A facile Immunoregulatory Constructional Design by Proanthocyanidin Optimizing Directional Chitosan Microchannel.

Improving the interconnected structure and bioregulatory function of natural chitosan is beneficial for optimizing its performance in bone regeneration. Here, a facile immunoregulatory constructional design is proposed for developing instructive chitosan by directional freezing and alkaline salting out. The molecular dynamics simulation confirmed the assembly kinetics and structural features of various polyphenols and chitosan molecules. Along with the in vitro anti-inflammatory, antioxidative, promoting bone mesenchymal stem cell (BMSC) adhesion and proliferation performance, proanthocyanidin optimizing chitosan (ChiO) scaffold presented an optimal immunoregulatory structure with the directional microchannel. Transcriptome analysis in vitro further revealed the cytoskeleton- and immune-regulation effect of ChiO are the key mechanism of action on BMSC. The rabbit cranial defect model (Φ = 10 mm) after 12 weeks of implantation confirmed the significantly enhanced bone reconstitution. This facile immunoregulatory directional microchannel design provides effective guidance for developing inducible chitosan scaffolds.

DLP Fabrication of Multiple Hierarchical Biomimetic GelMA/SilMA/HAp Scaffolds for Enhancing Bone Regeneration.

Severe bone defects resulting from trauma and diseases remain a persistent clinical challenge. In this study, a hierarchical biomimetic microporous hydrogel composite scaffold was constructed by mimicking the hierarchical structure of bone. Initially, gelatin methacrylamide (GelMA) and methacrylic anhydride silk fibroin (SilMA) were synthesized, and GelMA/SilMA inks with suitable rheological and mechanical properties were prepared. Biomimetic micropores were then generated by using an aqueous two-phase emulsification method. Subsequently, biomimetic microporous GelMA/SilMA was mixed with hydroxyapatite (HAp) to prepare biomimetic microporous GelMA/SilMA/HAp ink. Hierarchical biomimetic microporous GelMA/SilMA/HAp (M-GSH) scaffolds were then fabricated through digital light processing (DLP) 3D printing. Finally, in vitro experiments were conducted to investigate cell adhesion, proliferation, and inward migration as well as osteogenic differentiation and vascular regeneration effects. In vivo experiments indicated that the biomimetic microporous scaffold significantly promoted tissue integration and bone regeneration after 12 weeks of implantation, achieving 42.39% bone volume fraction regeneration. In summary, this hierarchical biomimetic microporous scaffold provides a promising strategy for the repair and treatment of bone defects.

Nucleation Domains in Biomineralization: Biomolecular Sequence and Conformational Features.

Biomolecules play a vital role in the regulation of biomineralization. However, the characteristics of practical nucleation domains are still sketchy. Herein, the effects of the representative biomolecular sequence and conformations on calcium phosphate (Ca-P) nucleation and mineralization are investigated. The results of computer simulations and experiments prove that the line in the arrangement of dual acidic/essential amino acids with a single interval (Bc (Basic) -N (Neutral) -Bc-N-Ac (Acidic)- NN-Ac-N) is most conducive to the nucleation. 2α-helix conformation can best induce Ca-P ion cluster formation and nucleation. "Ac- × × × -Bc" sequences with α-helix are found to be the features of efficient nucleation domains, in which process, molecular recognition plays a non-negligible role. It further indicates that the sequence determines the potential of nucleation/mineralization of biomolecules, and conformation determines the ability of that during functional execution. The findings will guide the synthesis of biomimetic mineralized materials with improved performance for bone repair.

Hydrophobic Tetracycline Immobilized in Fibrous Hyaluronan Regulates Adhesive Collagen-Based Hydrogel Stability for Infected Wound Healing.

Collagen-based hydrogels have a significant impact on wound healing, but they suffer from structural instability and bacterial invasion in infected wounds. Here, electrospun nanofibers of esterified hyaluronan (HA-Bn/T) are developed to immobilize the hydrophobic antibacterial drug tetracycline by π-π stacking interaction. Dopamine-modified hyaluronan and HA-Bn/T are employed simultaneously to stabilize the structure of collagen-based hydrogel by chemically interweaving the collagen fibril network and decreasing the rate of collagen degradation. This renders it injectable for in situ gelation, with suitable skin adhesion properties and long-lasting drug release capability. This hybridized interwoven hydrogel promotes the proliferation and migration of L929 cells and vascularization in vitro. It presents satisfactory antibacterial ability against Staphylococcus aureus and Escherichia coli. The structure also retains the functional protein environment provided by collagen fiber, inhibits the bacterial environment of infected wounds, and modulates local inflammation, resulting in neovascularization, collagen deposition, and partial follicular regeneration. This strategy offers a new solution for infected wound healing.

Construction of Microfluidic Chip Structure for Cell Migration Studies in Bioactive Ceramics.

Cell migration is an essential bioactive ceramics property and critical for bone induction, clinical application, and mechanism research. Standardized cell migration detection methods have many limitations, including a lack of dynamic fluid circulation and the inability to simulate cell behavior in vivo. Microfluidic chip technology, which mimics the human microenvironment and provides controlled dynamic fluid cycling, has the potential to solve these questions and generate reliable models of cell migration in vitro. In this study, a microfluidic chip is reconstructed to integrate the bioactive ceramic into the microfluidic chip structure to constitute a ceramic microbridge microfluidic chip system. Migration differences in the chip system are measured. By combining conventional detection methods with new biotechnology to analyze the causes of cell migration differences, it is found that the concentration gradients of ions and proteins adsorbed on the microbridge materials are directly related to the occurrence of cell migration behavior, which is consistent with previous reports and demonstrates the effectiveness of the microfluidic chip model. This model provides in vivo environment simulation and controllability of input and output conditions superior to standardized cell migration detection methods. The microfluidic chip system provides a new approach to studying and evaluating bioactive ceramics.

Covalently Grafted Biomimetic Matrix Reconstructs the Regenerative Microenvironment of the Porous Gradient Polycaprolactone Scaffold to Accelerate Bone Remodeling.

Integrating a biomimetic extracellular matrix to improve the microenvironment of 3D printing scaffolds is an emerging strategy for bone substitute design. Here, a "soft-hard" bone implant (BM-g-DPCL) consisting of a bioactive matrix chemically integrated on a polydopamine (PDA)-coated porous gradient scaffold by polyphenol groups is constructed. The PDA-coated "hard" scaffolds promoted Ca2+ chelation and mineral deposition; the "soft" bioactive matrix is beneficial to the migration, proliferation, and osteogenic differentiation of stem cells in vitro, accelerated endogenous stem cell recruitment, and initiated rapid angiogenesis in vivo. The results of the rabbit cranial defect model (Φ = 10 mm) confirmed that BM-g-DPCL promoted the integration between bone tissue and implant and induced the deposition of bone matrix. Proteomics confirmed that cytokine adhesion, biomineralization, rapid vascularization, and extracellular matrix formation are major factors that accelerate bone defect healing. This strategy of highly chemically bonded soft-hard components guided the construction of the bioactive regenerative scaffold.

Electrospun Hyaluronan Nanofiber Membrane Immobilizing Aromatic Doxorubicin as Therapeutic and Regenerative Biomaterial.

Lesioned tissue requires synchronous control of disease and regeneration progression after surgery. It is necessary to develop therapeutic and regenerative scaffolds. Here, hyaluronic acid (HA) was esterified with benzyl groups to prepare hyaluronic acid derivative (HA-Bn) nanofibers via electrospinning. Electrospun membranes with average fiber diameters of 407.64 ± 124.8 nm (H400), 642.3 ± 228.76 nm (H600), and 841.09 ± 236.86 nm (H800) were obtained by adjusting the spinning parameters. These fibrous membranes had good biocompatibility, among which the H400 group could promote the proliferation and spread of L929 cells. Using the postoperative treatment of malignant skin melanoma as an example, the anticancer drug doxorubicin (DOX) was encapsulated in nanofibers via hybrid electrospinning. The UV spectroscopy of DOX-loaded nanofibers (HA-DOX) revealed that DOX was successfully encapsulated, and there was a π-π interaction between aromatic DOX and HA-Bn. The drug release profile confirmed the sustained release of about 90%, achieved within 7 days. In vitro cell experiments proved that the HA-DOX nanofiber had a considerable inhibitory effect on B16F10 cells. Therefore, the HA-Bn electrospun membrane could facilitate the potential regeneration of injured skin tissues and be incorporated with drugs to achieve therapeutic effects, offering a powerful approach to developing therapeutic and regenerative biomaterial.

Preparation and Properties of Double-Crosslinked Hydroxyapatite Composite Hydrogels.

Natural polymer hydrogels have good mechanical properties and biocompatibility. This study designed hydroxyapatite-enhanced photo-oxidized double-crosslinked hydrogels. Hyaluronic acid (HA) and gelatin (Gel) were modified with methacrylate anhydride. The catechin group was further introduced into the HA chain inspired by the adhesion chemistry of marine mussels. Hence, the double-crosslinked hydrogel (HG) was formed by the photo-crosslinking of double bonds and the oxidative-crosslinking of catechins. Moreover, hydroxyapatite was introduced into HG to form hydroxyapatite-enhanced hydrogels (HGH). The results indicate that, with an increase in crosslinking network density, the stiffness of hydrogels became higher; these hydrogels have more of a compact pore structure, their anti-degradation property is improved, and swelling property is reduced. The introduction of hydroxyapatite greatly improved the mechanical properties of hydrogels, but there is no change in the stability and crosslinking network structure of hydrogels. These inorganic phase-enhanced hydrogels were expected to be applied to tissue engineering scaffolds.

[Research Progress in Promotion of Tissue Regeneration and Reconstruction with Exosomes Derived from Mesenchymal Stem Cells].

In regenerative medicine, stem cell therapy is an effective strategy for tissue regeneration and has a positive therapeutic effect on the regeneration and repair of defective tissues. In recent years, a series of studies have shown that the positive effects of stem cell therapy are mediated by exosomes released by the paracrine action of mesenchymal stem cells. Researchers have thus proposed a novel treatment strategy to use stem-cell-derived exosomes alone for tissue regeneration and repair, and affirmed through studies that the effects achieved were comparable to those of stem-cell-based therapies. Therefore, as a promising treatment strategy, exosome-based tissue regeneration treatment measures have been extensively studied. In this review, we discussed the latest knowledge of exosomes and the research progress in the regeneration and repair of related connective tissues, including the regeneration of bones, cartilage, skin, spinal cord and tendons, and briefly discussed the corresponding mechanisms. In addition, the challenges and prospects of tissue regeneration and repair based on mesenchymal stem cell exosomes were discussed.

[Role of Stem Cells and Their Biomimetic Matrix Microenvironment in Regenerative Repair of Articular Cartilage: A Review].

It is difficult for the articular cartilage to self-heal any damage it may incur due to its lack of nerves and blood vessels. Development in stem cell technology provides new prospects for articular cartilage regeneration. Currently, stem cells from different sources and their diverse applications have demonstrated different degrees of therapeutic effect and potential in articular cartilage repair. However, stem cells are highly sensitive to their microenvironment. Therefore, more and more researchers are focusing their attention on regulating stem cells and thus accelerating cartilage regeneration through the biomimetic microenvironment constructed by biologically functional scaffolds. We reviewed in this paper the sources of the stem cells used for cartilage repair, the application method of these stem cells, as well as the therapeutic effect, mechanism and limitations in the application of stem cells synergizing with the biomimetic microenvironment in promoting articular cartilage repair and regeneration. We hoped to provide suggestions for practical clinical research in the design and improvement of biofunctional cartilage repair scaffolds that synergize with stem cells.

Genetic portrait and phylogenetic analysis of an Aksu Uyghur population based on the 19 X-STR system.

The X chromosome has a special mode of inheritance, and is thus a rich resource for population studies. In this study, the allele frequencies and forensic statistics of the 19 X chromosomal short tandem repeat loci were evaluated in 500 Uyghur individuals from Aksu Prefecture in northwest China. We further aimed to study whether the Uyghur populations located in various regions of Xinjiang share similar allele and haplotype frequency distributions, as they have experienced genetic exchanges. Population comparisons, PCA and MDS were performed for the Uyghurs and 27 populations and the results indicate that the Uyghur minority in Aksu has a relatively close phylogenetic relationship with East Asians, especially the Kazakh minority.

In vivo immunological properties research on mesenchymal stem cells based engineering cartilage by a dialyzer pocket model.

As the seed cells, the immune properties of the mesenchymal stem cells are important for the tissue engineering restoring effect. But the in vivo research model is lacking. In the study, based on a dialyzer pocket model, changes in immunological properties and the differentiation of seeded mesenchymal stem cells (MSCs) in collagen hydrogel were studied in muscle and articular cavity implantation, respectively. The results showed that collagen hydrogel can induce MSCs to form cartilage tissue, followed by alteration of immunological properties. In muscle implantation, relatively low expression of major histocompatibility complex (MHC) molecules and low level of one-way mixed lymphocyte reactions (MLR) on the seeded MSCs were observed, but only a little cartilage tissue formed. In articular cavity implantation, more cartilage tissue formed, but higher MHC expressions and MLR level were found. Results indicated that the immunomodulation and the cartilage formation of the seeded MSCs will be impacted by the scaffold and the environment of the in vivo implanted site. The dialyzer pocket model can be used for the in vivo research for the MSC-based strategy of the tissue engineering, especially for the optimization of the immunomodulation.

Bio-Functional Design, Application and Trends in Metallic Biomaterials.

Introduction of metals as biomaterials has been known for a long time. In the early development, sufficient strength and suitable mechanical properties were the main considerations for metal implants. With the development of new generations of biomaterials, the concepts of bioactive and biodegradable materials were proposed. Biological function design is very import for metal implants in biomedical applications. Three crucial design criteria are summarized for developing metal implants: (1) mechanical properties that mimic the host tissues; (2) sufficient bioactivities to form bio-bonding between implants and surrounding tissues; and (3) a degradation rate that matches tissue regeneration and biodegradability. This article reviews the development of metal implants and their applications in biomedical engineering. Development trends and future perspectives of metallic biomaterials are also discussed.

Influences of the steam sterilization on the properties of calcium phosphate porous bioceramics.

The influences of steam sterilization on the physicochemical properties of calcium phosphate (Ca-P) porous bioceramics, including ß-tricalcium phosphate (ß-TCP), biphasic calcium phosphate (BCP) and hydroxyapatite (HA) are investigated. After being steam sterilized in an autoclave (121 °C for 40 min), the porous bioceramics are dried and characterized. The steam sterilization has no obvious effects on the phase composition, thermal stability, pH value and dissolubility of ß-TCP porous bioceramic, but changes its morphology and mechanical strength. Meanwhile, the steam sterilization leads to the significant changes of the morphology, phase composition, pH value and dissolubility of BCP porous bioceramic. The increase of dissolubility and mechanical strength, the decrease of pH value of the immersed solution and partial oriented growth of crystals are also observed in HA porous bioceramic after steam sterilization. These results indicate that the steam sterilization can result in different influences on the physicochemical properties of ß-TCP, BCP and HA porous bioceramics, thus the application of the steam sterilization on the three kinds of Ca-P porous bioceramics should be considered carefully based on the above changed properties.

Engineering Injectable Coassembled Hydrogel by Photothermal Driven Chitosan-Stabilized MoS2 Nanosheets for Infected Wound Healing.

The application of enzyme-like molybdenum disulfide (MoS2) in tissue repair was confronted with stable dispersion, solubilization, and biotoxicity. Here, the injectable self-healing hydrogel was successfully designed using a step-by-step coassembly of chitosan and MoS2. Polyphenolic chitosan as a "structural stabilizer" of MoS2 nanosheets reconstructed well-dispersed MoS2@CSH nanosheets, which improved the biocompatibility of traditional MoS2, and strengthened its photothermal conversion and enzyme-like activities, guaranteeing highly efficient radical scavenging and antimicrobial properties. Furthermore, the polyphenol chitosan was employed again as a "molecular cross-linking agent" to form the injectable NIR-responsive MoS2@CSH hydrogel by accelerating hydrogen-bond interaction among chitosan and the multicross-linking reaction among polyphenols. The rapid self-healing ability was conducive to wound closure and dynamic adaptability. An experimental study on infected wound healing demonstrated that MoS2@CSH hydrogel could substantially eradicate bacteria and accelerate the angiogenesis of infected wounds. The photothermal-driven coassembly of MoS2 and polycation provided an alternative strategy for infected wound healing.

Hollow Copper Sulfide Photothermal Nanodelivery Platform Boosts Angiogenesis of Diabetic Wound by Scavenging Reactive Oxygen Species.

Sharply rising oxidative stress and ineffectual angiogenesis have imposed restrictions on diabetic wound healing. Here, a photothermal-responsive nanodelivery platform (HHC) was prepared by peroxidase (CAT)-loaded hollow copper sulfide dispersed in photocurable methacrylamide hyaluronan. The HHC could scavenge reactive oxygen species (ROS) and promote angiogenesis by photothermally driven CAT and Cu2+ release. Under near-infrared light irradiation, the HHC presented safe photothermal performance (<43 °C), efficient bacteriostatic ability against E. coli and S. aureus. It could rapidly release CAT into the external environment for decomposing H2O2 and oxygen generation to alleviate oxidative stress while promoting fibroblast migration and VEGF protein expression of endothelial cells by reducing intracellular ROS levels. The nanodelivery platform presented satisfactory therapeutic effects on murine diabetic wound healing by modulating tissue inflammation, promoting collagen deposition and increasing vascularization in the neodermis. This HHC provided a viable strategy for diabetic wound dressing design.

Collagen-based hydrogels induce hyaline cartilage regeneration by immunomodulation and homeostasis maintenance.

Type I collagen (Col I) and hyaluronic acid (HA), derived from the extracellular matrix (ECM), have found widespread application in cartilage tissue engineering. Nevertheless, the potential of cell-free collagen-based scaffolds to induce in situ hyaline cartilage regeneration and the related mechanisms remain undisclosed. Here, we chose Col I and HA to construct Col I hydrogel and Col I-HA composite hydrogel with similar mechanical properties, denoted as Col and ColHA, respectively. Their potential to induce cartilage regeneration was investigated. The results revealed that collagen-based hydrogels could regenerate hyaline cartilage without any additional cells or growth factors. Notably, ColHA hydrogel stood out in this regard. It elicited a moderate activation, recruitment, and reprogramming of macrophages, thus efficiently mitigating local inflammation. Additionally, ColHA hydrogel enhanced stem cell recruitment, facilitated their chondrogenic differentiation, and inhibited chondrocyte fibrosis, hypertrophy, and catabolism, thereby preserving cartilage homeostasis. This study augments our comprehension of cartilage tissue induction theory by enriching immune-related mechanisms, offering innovative prospects for the design of cartilage defect repair scaffolds. STATEMENT OF SIGNIFICANCE: The limited self-regeneration ability and post-injury inflammation pose significant challenges to articular cartilage repair. Type I collagen (Col I) and hyaluronic acid (HA) are extensively used in cartilage tissue engineering. However, their specific roles in cartilage regeneration remain poorly understood. This study aimed to elucidate the functions of Col I and Col I-HA composite hydrogels (ColHA) in orchestrating inflammatory responses and promoting cartilage regeneration. ColHA effectively activated and recruited macrophages, reprogramming them from an M1 to an M2 phenotype, thus alleviating local inflammation. Additionally, ColHA facilitated stem cell homing, induced chondrogenesis, and concurrently inhibited fibrosis, hypertrophy, and catabolism, collectively contributing to the maintenance of cartilage homeostasis. These findings underscore the clinical potential of ColHA for repairing cartilage defects.

Advanced Wound Healing and Scar Reduction Using an Innovative Anti-ROS Polysaccharide Hydrogel with Recombinant Human Collagen Type III.

Excessive fibrotic scar formation during skin defect repair poses a formidable challenge, impeding the simultaneous acceleration of wound healing and prevention of scar formation and hindering the restoration of skin integrity and functionality. Drawing inspiration from the structural, compositional, and biological attributes of skin, we developed a hydrogel containing modified recombinant human collagen type III and thiolated hyaluronic acid to address the challenges of regenerating skin appendages and improving the recovery of skin functions after injury by reducing fibrotic scarring. The hydrogel displayed favorable biocompatibility, antioxidant properties, angiogenic potential, and fibroblast migration stimulation in vitro. In a rat full-layer defect model, it reduced inflammation, promoted microvascular formation, and significantly enhanced the wound healing speed and effectiveness. Additionally, by upregulating fibrosis-associated genes, such as TGFB1, it facilitated collagen accumulation and a beneficial balance between type I and type III collagen, potentially expediting skin regeneration and functional recovery. In conclusion, the utilization of rhCol III-HS demonstrated considerable potential as a wound dressing, offering a highly effective strategy for the restoration and rejuvenation of complete skin defects.

A Redox-Triggered Autophagy-Induced Nanoplatform with PD-L1 Inhibition for Enhancing Combined Chemo-Immunotherapy.

Epirubicin (EPI) alone can trigger mildly protective autophagy in residual tumor cells, resulting in an immunosuppressive microenvironment. This accelerates the recurrence of residual tumors and leads to antiprogrammed death ligand 1 (anti-PD-1)/PD-L1 therapy resistance, posing a significant clinical challenge in tumor immunotherapy. The combination of checkpoint inhibitors targeting the PD-1/PD-L1 pathway and amplifying autophagy presents an innovative approach to tumor treatment, which can prevent tumor immune escape and enhance therapeutic recognition. Herein, we aimed to synthesize a redox-triggered autophagy-induced nanoplatform with SA&EA-induced PD-L1 inhibition. The hyaluronic acid (HA) skeleton and arginine segment promoted active nanoplatform targeting, cell uptake, and penetration. The PLGLAG peptide was cleaved by overexpressing matrix metalloproteinase-2 (MMP-2) in the tumor microenvironment, and the PD-L1 inhibitor D-PPA was released to inhibit tumor immune escape. The intense autophagy inducers, STF-62247 and EPI, were released owing to the cleavage of disulfide bonds influenced by the high glutathione (GSH) concentration in tumor cells. The combination of EPI and STF induced apoptosis and autophagic cell death, effectively eliminating a majority of tumor cells. This indicated that the SA&EA nanoplatform has better therapeutic efficacy than the single STF@AHMPP and EPI@AHMPTP groups. This research provided a way to set up a redox-triggered autophagy-induced nanoplatform with PD-L1 inhibition to enhance chemo-immunotherapy.

Collagen-based hydrogels induce stem cell chondrogenesis and hyaline cartilage regeneration: an in vivo study.

Injectable, self-crosslinking collagen-based hydrogels are beneficial for chondrocytes to secrete matrix, positioning them as promising candidates for cartilage tissue engineering. However, previous studies lacked insight into the ability of cell-free collagen-based hydrogels to regenerate hyaline cartilage defect. Therefore, this study aimed to evaluate the potential of collagen-based hydrogels (Col and ColHA) to induce chondrogenic differentiation of stem cells and in situ hyaline cartilage regeneration. Both Col and ColHA hydrogels self-crosslinked in situ and exhibited similar physical properties. In vitro experiments showed they supported the survival, adhesion, spreading, and proliferation of bone marrow stem cells (BMSCs). Moreover, both hydrogels induced ectopic differentiation of BMSCs into chondrocytes when implanted subcutaneously into the back of nude mice. ColHA hydrogel notably enhanced type II collagen secretion. The results of repairing cartilage defects in situ revealed both hydrogels facilitated hyaline cartilage regeneration and maintained cartilage phenotype without exogenous BMSCs. Hydrogels encapsulating BMSCs expedited cartilage repair, and ColHA/BMSC constructs showed better mechanical properties, suggesting their potential for cartilage repair applications. This study implies that collagen-based hydrogels are good candidates for hyaline cartilage regeneration.