature, but retained the thermal response characteristics of the hydrogel. By adjusting the polysaccharide concentration, MepGel(1) can be prepared to remain stable as a semisolid at body temperature and transform into a shear-thinning semifluid state when appropriately heated. The composite hydrogel could be easily shaped, effectively closing wounds of different shapes, while maintaining excellent mechanical properties. Importantly, this composite hydrogel had a near-infrared photothermal effect resulting in excellent antibacterial effect and collided with its own thermal response producing functions conducive to wound care, like accelerating the self-healing of the dressing, achieving re-adhesion, and further covering the wound. Furthermore, the hydrogel had excellent biocompatibility, enhancing immunity and promoting healing of bacterial-infected wounds. The low cost and rich functionality demonstrated by MepGel had the potential to face the enormous challenges and economic burden of clinical wound healing.

Spermidine-Functionalized Injectable Hydrogel Reduces Inflammation and Enhances Healing of Acute and Diabetic Wounds In Situ

The inflammatory response is a key factor affecting tissue regeneration. Inspired by the immunomodulatory role of spermidine, an injectable double network hydrogel functionalized with spermidine (DN-SPD) is developed, where the first and second networks are formed by dynamic imine bonds and non-dynamic photo-crosslinked bonds respectively. The single network hydrogel before photo-crosslinking exhibits excellent injectability and thus can be printed and photo-crosslinked in situ to form double network hydrogels. DN-SPD hydrogel has demonstrated desirable mechanical properties and tissue adhesion. More importantly, an "operando" comparison of hydrogels loaded with spermidine or diethylenetriamine (DETA), a sham molecule resembling spermidine, has shown similar physical properties, but quite different biological functions. Specifically, the outcomes of 3 sets of in vivo animal experiments demonstrate that DN-SPD hydrogel can not only reduce inflammation caused by implanted exogenous biomaterials and reactive oxygen species but also promote the polarization of macrophages toward regenerative M2 phenotype, in comparison with DN-DETA hydrogel. Moreover, the immunoregulation by spermidine can also translate into faster and more natural healing of both acute wounds and diabetic wounds. Hence, the local administration of spermidine affords a simple but elegant approach to attenuate foreign body reactions induced by exogenous biomaterials to treat chronic refractory wounds.

Covalent Bond Interfacial Recognition of Polysaccharides/Silica Reinforced High Internal Phase Pickering Emulsions for 3D Printing

Significant challenges remain in designing sufficient viscoelasticity polysaccharide-based high internal phase Pickering emulsions (HIPPEs) as soft materials for 3D printing. Herein, taking advantage of the interfacial covalent bond interaction between modified alginate (Ugi-OA) dissolved in the aqueous phase and aminated silica nanoparticles (ASNs) dispersed in oil, HIPPEs with printability were obtained. Using multitechniques coupling a conventional rheometer with a quartz crystal microbalance with dissipation monitoring, the correlation between interfacial recognition coassembly on the molecular scale and the stability of whole bulk HIPPEs on the macroscopic scale can be clarified. The results showed that Ugi-OA/ASNs assemblies (NPSs) were strongly retargeted into the oil-water interface due to the specific Schiff base-binding between ASNs and Ugi-OA, further forming thicker and more rigid interfacial films on the microscopic scale compared with that of the Ugi-OA/SNs (bared silica nanoparticles) system. Meanwhile, flexible polysaccharides also formed a 3D network that suppressed the motion of the droplets and particles in the continuous phase, endowing the emulsion with appropriately viscoelasticity to manufacture a sophisticated "snowflake" architecture. In addition, this study opens a novel pathway for the construction of structured all-liquid systems by introducing an interfacial covalent recognition-mediated coassembly strategy, showing promising applications.

Differential Foreign Body Reactions between Branched and Linear Glucomannan Scaffolds

The extent and patterns of foreign body reaction (FBR) influence the function and feasibility of biomaterials. Polysaccharides, as an important biomaterial category, have received increasing attention in diverse biomaterials design and biomedical applications due to their excellent polymeric and biocompatible characteristics. Their biological effects are usually associated with their monosaccharide composition or functional groups, yet the contribution of their glycan structure is still unknown. Herein, two glucomannans, similar in composition and molecular weight with differences in glycan structure, linear-chain (Konjac glucomannan, KGM), and branched-chain (Bletilla striata polysaccharide, BSP), were adopted to explore the host-biomaterials interaction. After acetyl modification, these polysaccharides were fabricated into electrospun scaffolds to reduce the impacts derived from the physical properties and surface morphology. According to a systematic study of their biological effects on immune cells and host response in a subcutaneous implantation model in vivo, it was revealed that acetyl KGM (acKGM) scaffolds caused a stronger FBR than acetyl BSP materials. Additionally, acKGM could stimulate macrophages to release pro-inflammatory cytokines, suggesting the influence of sugar chain arrangement on FBR and providing clues for the fine regulation of immune response and novel biomaterials design.