Drug-Loaded and Anisotropic Wood-Derived Hydrogel Periosteum with Super Antibacterial, Anti-Inflammatory, and Osteogenic Activities

Preparation and Characterization of Carboxymethyl Chitosan/Sodium Alginate Composite Hydrogel Scaffolds Carrying Chlorhexidine and Strontium-Doped Hydroxyapatite

Herein, we introduce a novel composite hydrogel scaffold designed for addressing infectious jaw defects, a significant challenge in clinical settings caused by the inherent limited self-regenerative capacity of bone tissues. The scaffold was engineered from a blend of carboxymethyl chitosan (CMCS)/sodium alginate (SA) hydrogel (CSH), β-cyclodextrin/chlorhexidine clathrate (β-CD-CHX), and strontium-nanohydroxyapatite nanoparticles (Sr-nHA). The β-CD-CHX and Sr-nHA components were synthesized using a saturated aqueous solution and a coprecipitation method, respectively. Subsequently, these elements were encapsulated within the CSH matrix. Comprehensive characterization of the CMCS/SA/β-CD-CHX/Sr-nHA composite hydrogel scaffold via scanning electron microscopy, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy validated the successful synthesis. The swelling and in vitro degradation behaviors proved that the composite hydrogel had good physical properties, while in vitro evaluations demonstrated favorable biocompatibility and osteoinductive properties. Additionally, antibacterial assessments revealed its effectiveness against common pathogens, Staphylococcus aureus and Escherichia coli. Overall, our results indicate that the CMCS/SA/β-CD-CHX/Sr-nHA composite hydrogel scaffolds exhibit significant potential for effectively treating infection-prone jaw defects.

Artificial periosteum promotes bone regeneration through synergistic immune regulation of aligned fibers and BMSC-recruiting phages

Given the crucial role of periosteum in bone repair, the use of artificial periosteum to induce spontaneous bone healing instead of using bone substitutes has become a potential strategy. Also, the proper transition from pro-inflammatory signals to anti-inflammatory signals is pivotal for achieving optimal repair outcomes. Hence, we designed an artificial periosteum loaded with a filamentous bacteriophage clone named P11, featuring an aligned fiber morphology. P11 endowed the artificial periosteum with the capacity to recruit bone marrow mesenchymal stem cells (BMSCs). The artificial periosteum also regulated the immune microenvironment at the bone injury site through the synergistic effects of biochemical factors and topography. Specifically, the inclusion of P11 preserved inflammatory signaling in macrophages and additionally facilitated the migration of BMSCs. Subsequently, aligned fibers stimulated macrophages, inducing alterations in cytoskeletal and metabolic activities, resulting in the polarization into the M2 phenotype. This progression encouraged the osteogenic differentiation of BMSCs and promoted vascularization. In vivo experiments showed that the new bone generated in the AP group exhibited the most efficient healing pattern. Overall, the integration of biochemical factors with topographical considerations for sequential immunomodulation during bone repair indicates a promising approach for artificial periosteum development. STATEMENT OF SIGNIFICANCE: The appropriate transition of macrophages from a pro-inflammatory to an anti-inflammatory phenotype is pivotal for achieving optimal bone repair outcomes. Hence, we designed an artificial periosteum featuring an aligned fiber morphology and loaded with specific phage clones. The artificial periosteum not only fostered the recruitment of BMSCs but also achieved sequential regulation of the immune microenvironment through the synergistic effects of biochemical factors and topography, and improved the effect of bone repair. This study indicates that the integration of biochemical factors with topographical considerations for sequential immunomodulation during bone repair is a promising approach for artificial periosteum development.

Anisotropic materials based on carbohydrate polymers: A review of fabrication strategies, properties, and applications

Anisotropic structures exist in almost all living organisms to endow them with superior properties and physiological functionalities. However, conventional artificial materials possess unordered isotropic structures, resulting in limited functions and applications. The development of anisotropic structures on carbohydrates is reported to have an impact on their properties and applications. In this review, various alignment strategies for carbohydrates (i.e., cellulose, chitin and alginate) from bottom-up to top-down strategies are discussed, including the rapidly developed innovative technologies such as shear-induced orientation through extrusion-based 3D/4D printing, magnetic-assisted alignment, and electric-induced alignment. The unique properties and wide applications of anisotropic carbohydrate materials across different fields, from biomedical, biosensors, smart actuators, soft conductive materials, to thermal management are also summarized. Finally, recommendations on the selection of fabrication strategies are given. The major challenge lies in the construction of long-range hierarchical alignment with high orientation degree and precise control over complicated architectures. With the future development of hierarchical alignment strategies, alignment control techniques, and alignment mechanism elucidation, the potential of anisotropic carbohydrate materials for scalable manufacture and clinical applications will be fully realized.

Dual Factor-Loaded Artificial Periosteum Accelerates Bone Regeneration

In the clinic, inactivation of osteosarcoma using microwave ablation would damage the periosteum, resulting in frequent postoperative complications. Therefore, the development of an artificial periosteum is crucial for postoperative healing. In this study, we prepared an artificial periosteum using silk fibroin (SF) loaded with stromal cell-derived factor-1α (SDF-1α) and calcitonin gene-related peptide (CGRP) to accelerate bone remodeling after the microwave ablation of osteosarcoma. The prepared artificial periosteum showed a sustained release of SDF-1α and CGRP after 14 days of immersion. In vitro culture of rat periosteal stem cells (rPDSCs) demonstrated that the artificial periosteum is favorable for cell recruitment, the activity of alkaline phosphatase, and bone-related gene expression. Furthermore, the artificial periosteum improved the tube formation and angiogenesis-related gene expression of human umbilical vein endothelial cells (HUVECs). In an animal study, the periosteum in the femur of a rabbit was inactivated through microwave ablation and then removed. The damaged periosteum was replaced with the as-prepared artificial periosteum and favored bone regeneration. In all, the designed dual-factor-loaded artificial periosteum is a promising strategy to replace the damaged periosteum in the therapy of osteosarcoma for a better bone-rebuilding process.

A Wood-Derived Periosteum for Spatiotemporal Drug Release: Boosting Bone Repair through Anisotropic Structure and Multiple Functions

Existing artificial periostea face many challenges, including difficult-to-replicate anisotropy in mechanics and structure, poor tissue adhesion, and neglected synergistic angiogenesis and osteogenesis. Here, inspired by natural wood (NW), a wood-derived elastic artificial periosteum is developed to mimic the structure and functions of natural periosteum, which combines an elastic wood (EW) skeleton, a polydopamine (PDA) binder layer, and layer-by-layer (LBL) biofunctional layers. Specifically, EW derived from NW is utilized as the anisotropic skeleton of artificial periosteum to guide cell directional behaviors, moreover, it also shows a similar elastic modulus and flexibility to natural periosteum. To further enhance its synergistic angiogenesis and osteogenesis, surface LBL biofunctional layers are designed to serve as spatiotemporal release platforms to achieve sequential and long-term release of pamidronate disodium (PDS) and deferoxamine (DFO), which are pre-encapsulated in chitosan (CS) and hyaluronic acid (HA) solutions, respectively. Furthermore, the combined effect of PDA coating and LBL biofunctional layers enables the periosteum to tightly adhere to damaged bone tissue. More importantly, this novel artificial periosteum can boost angiogenesis and bone formation in vitro and in vivo. This study opens up a new path for biomimetic design of artificial periosteum, and provides a feasible clinical strategy for bone repair.

Innovative Biomaterials for Bone Tumor Treatment and Regeneration: Tackling Postoperative Challenges and Charting the Path Forward

Surgical resection of bone tumors is the primary approach employed in the treatment of bone cancer. Simultaneously, perioperative interventions, particularly postoperative adjuvant anticancer strategies, play a crucial role in achieving satisfactory therapeutic outcomes. However, the occurrence of postoperative bone tumor recurrence, metastasis, extensive bone defects, and infection are significant risks that can result in unfavorable prognoses or even treatment failure. In recent years, there has been significant progress in the development of biomaterials, leading to the emergence of new treatment options for bone tumor therapy and bone regeneration. This progress report aims to comprehensively analyze the strategic development of unique therapeutic biomaterials with inherent healing properties and bioactive capabilities for bone tissue regeneration. These composite biomaterials, classified into metallic, inorganic non-metallic, and organic types, are thoroughly investigated for their responses to external stimuli such as light or magnetic fields, internal interventions including chemotherapy or catalytic therapy, and combination therapy, as well as their role in bone regeneration. Additionally, an overview of self-healing materials for osteogenesis is provided and their potential applications in combating osteosarcoma and promoting bone formation are explored. Furthermore, the safety concerns of integrated materials and current limitations are addressed, while also discussing the challenges and future prospects.

Biomimetic cryogel promotes the repair of osteoporotic bone defects through altering the ROS niche via down-regulating the ROMO1

Osteoporosis is a systemic bone disease that is prone to fractures due to decreased bone density and bone quality, and delayed union or nonunion often occurs in osteoporotic fractures. Therefore, it is particularly important to develop tissue engineering materials to promote osteoporotic fracture healing. In this study, a series of biomimetic cryogels prepared from the decellularized extracellular matrix (dECM), methacrylate gelatin (GelMA), and carboxymethyl chitosan (CMCS) via unidirectional freezing, photo- and genipin crosslinking were applied for the regeneration of osteoporotic fractures. Specifically, dECM extracted from normal or osteoporotic rats was applied for the preparation of the cryogels, named as GC-Normal dECM or GC-OVX dECM, respectively. It was verified that the GC-Normal dECM demonstrated superior performance in promoting the proliferation of BMSCs isolated from osteoporotic rats (OVX-BMSCs), and the differentiation of OVX-BMSCs into osteoblasts both in vitro and in vivo. RNA sequencing and further verifications confirmed that GC-Normal dECM cryogel could scavenge the intracellular reactive oxygen species (ROS) in OVX-BMSCs to accelerate the regeneration of osteoporotic fracture by down-regulating the reactive oxygen species modulator 1 (Romo1). The results indicated that by regulating the ROS niche of OVX-BMSCs, biomimetic the GC-Normal dECM cryogel was expected to be a clinical candidate for repairing osteoporotic bone defects.

Highly anisotropic and elastic cellulosic scaffold guiding cell orientation and osteogenic differentiation via topological and mechanical cues

Inspired by the similarity of anisotropic channels in wood to the canals of bone, the elastic wood-derived (EW) scaffolds with anisotropic channels were prepared via simple delignification treatment of natural wood (NW). We hypothesize that the degree of delignification will lead to differences in mechanical properties of scaffolds, which in turn directly affect the behaviors and fate of stem cells. The delignification process did not destroy the anisotropic channel structure of the scaffolds, but endowed the scaffolds with good elasticity and rapid stress relaxation. Interestingly, the micron-scale anisotropic channels of the scaffolds can highly promote the polarization of cells along the direction of channels. We also found that the alkaline phosphatase of EW scaffold can reach to about 13.1 U/gprot, which was about double that of NW scaffold. Moreover, the longer the delignification time, the better the osteogenic activity of the EW scaffolds. We further hypothesize that the osteogenic activity of scaffolds is related to the stress relaxation properties. The immunofluorescence staining showed that when the stress relaxation time of scaffold was shortened to about 10 s, the nuclear ratio of YAP of scaffold increased to 0.22, which well supports our hypothesis.

Direct osteogenesis and immunomodulation dual function via sustained release of naringin from the polymer scaffold

Many traditional Chinese medicine monomers, such as naringin (NG), can regulate the local immune microenvironment to benefit osteogenesis. However, the rapid release of NG from scaffolds severely influences the osteogenesis-promoting effect. Herein, NG was loaded into mesoporous bioglass (MBG) to achieve sustained release through physical adsorption and the barrier role of mesoporous channels, then MBG loaded with NG was added to poly(L-lactic acid) (PLLA) to fabricate composite scaffolds by selective laser sintering (SLS) technology. The results showed that the NG-MBG/PLLA scaffolds could continuously and slowly release NG for 14 days compared with NG/PLLA scaffolds, and the cumulative release amount for the NG-MBG/PLLA scaffolds was 44.26%. In addition, the NG-MBG/PLLA scaffolds can promote the proliferation and osteogenesis differentiation of mouse bone marrow mesenchymal stem cells (mBMSCs). Meanwhile, the composite scaffolds decreased the reactive oxygen species (ROS) level of RAW264.7 under the stimulation of lipopolysaccharide (LPS) and significantly suppressed interleukin-6 (IL-6) and enhanced arginase-1 (Arg-1) protein expressions. Moreover, calcium nodule and alkaline phosphatase production of mBMSCs in a macrophage-conditioned medium for the NG-MBG/PLLA group also evidently increased compared with the PLLA and MBG/PLLA groups. These NG sustained-release composite scaffolds with osteo-immunomodulation function have great application prospects in the clinic.

Current advances in anisotropic structures for enhanced osteogenesis

Bone defects are a challenge to healthcare systems, as the aging population experiences an increase in bone defects. Despite the development of biomaterials for bone fillers and scaffolds, there is still an unmet need for a bone-mimetic material. Cortical bone is highly anisotropic and displays a biological liquid crystalline (LC) arrangement, giving it exceptional mechanical properties and a distinctive microenvironment. However, the biofunctions, cell-tissue interactions, and molecular mechanisms of cortical bone anisotropic structure are not well understood. Incorporating anisotropic structures in bone-facilitated scaffolds has been recognised as essential for better outcomes. Various approaches have been used to create anisotropic micro/nanostructures, but biomimetic bone anisotropic structures are still in the early stages of development. Most scaffolds lack features at the nanoscale, and there is no comprehensive evaluation of molecular mechanisms or characterisation of calcium secretion. This manuscript provides a review of the latest development of anisotropic designs for osteogenesis and discusses current findings on cell-anisotropic structure interactions. It also emphasises the need for further research. Filling knowledge gaps will enable the fabrication of scaffolds for improved and more controllable bone regeneration.

Highly sensitive, wide-pressure and low-frequency characterized pressure sensor based on piezoresistive-piezoelectric coupling effects in porous wood

Lightweight and highly compressible materials have received considerable attention in flexible pressure sensing devices. In this study, a series of porous woods (PWs) are produced by chemical removal of lignin and hemicellulose from natural wood by tuning treatment time from 0 to 15 h and extra oxidation through H₂O₂. The prepared PWs with apparent densities varying from 95.9 to 46.16 mg/cm³ tend to form a wave-shaped interwoven structure with improved compressibility (up to 91.89 % strain under 100 kPa). The sensor assembled from PW with treatment time of 12 h (PW-12) exhibits the optimal piezoresistive-piezoelectric coupling sensing properties. For the piezoresistive properties, it has high stress sensitivity of 15.14 kPa^-1, covering a wide linear working pressure range of 0.06-100 kPa. For its piezoelectric potential, PW-12 shows a sensitivity of 0.443 V·kPa^-1 with ultralow frequency detection as low as 0.0028 Hz, and good cyclability over 60,000 cycles under 0.41 Hz. The nature-derived all-wood pressure sensor shows obvious superiority in the flexibility for power supply requirement. More importantly, it presents fully decoupled signals without cross-talks in the dual-sensing functionality. Sensor like this is capable of monitoring various dynamic human motions, making it an extremely promising candidate for the next generation artificial intelligence products.

Highly Elastic and Anisotropic Wood-Derived Composite Scaffold with Antibacterial and Angiogenic Activities for Bone Repair

Scaffold-based tissue engineering is a promising strategy to address the rapidly growing demand for bone implants, but developing scaffolds with bone extracellular matrix-like structures, suitable mechanical properties, and multiple biological activities remains a huge challenge. Here, it is aimed to develop a wood-derived composite scaffold with an anisotropic porous structure, high elasticity, and good antibacterial, osteogenic, and angiogenic activities. First, natural wood is treated with an alkaline solution to obtain a wood-derived scaffold with an oriented cellulose skeleton and high elasticity, which can not only simulate collagen fiber skeleton in bone tissue but also greatly improve the convenience of clinical implantation. Subsequently, chitosan quaternary ammonium salt (CQS) and dimethyloxalylglycine (DMOG) are further modified on the wood-derived elastic scaffold through a polydopamine layer. Among them, CQS endows the scaffold with good antibacterial activity, while DMOG significantly improves the scaffold's osteogenic and angiogenic activities. Interestingly, the mechanical characteristics of the scaffolds and the modified DMOG can synergistically enhance the expression of yes-associated protein/transcriptional co-activator with PDZ binding motif signaling pathway, thereby effectively promoting osteogenic differentiation. Therefore, this wood-derived composite scaffold is expected to have potential application in the treatment of bone defects.

Recent advances in adhesive materials used in the biomedical field: adhesive properties, mechanism, and applications

Adhesive materials are natural or synthetic polymers with the ability to adhere to the surface of luminal mucus or epithelial cells. They are widely used in the biomedical field due to their unique adhesion, biocompatibility, and excellent surface properties. When used in the human body, they can adhere to an accessible target and remain at the focal site for a longer period, improving the therapeutic effect on local disease. An adhesive material with bacteriostatic properties can play an antibacterial role at the focal site and the adhesive properties of the material can prevent the focal site from being infected by bacteria for a period. In addition, some adhesive materials can promote cell growth and tissue repair. In this review, the properties and mechanism of natural adhesive materials, organic adhesive materials, composite adhesive materials, and underwater adhesive materials have been introduced systematically. The applications of these adhesive materials in drug delivery, antibacterials, tissue repair, and other applications are described in detail. Finally, we have discussed the prospects and challenges of using adhesive materials in the field of biomedicine.

Mesenchymal Stem Cells and Their Exocytotic Vesicles

Mesenchymal stem cells (MSCs), as a kind of pluripotent stem cells, have attracted much attention in orthopedic diseases, geriatric diseases, metabolic diseases, and sports functions due to their osteogenic potential, chondrogenic differentiation ability, and adipocyte differentiation. Anti-inflammation, anti-fibrosis, angiogenesis promotion, neurogenesis, immune regulation, and secreted growth factors, proteases, hormones, cytokines, and chemokines of MSCs have been widely studied in liver and kidney diseases, cardiovascular and cerebrovascular diseases. In recent years, many studies have shown that the extracellular vesicles of MSCs have similar functions to MSCs transplantation in all the above aspects. Here we review the research progress of MSCs and their exocrine vesicles in recent years.