Biomaterials to Mimic and Heal Connective Tissues

Use of a pH-responsive imatinib mesylate sustained-release hydrogel for the treatment of tendon adhesion by inhibiting PDGFRβ/CLDN1 pathway

Adhesion after tendon injury, which can result in limb movement disorders, is a common clinical complication; however, effective treatment methods are lacking. Hyaluronic acid hydrogels are a new biomedical material used to prevent tendon adhesion owing to their good biocompatibility. In addition, potential drugs that inhibit adhesion formation have gradually been discovered. The anti-adhesion effects of a combination of loaded drugs into hydrogels have become an emerging trend. However, current drug delivery systems usually lack specific regulation of drug release, and the effectiveness of drugs for treating tendon adhesions is mostly flawed. In this study, we identified a new drug, imatinib mesylate (IM), that prevents tendon adhesion and explored its related molecular pathways. In addition, we designed a pH-responsive sustained-release hydrogel for delivery. Using the metal-organic framework ZIF-8 as a drug carrier, we achieved controlled drug release to increase the effective drug dose at the peak of adhesion formation to achieve better therapeutic effects. The results showed that IM blocked the formation of peritendon adhesions by inhibiting the PDGFRβ/ERK/STAT3/CLDN1 pathway. Furthermore, the hydrogel with ZIF-8 exhibited better physical properties and drug release curves than the hydrogel loaded only with drugs, showing better prevention and treatment effects on tendon adhesion.

Stem-Cell-Driven Chondrogenesis: Perspectives on Amnion-Derived Cells

Regenerative medicine harnesses stem cells' capacity to restore damaged tissues and organs. In vitro methods employing specific bioactive molecules, such as growth factors, bio-inductive scaffolds, 3D cultures, co-cultures, and mechanical stimuli, steer stem cells toward the desired differentiation pathways, mimicking their natural development. Chondrogenesis presents a challenge for regenerative medicine. This intricate process involves precise modulation of chondro-related transcription factors and pathways, critical for generating cartilage. Cartilage damage disrupts this process, impeding proper tissue healing due to its unique mechanical and anatomical characteristics. Consequently, the resultant tissue often forms fibrocartilage, which lacks adequate mechanical properties, posing a significant hurdle for effective regeneration. This review comprehensively explores studies showcasing the potential of amniotic mesenchymal stem cells (AMSCs) and amniotic epithelial cells (AECs) in chondrogenic differentiation. These cells exhibit innate characteristics that position them as promising candidates for regenerative medicine. Their capacity to differentiate toward chondrocytes offers a pathway for developing effective regenerative protocols. Understanding and leveraging the innate properties of AMSCs and AECs hold promise in addressing the challenges associated with cartilage repair, potentially offering superior outcomes in tissue regeneration.

PM2.5, component cause of severe metabolically abnormal obesity: An in silico, observational and analytical study

Obesity is currently one of the most alarming pathological conditions due to the progressive increase in its prevalence. In the last decade, it has been associated with fine particulate matter suspended in the air (PM2.5). The purpose of this study was to explore the mechanistic interaction of PM2.5 with a high-fat diet (HFD) through the differential regulation of transcriptional signatures, aiming to identify the association of these particles with metabolically abnormal obesity. The research design was observational, using bioinformatic methods and an explanatory approach based on Rothman's causal model. We propose three new transcriptional signatures in murine adipose tissue. The sum of transcriptional differences between the group exposed to an HFD and PM2.5, compared to the control group, were 0.851, 0.265, and -0.047 (p > 0.05). The HFD group increased body mass by 20% with two positive biomarkers of metabolic impact. The group exposed to PM2.5 maintained a similar weight to the control group but exhibited three positive biomarkers. Enriched biological pathways (p < 0.05) included PPAR signaling, small molecule transport, adipogenesis genes, cytokine-cytokine receptor interaction, and HIF-1 signaling. Transcriptional regulation predictions revealed CpG islands and common transcription factors. We propose three new transcriptional signatures: FAT-PM2.5-CEJUS, FAT-PM2.5-UP, and FAT-PM2.5-DN, whose transcriptional regulation profile in adipocytes was statistically similar by dietary intake and HFD and exposure to PM2.5 in mice; suggesting a mechanistic interaction between both factors. However, HFD-exposed murines developed moderate metabolically abnormal obesity, and PM2.5-exposed murines developed severe abnormal metabolism without obesity. Therefore, in Rothman's terms, it is concluded that HFD is a sufficient cause of the development of obesity, and PM2.5 is a component cause of severe abnormal metabolism of obesity. These signatures would be integrated into a systemic biological process that would induce transcriptional regulation in trans, activating obesogenic biological pathways, restricting lipid mobilization pathways, decreasing adaptive thermogenesis and angiogenesis, and altering vascular tone thus inducing a severe metabolically abnormal obesity.

Janus Membranes Patch Achieves High-Quality Tendon Repair: Inhibiting Exogenous Healing and Promoting Endogenous Healing

The imbalance between endogenous and exogenous healing is the fundamental reason for the poor tendon healing. In this study, a Janus patch was developed to promote endogenous healing and inhibit exogenous healing, leading to improved tendon repair. The upper layer of the patch is a poly(dl-lactide-co-glycolide)/polycaprolactone (PLGA/PCL) nanomembrane (PMCP-NM) modified with poly(2-methylacryloxyethyl phosphocholine) (PMPC), which created a lubricated and antifouling surface, preventing cell invasion and mechanical activation. The lower layer is a PLGA/PCL fiber membrane loaded with fibrin (Fb) (Fb-NM), serving as a temporary chemotactic scaffold to regulate the regenerative microenvironment. In vitro, the Janus patch effectively reduced 92.41% cell adhesion and 79.89% motion friction. In vivo, the patch inhibited tendon adhesion through the TGF-β/Smad signaling pathway and promoted tendon maturation. This Janus patch is expected to provide a practical basis and theoretical guidance for high-quality soft tissue repair.

Biomaterial engineering for cell transplantation

The current paradigm of medicine is mostly designed to block or prevent pathological events. Once the disease-led tissue damage occurs, the limited endogenous regeneration may lead to depletion or loss of function for cells in the tissues. Cell therapy is rapidly evolving and influencing the field of medicine, where in some instances attempts to address cell loss in the body. Due to their biological function, engineerability, and their responsiveness to stimuli, cells are ideal candidates for therapeutic applications in many cases. Such promise is yet to be fully obtained as delivery of cells that functionally integrate with the desired tissues upon transplantation is still a topic of scientific research and development. Main known impediments for cell therapy include mechanical insults, cell viability, host's immune response, and lack of required nutrients for the transplanted cells. These challenges could be divided into three different steps: 1) Prior to, 2) during the and 3) after the transplantation procedure. In this review, we attempt to briefly summarize published approaches employing biomaterials to mitigate the above technical challenges. Biomaterials are offering an engineerable platform that could be tuned for different classes of cell transplantation to potentially enhance and lengthen the pharmacodynamics of cell therapies.

Biofabrication Strategies for Oral Soft Tissue Regeneration

Gingival recession, a prevalent condition affecting the gum tissues, is characterized by the exposure of tooth root surfaces due to the displacement of the gingival margin. This review explores conventional treatments, highlighting their limitations and the quest for innovative alternatives. Importantly, it emphasizes the critical considerations in gingival tissue engineering leveraging on cells, biomaterials, and signaling factors. Successful tissue-engineered gingival constructs hinge on strategic choices such as cell sources, scaffold design, mechanical properties, and growth factor delivery. Unveiling advancements in recent biofabrication technologies like 3D bioprinting, electrospinning, and microfluidic organ-on-chip systems, this review elucidates their precise control over cell arrangement, biomaterials, and signaling cues. These technologies empower the recapitulation of microphysiological features, enabling the development of gingival constructs that closely emulate the anatomical, physiological, and functional characteristics of native gingival tissues. The review explores diverse engineering strategies aiming at the biofabrication of realistic tissue-engineered gingival grafts. Further, the parallels between the skin and gingival tissues are highlighted, exploring the potential transfer of biofabrication approaches from skin tissue regeneration to gingival tissue engineering. To conclude, the exploration of innovative biofabrication technologies for gingival tissues and inspiration drawn from skin tissue engineering look forward to a transformative era in regenerative dentistry with improved clinical outcomes.

Challenges and opportunities of medicines for treating tendon inflammation and fibrosis: A comprehensive and mechanistic review

BACKGROUND

Tendinopathy refers to conditions characterized by collagen degeneration within tendon tissue, accompanied by the proliferation of capillaries and arteries, resulting in reduced mechanical function, pain, and swelling. While inflammation in tendinopathy can play a role in preventing infection, uncontrolled inflammation can hinder tissue regeneration and lead to fibrosis and impaired movement.

OBJECTIVES

The inability to regulate inflammation poses a significant limitation in tendinopathy treatment. Therefore, an ideal treatment strategy should involve modulation of the inflammatory process while promoting tissue regeneration.

METHODS

The current review article was prepared by searching PubMed, Scopus, Web of Science, and Google Scholar databases. Several treatment approaches based on biomaterials have been developed.

RESULTS

This review examines various treatment methods utilizing small molecules, biological compounds, herbal medicine-inspired approaches, immunotherapy, gene therapy, cell-based therapy, tissue engineering, nanotechnology, and phototherapy.

CONCLUSION

These treatments work through mechanisms of action involving signaling pathways such as transforming growth factor-beta (TGF-β), mitogen-activated protein kinases (MAPKs), and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), all of which contribute to the repair of injured tendons.

X-Ray Visible Protein Scaffolds by Bulk Iodination

Protein-based biomaterial use is expanding within medicine, together with the demand to visualize their placement and behavior in vivo. However, current medical imaging techniques struggle to differentiate between protein-based implants and surrounding tissue. Here a fast, simple, and translational solution for tracking transplanted protein-based scaffolds is presented using X-ray CT-facilitating long-term, non-invasive, and high-resolution imaging. X-ray visible scaffolds are engineered by selectively iodinating tyrosine residues under mild conditions using readily available reagents. To illustrate translatability, a clinically approved hernia repair mesh (based on decellularized porcine dermis) is labeled, preserving morphological and mechanical properties. In a mouse model of mesh implantation, implants retain marked X-ray contrast up to 3 months, together with an unchanged degradation rate and inflammatory response. The technique's compatibility is demonstrated with a range of therapeutically relevant protein formats including bovine, porcine, and jellyfish collagen, as well as silk sutures, enabling a wide range of surgical and regenerative medicine uses. This solution tackles the challenge of visualizing implanted protein-based biomaterials, which conventional imaging methods fail to differentiate from endogenous tissue. This will address previously unanswered questions regarding the accuracy of implantation, degradation rate, migration, and structural integrity, thereby accelerating optimization and safe translation of therapeutic biomaterials.

Effect of Functionalization of Texturized Polypropylene Surface by Silanization and HBII-RGD Attachment on Response of Primary Abdominal and Vaginal Fibroblasts

Soft tissue defects, such as incisional hernia or pelvic organ prolapse, are prevalent pathologies characterized by a tissue microenvironment rich in fragile and dysfunctional fibroblasts. Precision medicine could improve their surgical repair, currently based on polymeric materials. Nonetheless, biomaterial-triggered interventions need first a better understanding of the cell-material interfaces that truly consider the patients' biology. Few tools are available to study the interactions between polymers and dysfunctional soft tissue cells in vitro. Here, we propose polypropylene (PP) as a matrix to create microscale surfaces w/wo functionalization with an HBII-RGD molecule, a fibronectin fragment modified to include an RGD sequence for promoting cell attachment and differentiation. Metal mold surfaces were roughened by shot blasting with aluminum oxide, and polypropylene plates were obtained by injection molding. HBII-RGD was covalently attached by silanization. As a proof of concept, primary abdominal and vaginal wall fasciae fibroblasts from control patients were grown on the new surfaces. Tissue-specific significant differences in cell morphology, early adhesion and cytoskeletal structure were observed. Roughness and biofunctionalization parameters exerted unique and combinatorial effects that need further investigation. We conclude that the proposed model is effective and provides a new framework to inform the design of smart materials for the treatment of clinically compromised tissues.

Instant tough adhesion of polymer networks

Generating strong rapid adhesion between hydrogels has the potential to advance the capabilities of modern medicine and surgery. Current hydrogel adhesion technologies rely primarily on liquid-based diffusion mechanisms and the formation of covalent bonds, requiring prolonged time to generate adhesion. Here, we present a simple and versatile strategy using dry chitosan polymer films to generate instant adhesion between hydrogel-hydrogel and hydrogel-elastomer surfaces. Using this approach we can achieve extremely high adhesive energies (>3,000 J/m2), which are governed by pH change and non-covalent interactions including H-bonding, Van der Waals forces, and bridging polymer entanglement. Potential examples of biomedical applications are presented, including local tissue cooling, vascular sealing, prevention of surgical adhesions, and prevention of hydrogel dehydration. We expect these findings and the simplicity of this approach to have broad implications for adhesion strategies and hydrogel design.

Highly oriented hydrogels for tissue regeneration: design strategies, cellular mechanisms, and biomedical applications

Many human tissues exhibit a highly oriented architecture that confers them with distinct mechanical properties, enabling adaptation to diverse and challenging environments. Hydrogels, with their water-rich "soft and wet" structure, have emerged as promising biomimetic materials in tissue engineering for repairing and replacing damaged tissues and organs. Highly oriented hydrogels can especially emulate the structural orientation found in human tissue, exhibiting unique physiological functions and properties absent in traditional homogeneous isotropic hydrogels. The design and preparation of highly oriented hydrogels involve strategies like including hydrogels with highly oriented nanofillers, polymer-chain networks, void channels, and microfabricated structures. Understanding the specific mechanism of action of how these highly oriented hydrogels affect cell behavior and their biological applications for repairing highly oriented tissues such as the cornea, skin, skeletal muscle, tendon, ligament, cartilage, bone, blood vessels, heart, etc., requires further exploration and generalization. Therefore, this review aims to fill that gap by focusing on the design strategy of highly oriented hydrogels and their application in the field of tissue engineering. Furthermore, we provide a detailed discussion on the application of highly oriented hydrogels in various tissues and organs and the mechanisms through which highly oriented structures influence cell behavior.

Effectiveness of a New Enzyme-Free Method for the Preparation of a Decellularized Adipose-Derived Matrix

BACKGROUND

Decellularized adipose-derived matrix (DAM) represents a new alternative to tissue fillers. The function of DAM is closely associated with the decellularization technique used for its preparation. However, most techniques are time-consuming and expensive, and this might reduce the popularity of DAM.

OBJECTIVES

The study aimed to investigate an enzyme-free adipose decellularization method and generate a DAM capable of adipose tissue regeneration.

METHODS

DAMs prepared by the enzyme-free and Flynn's methods were compared and co-cultured with human adipose-derived stem cells (hADSCs) to investigate cytocompatibility. Adipose tissue formation was evaluated by injecting the DAMs into the backs of nude mice over 4 weeks. Samples were harvested for gross and perilipin immunohistochemistry analysis at 1 and 4 weeks.

RESULTS

The enzyme-free method is effective for adipose decellularization because it removes adipocytes and preserves the microstructure. In vitro, the DAM made by the enzyme-free method could support the attachment, growth, proliferation, and differentiation of hADSCs, and promote the enhanced secretion of vascular endothelial growth factor by hADSCs; this DAM also induced the formation and maturity of adipocytes in vivo.

CONCLUSIONS

This study describes a highly effective enzyme-free method for adipose tissue decellularization that also promotes adipocyte formation and adipose tissue volume stability in vitro and in vivo, resulting in a new alternative tissue filler.

Mesenchymal Stem Cell-Derived Exosomes in Various Chronic Liver Diseases: Hype or Hope?

Chronic liver conditions are associated with high mortality rates and have a large adverse effect on human well-being as well as a significant financial burden. Currently, the only effective treatment available for the effects of liver failure and cirrhosis resulting from the progression of several chronic liver diseases is liver transplantation carried out at the original location. This implies that developing novel and effective treatments is imperative. Regenerative medicine has long been associated with stem cell therapy. Mesenchymal stem cells (MSCs), a type of cell with great differentiation potential, have become the preferred source for stem cell therapy. According to recent studies, MSCs' paracrine products-rather than their capacity for differentiation-play a significant therapeutic effect. MSC exosomes, a type of extracellular vesicle (MSC-EV), came into view as the paracrine substances of MSCs. According to research, MSC exosomes can maintain tissue homeostasis, which is necessary for healthy tissue function. All tissues contain them, and they take part in a variety of biological activities that support cellular activity and tissue regeneration in order to preserve tissue homeostasis. The outcomes support the use of MSCs and the exosomes they produce as a therapeutic option for a range of diseases. This review provides a brief overview of the source of MSC-EVs and outlines their physiological roles and biochemical capabilities. The elucidation of the role of MSC-EVs in the recovery and repair of hepatic tissues, as well as their contribution to maintaining tissue homeostasis, is discussed in relation to different chronic liver diseases. This review aims to provide new insights into the unique roles that MSC-EVs play in the treatment of chronic liver diseases.

Synthetic Collagen Hydrogels through Symmetric Self-Assembly of Small Peptides

Animal-sourced hydrogels, such as collagen, are widely used as extracellular-matrix (ECM) mimics in tissue engineering but are plagued with problems of reproducibility, immunogenicity, and contamination. Synthetic, chemically defined hydrogels can avoid such issues. Despite the abundance of collagen in the ECM, synthetic collagen hydrogels are extremely rare due to design challenges brought on by the triple-helical structure of collagen. Sticky-ended symmetric self-assembly (SESSA) overcomes these challenges by maximizing interactions between the strands of the triple helix, allowing the assembly of collagen-mimetic peptides (CMPs) into robust synthetic collagen nanofibers. This optimization, however, also minimizes interfiber contacts. In this work, symmetric association states for the SESSA of short CMPs to probe their increased propensity for interfiber association are modelled. It is found that 33-residue CMPs not only self-assemble through sticky ends, but also form hydrogels. These self-assemblies behave with remarkable consistency across multiple scales and present a clear link between their triple-helical architecture and the properties of their hydrogels. The results show that SESSA is an effective and robust design methodology that enables the rational design of synthetic collagen hydrogels.

Micro-nano hierarchical scaffold providing temporal-matched biological constraints for tendon reconstruction

Due to the limitations of tendon biology, high-quality tendon repair remains a clinical and scientific challenge. Here, a micro-nano hierarchical scaffold is developed to promote orderly tendon regeneration by providing temporal-matched biological constraints. In short, fibrin (Fb), which provides biological constraints, is loaded into poly (DL-lactide-co-glycolide) nanoyarns with suitable degradation cycles (Fb-loaded nanofiber yarns (Fb-NY)). Then further combined with braiding technology, temporary chemotactic Fb scaffolds with tendon extracellular matrix-like structures are obtained to initiate the regeneration process. At the early stage of healing (2 w), the regeneration microenvironment is regulated (inducing M2 macrophages and restoring the early blood supply necessary for healing) by Fb, and the alignment of cells and collagen is induced by nanoyarn. At the late healing stage (8 w), with the degradation of Fb-NY, non-functional vascular regression occurs, and the newborn tissues gradually undergo load-bearing remodeling, restoring the anvascularous and ordered structure of the tendon. In summary, the proposed repair strategy provides temporal-matched biological constraints, offering a potential pathway to reconstruct the ordered structure and function of tendons.

Hydroxyapatite: A journey from biomaterials to advanced functional materials

Hydroxyapatite (HAp), a well-known biomaterial, has witnessed a remarkable evolution over the years, transforming from a simple biocompatible substance to an advanced functional material with a wide range of applications. This abstract provides an overview of the significant advancements in the field of HAp and its journey towards becoming a multifunctional material. Initially recognized for its exceptional biocompatibility and bioactivity, HAp gained prominence in the field of bone tissue engineering and dental applications. Its ability to integrate with surrounding tissues, promote cellular adhesion, and facilitate osseointegration made it an ideal candidate for various biomedical implants and coatings. As the understanding of HAp grew, researchers explored its potential beyond traditional biomaterial applications. With advances in material synthesis and engineering, HAp began to exhibit unique properties that extended its utility to other disciplines. Researchers successfully tailored the composition, morphology, and surface characteristics of HAp, leading to enhanced mechanical strength, controlled drug release capabilities, and improved biodegradability. These modifications enabled the utilization of HAp in drug delivery systems, biosensors, tissue engineering scaffolds, and regenerative medicine applications. Moreover, the exceptional biomineralization properties of HAp allowed for the incorporation of functional ions and molecules during synthesis, leading to the development of bioactive coatings and composites with specific therapeutic functionalities. These functionalized HAp materials have demonstrated promising results in antimicrobial coatings, controlled release systems for growth factors and therapeutic agents, and even as catalysts in chemical reactions. In recent years, HAp nanoparticles and nanostructured materials have emerged as a focal point of research due to their unique physicochemical properties and potential for targeted drug delivery, imaging, and theranostic applications. The ability to manipulate the size, shape, and surface chemistry of HAp at the nanoscale has paved the way for innovative approaches in personalized medicine and regenerative therapies. This abstract highlights the exceptional evolution of HAp, from a traditional biomaterial to an advanced functional material. The exploration of novel synthesis methods, surface modifications, and nanoengineering techniques has expanded the horizon of HAp applications, enabling its integration into diverse fields ranging from biomedicine to catalysis. Additionally, this manuscript discusses the emerging prospects of HAp-based materials in photocatalysis, sensing, and energy storage, showcasing its potential as an advanced functional material beyond the realm of biomedical applications. As research in this field progresses, the future holds tremendous potential for HAp-based materials to revolutionize medical treatments and contribute to the advancement of science and technology.

A photoactivatable and phenylboronic acid-functionalized nanoassembly for combating multidrug-resistant gram-negative bacteria and their biofilms

Background

Multidrug-resistant (MDR) gram-negative bacteria-related infectious diseases have caused an increase in the public health burden and mortality. Moreover, the formation of biofilms makes these bacteria difficult to control. Therefore, developing novel interventions to combat MDR gram-negative bacteria and their biofilms-related infections are urgently needed. The purpose of this study was to develop a multifunctional nanoassembly (IRNB) based on IR-780 and N, N'-di-sec-butyl-N, N'- dinitroso-1,4-phenylenediamine (BNN6) for synergistic effect on the infected wounds and subcutaneous abscesses caused by gram-negative bacteria.

Methods

The characterization and bacteria-targeting ability of IRNB were investigated. The bactericidal efficacy of IRNB against gram-negative bacteria and their biofilms was demonstrated by crystal violet staining assay, plate counting method and live/dead staining in vitro. The antibacterial efficiency of IRNB was examined on a subcutaneous abscess and cutaneous infected wound model in vivo. A cell counting kit-8 assay, Calcein/PI cytotoxicity assay, hemolysis assay and intravenous injection assay were performed to detect the biocompatibility of IRNB in vitro and in vivo.

Results

Herein, we successfully developed a multifunctional nanoassembly IRNB based on IR-780 and BNN6 for synergistic photothermal therapy (PTT), photodynamic therapy (PDT) and nitric oxide (NO) effect triggered by an 808 nm laser. This nanoassembly could accumulate specifically at the infected sites of MDR gram-negative bacteria and their biofilms via the covalent coupling effect. Upon irradiation with an 808 nm laser, IRNB was activated and produced both reactive oxygen species (ROS) and hyperthermia. The local hyperthermia could induce NO generation, which further reacted with ROS to generate ONOO-, leading to the enhancement of bactericidal efficacy. Furthermore, NO and ONOO- could disrupt the cell membrane, which converts bacteria to an extremely susceptible state and further enhances the photothermal effect. In this study, IRNB showed a superior photothermal-photodynamic-chemo (NO) synergistic therapeutic effect on the infected wounds and subcutaneous abscesses caused by gram-negative bacteria. This resulted in effective control of associated infections, relief of inflammation, promotion of re-epithelization and collagen deposition, and regulation of angiogenesis during wound healing. Moreover, IRNB exhibited excellent biocompatibility, both in vitro and in vivo.

Conclusions

The present research suggests that IRNB can be considered a promising alternative for treating infections caused by MDR gram-negative bacteria and their biofilms.

Vascular endothelial growth factor a modified mRNA engineered cellular electrospun membrane complexes promotes mouse skin wound repair

Artificial skin substitutes are one of the most promising areas of wound healing research; however, graft survival largely depends on how the treatment is performed. Early angiogenesis is essential for wound healing and graft survival and vascular endothelial growth factor A (VEGFA) is an important cytokine that stimulates angiogenesis. Here, we first investigated the effects of different ratios of collagen (BC) and gelatin blended with poly (l-lactide-co-caprolactone) (PLCL) on nanofibrous membranes. The Young's modulus and cell proliferation were significantly higher in the 50% BC group than that in all other groups. Then, cellular electrospun membrane complexes (CEMC) were successfully constructed from nanoscaffolds and fibroblasts extracted from human foreskin and engineered with controlled autocrine VEGFA by transfecting VEGFA modified mRNA (modRNA). Engineered CEMC significantly promoted wound healing in vivo and contributed to stable vascular network formation in the grafted area, thereby increasing the survival rate of the engineered skin. This study provides a potential solution for wound healing while establishing the value of different RNA modification methods for various engineered skins in the future, thereby advancing engineered skin development.

Multifilament Collagen Fiber Bundles with Tendon-like Structure and Mechanical Performance

Collagen multifilament bundles comprised of thousands of monofilaments are prepared by multipin contact drawing of an entangled polymer solution consisting of collagen and poly(ethylene oxide) (PEO). The multifilament bundles are hydrated in graded concentrations of PEO and phosphate buffered saline (PBS) to promote assembly of collagen fibrils within each monofilament while preserving the structure of the multifilament bundle. Multiscale structural characterization reveals that the hydrated multifilament bundle contains properly folded collagen molecules packed in collagen fibrils containing microfibrils, staggered by exactly one-sixth of the microfibril D-band spacing to produce a periodicity of 11 nm. Sequence analysis predicts that in this structure, phenylalanine residues are close enough within and between microfibrils to become ultraviolet C (UVC) crosslinked. In agreement with this analysis, the ultimate tensile strength (UTS) and Young's modulus of the hydrated collagen multifilament bundles crosslinked by UVC radiation increase nonlinearly with total UVC energy to reach values in the range of native tendons without damage to the collagen molecules. This fabrication method recapitulates the structure of a tendon across multiple length scales and offers tunability in tensile properties using only collagen molecules and no other chemical additives in addition to PEO, which is almost entirely removed during the hydration process.

Hierarchical helical carbon nanotube fibre as a bone-integrating anterior cruciate ligament replacement

High rates of ligament damage require replacements; however, current synthetic materials have issues with bone integration leading to implant failure. Here we introduce an artificial ligament that has the required mechanical properties and can integrate with the host bone and restore movement in animals. The ligament is assembled from aligned carbon nanotubes formed into hierarchical helical fibres bearing nanometre and micrometre channels. Osseointegration of the artificial ligament is observed in an anterior cruciate ligament replacement model where clinical polymer controls showed bone resorption. A higher pull-out force is found after a 13-week implantation in rabbit and ovine models, and animals can run and jump normally. The long-term safety of the artificial ligament is demonstrated, and the pathways involved in integration are studied.

Emerging Bioprinting for Wound Healing

Bioprinting has attracted much attention due to its suitability for fabricating biomedical devices. In particular, bioprinting has become one of the growing centers in the field of wound healing, with various types of bioprinted devices being developed, including 3D scaffolds, microneedle patches, and flexible electronics. Bioprinted devices can be designed with specific biostructures and biofunctions that closely match the shape of wound sites and accelerate the regeneration of skin through various approaches. Herein, a comprehensive review of the bioprinting of smart wound dressings is presented, emphasizing the crucial effect of bioprinting in determining biostructures and biofunctions. The review begins with an overview of bioprinting techniques and bioprinted devices, followed with an in-depth discussion of polymer-based inks, modification strategies, additive ingredients, properties, and applications. The strategies for the modification of bioprinted devices are divided into seven categories, including chemical synthesis of novel inks, physical blending, coaxial bioprinting, multimaterial bioprinting, physical absorption, chemical immobilization, and hybridization with living cells, and examples are presented. Thereafter, the frontiers of bioprinting and wound healing, including 4D bioprinting, artificial intelligence-assisted bioprinting, and in situ bioprinting, are discussed from a perspective of interdisciplinary sciences. Finally, the current challenges and future prospects in this field are highlighted.

Xonotlite Nanowire-Containing Bioactive Scaffolds for the Therapy of Defective Adipose Tissue in Breast Cancer

Considering the challenge in the treatment of severe breast tumor patients, xonotlite nanowire-containing bioactive scaffolds (Fe3O4-CS-GelMA) were fabricated by the 3D-printing technique for the therapy of injured adipose tissue after surgery. Importantly, benefiting from the excellent magnetothermal performance of Fe3O4 microspheres, Fe3O4-CS-GelMA scaffolds could effectively kill tumor cells in vitro and suppress breast cancer in vivo under an alternating magnetic field, and the tumor did not recur in 2 weeks. In addition, attributed to the released bioactive inorganic ions, Fe3O4-CS-GelMA composite scaffolds could effectively promote the expression of adipogenesis-related genes and proteins of adipose-derived stem cells (ADSCs) via the PI3K-AKT signaling pathway in vitro. Furthermore, Fe3O4-CS-GelMA scaffolds with ADSCs could obviously stimulate the formation of adipose in vivo, compared with that of pure GelMA without inorganic components. Therefore, this study offers a promising strategy for the therapy of breast tumors after the surgical excision of breast carcinoma.

Biomimetic tri-layered small-diameter vascular grafts with decellularized extracellular matrix promoting vascular regeneration and inhibiting thrombosis with the salidroside

Small-diameter vascular grafts (SDVGs) are urgently required for clinical applications. Constructing vascular grafts mimicking the defining features of native arteries is a promising strategy. Here, we constructed a tri-layered vascular graft with a native artery decellularized extracellular matrix (dECM) mimicking the component of arteries. The porcine thoracic aorta was decellularized and milled into dECM powders from the differential layers. The intima and media dECM powders were blended with poly (L-lactide-co-caprolactone) (PLCL) as the inner and middle layers of electrospun vascular grafts, respectively. Pure PLCL was electrospun as a strengthening sheath for the outer layer. Salidroside was loaded into the inner layer of vascular grafts to inhibit thrombus formation. In vitro studies demonstrated that dECM provided a bioactive milieu for human umbilical vein endothelial cell (HUVEC) extension adhesion, proliferation, migration, and tube-forming. The in vivo studies showed that the addition of dECM could promote endothelialization, smooth muscle regeneration, and extracellular matrix deposition. The salidroside could inhibit thrombosis. Our study mimicked the component of the native artery and combined it with the advantages of synthetic polymer and dECM which provided a promising strategy for the design and construction of SDVGs.

Breakthrough treatments for accelerated wound healing

Skin injuries across the body continue to disrupt everyday life for millions of patients and result in prolonged hospital stays, infection, and death. Advances in wound healing devices have improved clinical practice but have mainly focused on treating macroscale healing versus underlying microscale pathophysiology. Consensus is lacking on optimal treatment strategies using a spectrum of wound healing products, which has motivated the design of new therapies. We summarize advances in the development of novel drug, biologic products, and biomaterial therapies for wound healing for marketed therapies and those in clinical trials. We also share perspectives for successful and accelerated translation of novel integrated therapies for wound healing.

Dual-Function Hydrogel Dressings with a Dynamic Exchange of Iron Ions and an Antibiotic Drug for Treatment of Infected Wounds

Bacterial infection is a major problem with diabetic wounds that may result in nonhealing chronic ulcers. Here, we report an approach to antibacterial hydrogel dressings for enhanced treatment of infected skin wounds. A fibrous hydrogel was derived from cellulose nanocrystals that were modified with dopamine and cross-linked with gelatin. The hydrogel was loaded with gentamicin, an antibiotic drug. Enhanced antibacterial hydrogel performance resulted from (i) a highly specific sequestration of Fe³⁺ ions (much needed by bacteria) from the wound exudate and (ii) a dynamic exchange between gentamicin released from the hydrogel and Fe³⁺ ions withdrawn from the wound exudate. Such exchange was possible due to the high value of the binding constant of Fe³⁺ ions to dopamine. The hydrogel did not affect the metabolic activity of skin-related cells and showed enhanced antibacterial performance against common wound pathogens such as S. aureus and P. aeruginosa. Furthermore, it promoted healing of infected diabetic wounds due to a synergistic antibacterial effect providing the dynamic exchange between Fe³⁺ ions and gentamicin. This work provides a strategy for the design of dual-function wound dressings, with both starving and killing bacteria and enhanced wound healing performance.

Substrate viscoelasticity affects human macrophage morphology and phagocytosis

Viscoelasticity is an inherent characteristic of many living tissues and, in an attempt to better recapitulate this aspect in cell culture, hydrogel biomaterials have been engineered to exhibit time-dependent energy-dissipative mechanical behavior. Viscoelastic hydrogel culture platforms have been instrumental in understanding the biological effects of viscoelasticity. Although viscoelasticity has been shown to regulate fundamental cell processes such as spreading and differentiation in adherent cells, the influence of viscoelasticity on macrophage behavior has not been explored. Here, we use a tunable viscoelastic polyacrylamide hydrogel culture system to demonstrate that viscoelasticity is an important biophysical regulator of macrophage function. After biologically validating our system with HS-5 fibroblasts to show behavior consistent with existing reports, we seed human THP-1 monocytes on these viscoelastic substrates and differentiate them into macrophages. THP-1 macrophages become smaller and rounder, and less efficient at phagocytosis on more viscous polyacrylamide hydrogel substrates. Since macrophages play key roles in mounting responses such as inflammation and fibrosis, these results indicate that viscoelasticity is an important parameter in the design of immunomodulatory biomaterials.

Alginate-based biomaterial-mediated regulation of macrophages in bone tissue engineering

Many studies in the bone tissue engineering field have focused on the interactions between materials and bone marrow stem cells. With the development of osteoimmunology, the immune cells' essential role in biomaterial-mediated osteogenesis has increasingly been recognized. As a promising therapeutic candidate for bone defects due to their prominent biocompatibility, tuneability, and versatility, it is necessary to develop alginate-based biomaterials that can regulate immune cells, especially macrophages. Moreover, modified alginate-based biomaterials may facilitate better regulation of macrophage phenotypes by the newly endowed physicochemical properties, including stiffness, porosity, hydrophilicity, and electrical properties. This review summarizes the role of macrophages in bone regeneration and the recent research progress related to the effects of alginate-based biomaterials on macrophages applied in bone tissue engineering. This review also emphasizes the strategies adopted by material design to regulate macrophage phenotypes, the corresponding macrophage responses, and their contribution to osteogenesis.

Development of a Nanohybrid Peptide Hydrogel for Enhanced Intervertebral Disc Repair and Regeneration

Effective therapeutic approaches to overcome the heterogeneous pro-inflammatory and inhibitory extracellular matrix (ECM) microenvironment are urgently needed to achieve robust structural and functional repair of severely wounded fibrocartilaginous tissues. Herein we developed a dynamic and multifunctional nanohybrid peptide hydrogel (NHPH) through hierarchical self-assembly of peptide amphiphile modified with biodegradable two-dimensional nanomaterials with enzyme-like functions. NHPH is not only injectable, biocompatible, and biodegradable but also therapeutic by catalyzing the scavenging of pro-inflammatory reactive oxygen species and promoting ECM remodeling. In addition, our NHPH method facilitated the structural and functional recovery of the intervertebral disc (IVD) after severe injuries by delivering pro-regenerative cytokines in a sustained manner, effectively suppressing immune responses and eventually restoring the regenerative microenvironment of the ECM. In parallel, the NHPH-enhanced nucleus pulposus cell differentiation and pain reduction in a rat nucleotomy model further validated the therapeutic potential of NHPH. Collectively, our advanced nanoscaffold technology will provide an alternative approach for the effective treatment of IVD degeneration as well as other fibrocartilaginous tissue injuries.

Applications of functionally-adapted hydrogels in tendon repair

Despite all the efforts made in tissue engineering for tendon repair, the management of tendon injuries still poses a challenge, as current treatments are unable to restore the function of tendons following injuries. Hydrogels, due to their exceptional biocompatibility and plasticity, have been extensively applied and regarded as promising candidate biomaterials in tissue regeneration. Varieties of approaches have designed functionally-adapted hydrogels and combined hydrogels with other factors (e.g., bioactive molecules or drugs) or materials for the enhancement of tendon repair. This review first summarized the current state of knowledge on the mechanisms underlying the process of tendon healing. Afterward, we discussed novel strategies in fabricating hydrogels to overcome the issues frequently encountered during the applications in tendon repair, including poor mechanical properties and undesirable degradation. In addition, we comprehensively summarized the rational design of hydrogels for promoting stem-cell-based tendon tissue engineering via altering biophysical and biochemical factors. Finally, the role of macrophages in tendon repair and how they respond to immunomodulatory hydrogels were highlighted.

Physico-biological evaluation of 3D printed dECM/TOCN/alginate hydrogel based scaffolds for cartilage tissue regeneration

Cartilage damage is the leading cause of osteoarthritis (OA), especially in an aging society. Mimicking the native cartilage microenvironment for chondrogenic differentiation along with constructing a stable and controlled architectural scaffold is considerably challenging. In this study, three-dimensional (3D) printed scaffolds using tempo-oxidized cellulose nanofiber (TOCN), decellularized extracellular matrix (dECM), and sodium alginate (SA) were fabricated for cartilage tissue regeneration. We prepared three groups (dECM80, dECM50, dECM20) of 3D printable hydrogels with different ratios of TOCN and dECM where SA concentration remained the same. Two-step crosslinking was performed with CaCl₂ solution to achieve the highly stable 3D printed scaffolds. Finally, the fundamental physical characterizations showed that increasing the ratio of TOCN with dECM significantly improved the viscoelastic behaviour, stability, mechanical properties, and printability of the scaffolds. Based on the results, the 3D printed dECM50 scaffolds with controlled and identical pore sizes increased the whole-layer integrity and nutrient supply in each layer of the scaffold. Furthermore, evaluation of in vitro and in vivo biocompatibility of the scaffolds with rBMSCs indicated that dECM50 scaffolds provided a suitable microenvironment for cell proliferation and promoted chondrogenesis by remarkably expressing the cartilage-specific markers. This study demonstrates that 3D printed dECM50 scaffolds provide a favourable and promising microenvironment for cartilage tissue regeneration.

The impact of adipokines on vascular networks in adipose tissue

Adipose tissue (AT) is a highly active and plastic endocrine organ. It secretes numerous soluble molecules known as adipokines, which act locally to AT control the remodel and homeostasis or exert pleiotropic functions in different peripheral organs. Aberrant production or loss of certain adipokines contributes to AT dysfunction associated with metabolic disorders, including obesity. The AT plasticity is strictly related to tissue vascularization. Angiogenesis supports the AT expansion, while regression of blood vessels is associated with AT hypoxia, which in turn mediates tissue inflammation, fibrosis and metabolic dysfunction. Several adipokines can regulate endothelial cell functions and are endowed with either pro- or anti-angiogenic properties. Here we address the role of adipokines in the regulation of angiogenesis. A better understanding of the link between adipokines and angiogenesis will open the way for novel therapeutic approaches to treat obesity and metabolic diseases.

A MgFe-LDH Nanosheet-Incorporated Smart Thermo-Responsive Hydrogel with Controllable Growth Factor Releasing Capability for Bone Regeneration

Although growth factor (GF)-loaded hydrogels have been explored as promising materials in repairing bone defects, it still remains challenging to construct smart hydrogels with excellent gelation/mechanical properties as well as controllable GF releasing capability. Herein, the incorporation of bone morphogenetic protein 2 (BMP-2)-functionalized MgFe-layered double hydroxide (LDH) nanosheets into chitosan/silk fibroin (CS) hydrogels loaded with platelet-derived growth factor-BB (PDGF-BB) to construct a smart injectable thermo-responsive hydrogel (denoted as CSP-LB), which can achieve a burst release of PDGF-BB and a sustained release of BMP-2, for highly efficient bone regeneration is reported. The incorporation of MgFe-LDH in CS hydrogel not only shortens the gelation time and decreases sol-gel transition temperature, but also enhances the mechanical property of the hydrogel. Because of the sequential release of dual-GFs and sustained release of bioactive Mg²⁺ /Fe³⁺ ions, the in vitro experiments prove that the CSP-LB hydrogel exhibits excellent angiogenic and osteogenic properties compared with the CS hydrogel. In vivo experiments further prove that the CSP-LB hydrogel can significantly enhance bone regeneration with higher bone volume and mineral density than that of the CS hydrogel. This smart thermo-sensitive CSP-LB hydrogel possesses excellent gelation capability and angiogenic and osteogenic properties, thus providing a promising minimally invasive solution for bone defect treatment.

Bioresponsive Immunotherapeutic Materials

The human immune system is an interaction network of biological processes, and its dysfunction is closely associated with a wide array of diseases, such as cancer, infectious diseases, tissue damage, and autoimmune diseases. Manipulation of the immune response network in a desired and controlled fashion has been regarded as a promising strategy for maximizing immunotherapeutic efficacy and minimizing side effects. Integration of "smart" bioresponsive materials with immunoactive agents including small molecules, biomacromolecules, and cells can achieve on-demand release of agents at targeted sites to reduce overdose-related toxicity and alleviate off-target effects. This review highlights the design principles of bioresponsive immunotherapeutic materials and discusses the critical roles of controlled release of immunoactive agents from bioresponsive materials in recruiting, housing, and manipulating immune cells for evoking desired immune responses. Challenges and future directions from the perspective of clinical translation are also discussed.

Advanced Drug Delivery System for Management of Chronic Diabetes Wound Healing

The diabetic wound is excessively vulnerable to infection because the diabetic wound suggests delayed and incomplete healing techniques. Presently, wounds and ulcers related to diabetes have additionally increased the medical burden. A diabetic wound can impair mobility, lead to amputations, or even death. In recent times, advanced drug delivery systems have emerged as promising approaches for enhancing the efficacy of wound healing treatments in diabetic patients. This review aims to provide an overview of the current advancements in drug delivery systems in managing chronic diabetic wound healing. This review begins by discussing the pathophysiological features of diabetic wounds, including impaired angiogenesis, elevated reactive oxygen species, and compromised immune response. These factors contribute to delayed wound healing and increased susceptibility to infection. The importance of early intervention and effective wound management strategies is emphasized. Various types of advanced drug delivery systems are then explored, including nanoparticles, hydrogels, transferosomes, liposomes, niosomes, dendrimers, and nanosuspension with incorporated bioactive agents and biological macromolecules are also utilized for chronic diabetes wound management. These systems offer advantages such as sustained release of therapeutic agents, improved targeting and penetration, and enhanced wound closure. Additionally, the review highlights the potential of novel approaches such as antibiotics, minerals, vitamins, growth factors gene therapy, and stem cell-based therapy in diabetic wound healing. The outcome of advanced drug delivery systems holds immense potential in managing chronic diabetic wound healing. They offer innovative approaches for delivering therapeutic agents, improving wound closure, and addressing the specific pathophysiological characteristics of diabetic wounds.

Controlled Delivery of Corticosteroids Using Tunable Tough Adhesives

Hydrogel-based drug delivery systems typically aim to release drugs locally to tissue in an extended manner. Tissue adhesive alginate-polyacrylamide tough hydrogels are recently demonstrated to serve as an extended-release system for the corticosteroid triamcinolone acetonide. Here, the stimuli-responsive controlled release of triamcinolone acetonide from the alginate-polyacrylamide tough hydrogel drug delivery systems (TADDS) and evolving new approaches to combine alginate-polyacrylamide tough hydrogel with drug-loaded nano and microparticles, generating composite TADDS is described. Stimulation with ultrasound pulses or temperature changes is demonstrated to control the release of triamcinolone acetonide from the TADDS. The incorporation of laponite nanoparticles or PLGA microparticles into the tough hydrogel is shown to further enhance the versatility to control and modulate the release of triamcinolone acetonide. A first technical exploration of a TADDS shelf-life concept is performed using lyophilization, where lyophilized TADDS are physically stable and the bioactive integrity of released triamcinolone acetonide is demonstrated. Given the tunability of properties, the TADDS are a suggested technology platform for controlled drug delivery.

Computational Analysis and Optimization of Geometric Parameters for Fibrous Scaffold Design

Bioresorbable tissue scaffolds are a promising potential treatment for soft-tissue injuries, such as tendon and ligament rupture. These materials provide temporary support to the injured tissues and provide biological cues that promote healing. Previous work has shown that fiber alignment, diameter, and spacing affect cell morphology and migration, which impact healing of the target tissue. However, previous work has not fully characterized the isolated effects of fiber alignment, diameter, and spacing on cell morphology and migration, nor has it revealed the ideal combinations of diameter and spacing to promote cell migration and elongation on fibrous scaffolds. To clarify these effects, a mesoscale model was formulated to describe cell movement on a fibrous scaffold and analyze the isolated effects of fiber alignment, diameter, and spacing. After analyzing the isolated effects, an optimization was performed to find combinations of fiber diameter and spacing that maximized cell elongation and migration, which may lead to improved healing of the target tissue. This analysis may ultimately aid the design of scaffold materials to improve outcomes after tendon or ligament rupture.

Aligned nanofibrous collagen membranes from fish swim bladder as a tough and acid-resistant suture for pH-regulated stomach perforation and tendon rupture

Background

Wound closure in the complex body environment places higher requirements on suture’s mechanical and biological performance. In the scenario of frequent mechanical gastric motility and extremely low pH, single functional sutures have limitations in dealing with stomach bleeding trauma where the normal healing will get deteriorated in acid. It necessitates to advance suture, which can regulate wounds, resist acid and intelligently sense stomach pH.

Methods

Based on fish swim bladder, a double-stranded drug-loaded suture was fabricated. Its cytotoxicity, histocompatibility, mechanical properties, acid resistance and multiple functions were verified. Also, suture’s performance suturing gastric wounds and Achilles tendon was verified in an in vivo model.

Results

By investigating the swim bladder’s multi-scale structure, the aligned tough collagen fibrous membrane can resist high hydrostatic pressure. We report that the multi-functional sutures on the twisted and aligned collagen fibers have acid resistance and low tissue reaction. Working with an implantable “capsule robot”, the smart suture can inhibit gastric acid secretion, curb the prolonged stomach bleeding and monitor real-time pH changes in rabbits and pigs. The suture can promote stomach healing and is strong enough to stitch the fractured Achilles tendon.

Conclusions

As a drug-loaded absorbable suture, the suture shows excellent performance and good application prospect in clinical work.

Enhanced tendon healing by a tough hydrogel with an adhesive side and high drug-loading capacity

Hydrogels that provide mechanical support and sustainably release therapeutics have been used to treat tendon injuries. However, most hydrogels are insufficiently tough, release drugs in bursts, and require cell infiltration or suturing to integrate with surrounding tissue. Here we report that a hydrogel serving as a high-capacity drug depot and combining a dissipative tough matrix on one side and a chitosan adhesive surface on the other side supports tendon gliding and strong adhesion (larger than 1,000 J m^-2) to tendon on opposite surfaces of the hydrogel, as we show with porcine and human tendon preparations during cyclic-friction loadings. The hydrogel is biocompatible, strongly adheres to patellar, supraspinatus and Achilles tendons of live rats, boosted healing and reduced scar formation in a rat model of Achilles-tendon rupture, and sustainably released the corticosteroid triamcinolone acetonide in a rat model of patellar tendon injury, reducing inflammation, modulating chemokine secretion, recruiting tendon stem and progenitor cells, and promoting macrophage polarization to the M2 phenotype. Hydrogels with 'Janus' surfaces and sustained-drug-release functionality could be designed for a range of biomedical applications.

Biodegradable and biocompatible synthetic polymers for applications in bone and muscle tissue engineering

In medicine, tissue engineering has made significant advances. Using tissue engineering techniques, transplant treatments result in less donor site morbidity and need fewer surgeries overall. It is now possible to create cell-supporting scaffolds that degrade as new tissue grows on them, replacing them until complete body function is restored. Synthetic polymers have been a significant area of study for biodegradable scaffolds due to their ability to provide customizable biodegradable and mechanical features as well as a low immunogenic effect due to biocompatibility. The food and drug administration has given the biodegradable polymers widespread approval after they showed their reliability. In the context of tissue engineering, this paper aims to deliver an overview of the area of biodegradable and biocompatible synthetic polymers. Frequently used synthetic biodegradable polymers utilized in tissue scaffolding, scaffold specifications, polymer synthesis, degradation factors, as well as fabrication methods are discussed. In order to emphasize the many desired properties and corresponding needs for skeletal muscle and bone, particular examples of synthetic polymer scaffolds are investigated. Increased biocompatibility, functionality and clinical applications will be made possible by further studies into novel polymer and scaffold fabrication approaches.  

Advances toward transformative therapies for tendon diseases

Approved therapies for tendon diseases have not yet changed the clinical practice of symptomatic pain treatment and physiotherapy. This review article summarizes advances in the development of novel drugs, biologic products, and biomaterial therapies for tendon diseases with perspectives for translation of integrated therapies. Shifting from targeting symptom relief toward disease modification and prevention of disease progression may open new avenues for therapies. Deep evidence-based clinical, cellular, and molecular characterization of the underlying pathology of tendon diseases, as well as therapeutic delivery optimization and establishment of multidiscipline interorganizational collaboration platforms, may accelerate the discovery and translation of transformative therapies for tendon diseases.

Rapid Ultratough Topological Tissue Adhesives

Tissue adhesives capable of achieving strong and tough adhesion in permeable wet environments are useful in many biomedical applications. However, adhesion generated through covalent bond formation directly with the functional groups of tissues (i.e., COOH and NH2  groups in collagen), or using non-covalent interactions can both be limited by weak, unstable, or slow adhesion. Here, it is shown that by combining pH-responsive bridging chitosan polymer chains and a tough hydrogel dissipative matrix one can achieve unprecedented ultratough adhesion to tissues (>2000 J m-2 ) in 5-10 min without covalent bond formation. The strong non-covalent adhesion is shown to be stable under physiologically relevant conditions and strongly influenced by chitosan molecular weight, molecular weight of polymers in the matrix, and pH. The adhesion mechanism relies primarily on the topological entanglement between the chitosan chains and the permeable adherends. To further expand the applicability of the adhesives, adhesion time can be decreased by dehydrating the hydrogel matrix to facilitate rapid chitosan interpenetration and entanglement (>1000 J m-2  in ≤1 min). The unprecedented adhesive properties presented in this study open opportunities for new strategies in the development of non-covalent tissue adhesives and numerous bioapplications.

Microenvironmentally optimized 3D-printed TGFβ-functionalized scaffolds facilitate endogenous cartilage regeneration in sheep

Clinically, microfracture is the most commonly applied surgical technique for cartilage defects. However, an increasing number of studies have shown that the clinical improvement remains questionable, and the reason remains unclear. Notably, recent discoveries revealed that signals from regenerated niches play a critical role in determining mesenchymal stem cell fate specification and differentiation. We speculate that a microenvironmentally optimized scaffold that directs mesenchymal stem cell fate will be a good therapeutic strategy for cartilage repair. Therefore, we first explored the deficiency of microfractures in cartilage repair. The microfracture not only induced inflammatory cell aggregation in blood clots but also consisted of loose granulation tissue with increased levels of proteins related to fibrogenesis. We then fabricated a functional cartilage scaffold using two strong bioactive cues, transforming growth factor-β3 and decellularized cartilage extracellular matrix, to modulate the cell fate of mesenchymal stem cells. Additionally, poly(ε-caprolactone) was also coprinted with extracellular matrix-based bioinks to provide early mechanical support. The in vitro studies showed that microenvironmentally optimized scaffolds exert powerful effects on modulating the mesenchymal stem cell fate, such as promoting cell migration, proliferation and chondrogenesis. Importantly, this strategy achieved superior regeneration in sheep via scaffolds with biomechanics (restored well-organized collagen orientation) and antiapoptotic properties (cell death-related genes were also downregulated). In summary, this study provides evidence that microenvironmentally optimized scaffolds improve cartilage regeneration in situ by regulating the microenvironment and support further translation in human cartilage repair. STATEMENT OF SIGNIFICANCE: Although microfracture (MF)-based treatment for chondral defects has been commonly used, critical gaps exist in understanding the biochemistry of MF-induced repaired tissue. More importantly, the clinically unsatisfactory effects of MF treatment have prompted researchers to focus on tissue engineering scaffolds that may have sufficient therapeutic efficacy. In this manuscript, a 3D printing ink containing cartilage tissue-specific extracellular matrix (ECM), methacrylate gelatin (GelMA), and transforming growth factor-β3 (TGF-β3)-embedded polylactic-coglycolic acid (PLGA) microspheres was coprinted with poly(ε-caprolactone) (PCL) to fabricate tissue engineering scaffolds for chondral defect repair. The sustained release of TGF-β3 from scaffolds successfully directed endogenous stem/progenitor cell migration and differentiation. This microenvironmentally optimized scaffold produced improved tissue repair outcomes in the sheep animal model, explicitly guiding more organized neotissue formation and therefore recapitulating the anisotropic structure of native articular cartilage. We hypothesized that the cell-free scaffolds might improve the clinical applicability and become a new therapeutic option for chondral defect repair.

Smart biomaterials: From 3D printing to 4D bioprinting

This century is blessed with enhanced medical facilities on the grounds of the development of smart biomaterials. The rise of the four-dimensional (4D) bioprinting technology is a shining example. Using inert biomaterials as the bioinks for the three-dimensional (3D) printing process, static objects that might not be able to mimic the dynamic nature of tissues would be fabricated; by contrast, 4D bioprinting can be used for the fabrication of stimuli-responsive cell-laden structures that can evolve with time and enable engineered tissues to undergo morphological changes in a pre-planned way. For all the aptitude of 4D bioprinting technology in tissue engineering, it is imperative to select suitable stimuli-responsive biomaterials with cell-supporting functionalities and responsiveness; as a result, in this article, recent advances and challenges in smart biomaterials for 4D bioprinting are briefly discussed. An overview perspective concerning the latest developments in 4D-bioprinting is also provided.

Characterization and Cytocompatibility of Collagen-Gelatin-Elastin (CollaGee) Acellular Skin Substitute towards Human Dermal Fibroblasts: In Vitro Assessment

Full-thickness skin wounds have become a serious burden to patients, medical care, and the socio-economic environment. The development of a safe and effective acellular skin substitute that can rapidly restore intact physiological skin is required. Natural bioactive materials including collagen, gelatin, and elastin possess significant advantages over synthetic biomaterials regarding biodegradability and biocompatibility. However, low mechanical strength, a faster biodegradation rate, and thermally unstable biomaterials lead to slow-healing and a high rate of post-implantation failure. To overcome these concerns, naturally occurring genipin (GNP) flavonoids were added to improve the mechanical strength, degradation rate, and thermal properties. Therefore, this study aimed to fabricate and characterize collagen−gelatin−elastin (CollaGee) biomaterials cross-linked with GNP as an acellular skin substitute potentially used in full-thickness wound healing. CollaGee at different ratios was divided into non-cross-linked and cross-linked with 0.1% GNP (w/v). The physicochemical, mechanical, and biocompatibility properties of CollaGee were further investigated. The results demonstrated that GNP-cross-linked CollaGee has better physicochemical (>50% porosity, pore size range of 100−200 µm, swelling ratio of >1000%) and mechanical properties (resilience and cross-linking degree of >60%, modulus of >1.0 GPa) compared to non-cross-linked CollaGee groups. Furthermore, both cross-linked and non-cross-linked CollaGee demonstrated pivotal cellular compatibility with no toxicity and sustained cell viability until day 7 towards human dermal fibroblasts. These findings suggest that GNP-cross-linked CollaGee could be a promising ready-to-use product for the rapid treatment of full-thickness skin loss.

Acellular cartilage matrix biomimetic scaffold with immediate enrichment of autologous bone marrow mononuclear cells to repair articular cartilage defects

Functional repair of articular cartilage defects is always a great challenge in joint surgery clinically. Tissue engineering strategies that combine autologous cell implantation with three-dimensional scaffolds have proven effective for repairing articular cartilage tissue. However, it faces the problem of cell sources and scaffold materials. Autologous chondrocytes and bone marrow are difficult to popularize clinically due to limited donor sources and low mononuclear cell (MNC) concentrations, respectively. The density gradient centrifugation method can increase the concentration of MNCs in fresh bone marrow by nearly a hundredfold and achieve immediate enrichment. In addition, acellular cartilage matrix (ACM), with good biocompatibility and a cartilage-specific microenvironment, is considered to be an ideal candidate scaffold for cartilage regeneration. In this study, hybrid pigs were used to establish articular cartilage defect models of different sizes to determine the feasibility and maximum scope of application of ACM-based biomimetic scaffolds combined with MNCs for inducing articular cartilage regeneration. Importantly, ACM-based biomimetic scaffolds instantly enriched MNCs could improve the repair effect of articular cartilage defects in situ, which established a new model of articular cartilage regeneration that could be applied immediately and suited for large-scale clinical promotion. The current study significantly improves the repair effect of articular cartilage defects, which provides scientific evidence and detailed insights for future clinical applications of ACM-based biomimetic scaffolds combined with MNCs.

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Explore the maximum scope of repairing articular cartilage defect with ACM scaffold.

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Immediate enrichment of mononuclear cells by density gradient centrifugation.

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ACM scaffold enriched MNCs improve the repair effect of articular cartilage defect.

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Enrichment of MNCs expands the maximum scope of repairing articular cartilage defect.

Bioactive Film-Guided Soft-Hard Interface Design Technology for Multi-Tissue Integrative Regeneration

Control over soft-to-hard tissue interfaces is attracting intensive worldwide research efforts. Herein, a bioactive film-guided soft-hard interface design (SHID) for multi-tissue integrative regeneration is shown. Briefly, a soft bioactive film with good elasticity matchable to native ligament tissue, is incorporated with bone-mimic components (calcium phosphate cement, CPC) to partially endow the soft-film with hard-tissue mimicking feature. The hybrid film is elegantly compounded with a clinical artificial ligament to act as a buffer zone to bridge the soft (ligament) and hard tissues (bone). Moreover, the bioactive film-decorated ligament can be rolled into a 3D bio-instructive implant with spatial-controllable distribution of CPC bioactive motifs. CPC then promotes the recruitment and differentiation of endogenous cells in to the implant inside part, which enables a vascularized bone growth into the implant, and forms a structure mimicking the biological ligament-bone interface, thereby significantly improving osteointegration and biomechanical property. Thus, this special design provides an effective SHID-guided implant-bioactivation strategy unreached by the traditional manufacturing methods, enlightening a promising technology to develop an ideal SHID for translational use in the future.