Modulating degradation of sodium alginate/bioglass hydrogel for improving tissue infiltration and promoting wound healing

Skin-inspired injectable adhesive gelatin/HA biocomposite hydrogel for hemostasis and full-thickness dermal wound healing

An insufficient adhesion to wet surfaces and biased functions for therapeutic efficacy are limitations to the application of gelatin and hyaluronic acid. Herein, we developed a simple double-injection approach to prepare a skin-inspired gelatin/HA-based injectable remoistenable adhesive hydrogel (HI/DA-Gel) through a simultaneous crosslinking and bio-compositing strategy of genipin incorporated with dopamine (DA) grafted gelatin and N-hydroxy succinimide (NHS) merged with hyaluronic acid. The integrative crosslinking and bio-compositing strategy led to the formation of a HI/DA-Gel with a highly skin-bionic interconnected internal double network 3D-structure with elevated surface wettability, thermal-stablity, adhesive and mechanical properties as expected. In vitro/in vivo biostudies showed that HI/DA-Gel enhanced collagen deposition, hemostatic effects and upregulated the production of CD31, showing an effective hemostasis and full-thickness dermal wound healing strategy. This work proposes a novel facile double-injection approach for the design of gelatin/ hyaluronic acid multi-functional injectable bio-composite hydrogels for integrated therapeutic effects.

Coaxially Fabricated Dual-Drug Loading Electrospinning Fibrous Mat with Programmed Releasing Behavior to Boost Vascularized Bone Regeneration

In clinical treatment, the bone regeneration of critical-size defects is desiderated to be solved, and the regeneration of large bone segment defects depends on early vascularization. Therefore, overcoming insufficient vascularization in artificial bone grafts may be a promising strategy for critical-size bone regeneration. Herein, a novel dual-drug programmed releasing electrospinning fibrous mat (EFM) with a deferoxamine (DFO)-loaded shell layer and a dexamethasone (DEX)-loaded core layer is fabricated using coaxial electrospinning technology, considering the temporal sequence of vascularization and bone repair. DFO acts as an angiogenesis promoter and DEX is used as an osteogenesis inducer. The results demonstrate that the early and rapid release of DFO promotes angiogenesis in human umbilical vascular endothelial cells and the sustained release of DEX enhances the osteogenic differentiation of rat bone mesenchymal stem cells. DFO and DEX exert synergetic effects on osteogenic differentiation via the Wnt/β-catenin signaling pathway, and the dual-drug programmed releasing EFM acquired perfect vascularized bone regeneration ability in a rat calvarial defect model. Overall, the study suggests a low-cost strategy to enhance vascularized bone regeneration by adjusting the behavior of angiogenesis and osteogenesis in time dimension.

Scalable Milk-Derived Whey Protein Hydrogel as an Implantable Biomaterial

There are limited naturally derived protein biomaterials for the available medical implants. High cost, low yield, and batch-to-batch inconsistency, as well as intrinsically differing bioactivity in some of the proteins, make them less beneficial as common implant materials compared to their synthetic counterparts. Here, we present a milk-derived whey protein isolate (WPI) as a new kind of natural protein-based biomaterial for medical implants. The WPI was methacrylated at 100 g bench scale, >95% conversion, and 90% yield to generate a photo-cross-linkable material. WPI-MA was further processed into injectable hydrogels, monodispersed microspheres, and patterned scaffolds with photo-cross-linking-based advanced processing methods including microfluidics and 3D printing. In vivo evaluation of the WPI-MA hydrogels showed promising biocompatibility and degradability. Intramyocardial implantation of injectable WPI-MA hydrogels in a model of myocardial infarction attenuated the pathological changes in the left ventricle. Our results indicate a possible therapeutic value of WPI-based biomaterials and give rise to a potential collaboration between the dairy industry and the production of medical therapeutics.

Preparation of Recombinant Human Collagen III Protein Hydrogels with Sustained Release of Extracellular Vesicles for Skin Wound Healing

Existing treatment methods encounter difficulties in effectively promoting skin wound healing, making this a serious challenge for clinical treatment. Extracellular vesicles (EVs) secreted by stem cells have been proven to contribute to the regeneration and repair of wound tissue, but they cannot be targeted and sustained, which seriously limits their current therapeutic potential. The recombinant human collagen III protein (rhCol III) has the advantages of good water solubility, an absence of hidden viral dangers, a low rejection rate and a stable production process. In order to achieve a site-specific sustained release of EVs, we prepared a rhCol III hydrogel by cross-linking with transglutaminase (TGase) from Streptomyces mobaraensis, which has a uniform pore size and good biocompatibility. The release profile of the rhCol III-EVs hydrogel confirmed that the rhCol III hydrogel could slowly release EVs into the external environment. Herein, the rhCol III-EVs hydrogel effectively promoted macrophage changing from type M1 to type M2, the migration ability of L929 cells and the angiogenesis of human umbilical vein endothelial cells (HUVECs). Furthermore, the rhCol III-EVs hydrogel is shown to promote wound healing by inhibiting the inflammatory response and promoting cell proliferation and angiogenesis in a diabetic rat skin injury model. The reported results indicate that the rhCol III-EVs hydrogel could be used as a new biological material for EV delivery, and has a significant application value in skin wound healing.

Assembly encapsulation of BSA and CCCH-ZAP in the sodium alginate/atractylodis macrocephalae system

Zinc finger antiviral proteins (ZAP) can significantly inhibit the replication of avian leukosis virus subgroup J (ALV-J), but the traditional method of ZAP administration is by injection, which can easily cause stress effects in chickens. In this work, we established a sodium alginate/atractylodis macrocephalae system for the encapsulation of CCCH-type zinc finger antiviral protein (CCCH-ZAP). Because of the high cost of ZAP, we first chose bovine serum albumin (BSA) as a model protein to investigate the encapsulation performance. The SEM images clearly confirmed that BSA and the sodium alginate/atractylodis macrocephalae system can assemble easily to form relatively stable nanostructures, and the encapsulation amount of BSA can reach 68%. Subsequently, the encapsulation of ZAP was studied. The SEM and the encapsulation experiments confirmed that ZAP can also be assembly encapsulated in the sodium alginate/atractylodis macrocephalae system with the encapsulation amount of 80%. Release studies showed that the SA/AM-ZAP nanocomposite was able to achieve a release rate of 32% of ZAP. This work successfully confirms the assembly encapsulation of ZAP, which will be beneficial for the usage of ZAP-based animal drugs.

ZAP and BSA can be encapsulated in the sodium alginate/atractylodis macrocephalae system using an assembly method.

Assembling Microgels via Dynamic Cross-Linking Reaction Improves Printability, Microporosity, Tissue-Adhesion, and Self-Healing of Microgel Bioink for Extrusion Bioprinting

Extrusion bioprinting has been widely used to fabricate complicated and heterogeneous constructs for tissue engineering and regenerative medicine. Despite the remarkable progress acquired so far, the exploration of qualified bioinks is still challenging, mainly due to the conflicting requirements on the printability/shape-fidelity and cell viability. Herein, a new strategy is proposed to formulate a dynamic cross-linked microgel assembly (DC-MA) bioink, which can achieve both high printability/shape-fidelity and high cell viability by strengthening intermicrogel interactions through dynamic covalent bonds while still maintaining the relatively low mechanical modulus of microgels. As a proof-of-concept, microgels are prepared by cross-linking hyaluronic acid modified with methacrylate and phenylboric acid groups (HAMA-PBA) and methacrylated gelatin (GelMA) via droplet-based microfluidics, followed by assembling into DC-MA bioink with a dynamic cross-linker (dopamine-modified hyaluronic acid, HA-DA). As a result, 2D and 3D constructs with high shape-fidelity can be printed without post-treatment, and the encapsulated L929 cells exhibit high cell viability after extrusion. Moreover, the addition of the dynamic cross-linker (HA-DA) also improves the microporosity, tissue-adhesion, and self-healing of the DC-MA bioink, which is very beneficial for tissue engineering and regenerative medicine applications including wound healing. We believe the present work sheds a new light on designing new bioinks for extrusion bioprinting.

Mussel-inspired adhesive bilayer hydrogels for bacteria-infected wound healing via NIR-enhanced nanozyme therapy

Preventing bacterial infection in situ and accelerating skin generation simultaneously are essentially important for wound healing. Herein, a mussel-inspired Ag nanozyme-based bilayer hydrogel is constructed to address the above concerns. The bilayer hydrogel is composed of a layer with large pores absorbing the wound exudate and allowing oxygen exchange and a layer with small pores keeping the wound moist and preventing bacterial invasion. Benefitting from the polydopamine (PDA) coating-reduced Ag nanoparticles (AgNPs), the hydrogel exhibits high near infrared (NIR) absorption at 808 nm to generate hyperthermia and NIR-enhanced peroxidase (POD-like) activity to produce hydroxyl radicals (•OH), which endows the hydrogel with excellent antibacterial properties when combined with the released Ag⁺. In addition, the hydrogel presents adhesiveness due to the catechol group on a PDA molecule. The in vivo test results demonstrate that the bilayer hydrogel can accelerate infected skin generation by facilitating collagen deposition, decreasing tumor necrosis factor-α secretion, and promoting vascular endothelial growth factor expression.