Chitosan hydrogel/3D-printed poly(ε-caprolactone) hybrid scaffold containing synovial mesenchymal stem cells for cartilage regeneration based on tetrahedral framework nucleic acid recruitment

Decoding interactions between biofilms and DNA nanoparticles

Biofilms present a great challenge in antimicrobial therapy due to their inherent tolerance to conventional antibiotics, promoting the need for advanced drug delivery strategies that improve therapy. While various nanoparticles (NPs) have been reported for this purpose, DNA-based NPs remain a largely unexploited resource against biofilm-associated infections. To fill this gap and to lay the groundwork for their potential therapeutic exploitation, we investigated the diffusion, penetration, and retention behaviors of three DNA-based nanocarriers -plain or modified-within P. aeruginosa biofilms. Watson-Crick base pairing or hydrophobic interactions mediated the formation of the plain NPs whilst electrostatic interaction enabled optimization of coated NPs via microfluidic mixing. We assessed the interactions of the nanocarriers with biofilm structures via Single Plane Illumination Microscopy - Fluorescence Correlation Spectroscopy (SPIM-FCS) and Confocal Laser Scanning Microscopy (CLSM). We demonstrate the impact of microfluidic parameters on the physicochemical properties of the modified DNA NPs and their subsequent distinct behaviors in the biofilm. Our results show that single stranded DNA micelles (ssDNA micelle) and tetrahedral DNA nanostructures (TDN) had similar diffusion and penetration profiles, whereas chitosan-coated TDN (TDN-Chit) showed reduced diffusion and increased biofilm retention. This is attributable to the relatively larger size and positive surface charge of the TDN-Chit NPs. The study shows first and foremost that DNA can be used as building block in drug delivery for antibiofilm therapeutics. Moreover, the overall behavioral findings are pivotal for the strategic selection of therapeutic agents to be encapsulated within these structures, possibly affecting the treatment efficacy. This research not only highlights the underexplored potential of DNA-based NPs in antibiofilm therapy but also advocates for further studies using different optimization strategies to refine these nanocarrier systems for targeted treatments in biofilm-related infections.

Three-Dimensional Bioprinting of Growth Differentiation Factor 5-Preconditioned Mesenchymal Stem Cell-Derived Exosomes Facilitates Articular Cartilage Endogenous Regeneration

The repair of articular cartilage defects remains a major regenerative and clinical challenge. Exosomes (Exos) derived from mesenchymal stem cells (MSCs) have good application potential in cartilage tissue engineering. Numerous studies have indicated that appropriate preconditioning methods can promote the therapeutic effect of Exos. Growth differentiation factor 5 (GDF-5) plays a critical role in chondrogenesis and regeneration. In this study, GDF-5 was used to precondition synovial mesenchymal stem cells (SMSCs) to increase the chondrogenic-promoting effect of Exos (G-Exos). In addition, we demonstrated that G-Exos rich in miR-383-3p increased the chondrogenic potential of SMSCs by activating the Kdm2a/SOX2 signaling pathway. On this basis, G-Exos were loaded into a glycyrrhizic acid/methacrylate-acylated hyaluronic acid (GA/HA/G-Exos) scaffold via digital light processing (DLP) bioprinting to maintain bioactivity and sustained release. The GA/HA/G-Exos scaffolds not only presented significant biological properties in vitro but also significantly promoted the remodeling of the joint cavity regenerative microenvironment and the regeneration of articular cartilage in Sprague-Dawley rats. This study provides a promising cell-free regenerative strategy for cartilage defect repair via the use of engineered exofunctionalized biological scaffolds.

A 3D-printed grid-like hyaluronic acid based hydrogel loaded with deferoxamine as wound dressing promotes diabetic wound healing

The rigid inflammatory microenvironment and impaired vascular regeneration capability are two core barriers for diabetic wound healing. As hydrogels have unique 3D porous networks and hydrophilic structure, which can facilitate oxygen exchange and function as a functional delivery system for loading cells and other biomolecules, hydrogels have clinical potentials for treating diabetic wounds. Here we developed a 3D-printed grid-like hydrogel composed of hyaluronic acid-based acrylamide (HA-AM), oxidized mannan oligosaccharide (OMOS), and deferoxamine (DFO). We demonstrated that the developed hydrogel (HA-AM/OMOS@DFO) exhibited favorable swelling, reasonable degradation time, good biocompatibility and structural support strength. Moreover, the HA-AM/OMOS@DFO hydrogel exerted antioxidative effects and inflammatory regulation functions. In addition, the loaded DFO effectively promoted vascular regeneration in the wound, which facilitated the healing of chronic diabetic wounds. Findings suggested the developed material has potential for clinical application in treating diabetic wounds.

A comprehensive review on using injectable chitosan microgels for osteochondral tissue repair

Restoring cartilage to healthy state is challenging due to low cell density and hence low regenerative capacity. The current platforms are not compatible with clinical translation and require dedicated handling of trained personnel. However, by engineering and implanting cell microaggregates in higher concentrations, efficient formation of new cartilage can be achieved, even in the absence of exogenous growth factors. Therefore, one-step surgeries are preferable for novel treatments and we need cell laden microgels allowing the formation of microaggregaets in vivo. Injectability is a key parameter for in situ forming the shape and minimally invasive clinical applications. Hydrogels as bioinks can restore damaged tissues to their primary shape. Chitosan is a polysaccharide derived from chitin with abundant usage in tissue engineering. This review highlights the use of chitosan as an injectable hydrogel for osteochondral defects. Several studies focused on encapsulating mesenchymal stem cells within chitosan hydrogels have been categorized and incorporating microfluidic devices has been identified in the forefront to form microgels. Additionally, the printability is another convenience of chitosan for using in 3D printing for cartilage tissue engineering which is described in this review.

Chitin nanocrystal-reinforced chitin/collagen composite hydrogels for annulus fibrosus repair after discectomy

Discectomy is a widely utilized approach for alleviating disc herniation; however, effective repair of postoperative annulus fibrosus (AF) defects remains a significant challenge. This study introduces a hydrogel patch with enhanced mechanical properties for AF repair fabricated using chitin (Ch), collagen (Col), and chitin nanocrystals (ChNCs) through a freeze-thaw cycling technique. The Ch and Col components constitute the matrix of the hydrogel patch, while uniformly dispersed ChNCs act as a nanofiller, markedly improving the mechanical performance (compression strain: 95 %; compression modulus: 0.27 MPa) of the resulting Ch/Col@ChNCs hydrogel patch. The patch demonstrates advantageous properties, including high porosity, superior water absorption, thermal stability, and biodegradability in simulated body fluid. In vitro assessments reveal excellent biocompatibility with AF cells and enhanced collagen deposition. Furthermore, in vivo studies confirm that the patch effectively repairs postoperative disc defects, exhibiting strong integration with surrounding tissues and facilitating the orderly regeneration of fibrous tissue. This innovative hydrogel patch, combining exceptional properties with a straightforward fabrication process, presents a viable strategy for advancing clinical biomaterials for postoperative AF repair.

3D Printing of Hydrogel Polysaccharides for Biomedical Applications: A Review

Additive manufacturing, also known as 3D printing, is becoming more and more popular because of its wide range of materials and flexibility in design. Layer by layer, 3D complex structures can be generated by the revolutionary computer-aided process known as 3D bioprinting. It is particularly crucial for youngsters and elderly patients and is a useful tool for tailored pharmaceutical therapy. A lot of research has been carried out recently on the use of polysaccharides as matrices for tissue engineering and medication delivery. Still, there is a great need to create affordable, sustainable bioink materials with high-quality mechanical, viscoelastic, and thermal properties as well as biocompatibility and biodegradability. The primary biological substances (biopolymers) chosen for the bioink formulation are proteins and polysaccharides, among the several resources utilized for the creation of such structures. These naturally occurring biomaterials give macromolecular structure and mechanical qualities (biomimicry), are generally compatible with tissues and cells (biocompatibility), and are harmonious with biological digesting processes (biodegradability). However, the primary difficulty with the cell-laden printing technique (bioprinting) is the rheological characteristics of these natural-based bioinks. Polysaccharides are widely used because they are abundant and reasonably priced natural polymers. Additionally, they serve as excipients in formulations for pharmaceuticals, nutraceuticals, and cosmetics. The remarkable benefits of biological polysaccharides-biocompatibility, biodegradability, safety, non-immunogenicity, and absence of secondary pollution-make them ideal 3D printing substrates. The purpose of this publication is to examine recent developments and challenges related to the 3D printing of stimuli-responsive polysaccharides for site-specific medication administration and tissue engineering.

Three-Dimensional Bioprinting for Intervertebral Disc Regeneration

The rising demand for organ transplants and the need for precise tissue models have positioned the in vitro biomanufacturing of tissues and organs as a pivotal area in regenerative treatment. Considerable development has been achieved in growing tissue-engineered intervertebral disc (IVD) scaffolds, designed to meet stringent mechanical and biological compatibility criteria. Among the cutting-edge approaches, 3D bioprinting stands out due to its unparalleled capacity to organize biomaterials, bioactive molecules, and living cells with high precision. Despite these advancements, polymer-based scaffolds still encounter limitations in replicating the extracellular matrix (ECM)-like environment, which is fundamental for optimal cellular activities. To overcome these challenges, integrating polymers with hydrogels has been recommended as a promising solution. This combination enables the advancement of porous scaffolds that nurture cell adhesion, proliferation, as well as differentiation. Additionally, bioinks derived from the decellularized extracellular matrix (dECM) have exhibited potential in replicating biologically relevant microenvironments, enhancing cell viability, differentiation, and motility. Hydrogels, whether derived from natural sources involving collagen and alginate or synthesized chemically, are highly valued for their ECM-like properties and superior biocompatibility. This review will explore recent advancements in techniques and technologies for IVD regeneration. Emphasis will be placed on identifying research gaps and proposing strategies to bridge them, with the goal of accelerating the translation of IVDs into clinical applications.

Bioprinted Hydrogels as Vehicles for the Application of Extracellular Vesicles in Regenerative Medicine

Three-dimensional bioprinting is a new advance in tissue engineering and regenerative medicine. Bioprinting allows manufacturing three-dimensional (3D) structures that mimic tissues or organs. The bioinks used are mainly made of natural or synthetic polymers that must be biocompatible, printable, and biodegradable. These bioinks may incorporate progenitor cells, favoring graft implantation and regeneration of injured tissues. However, the natures of biomaterials, bioprinting processes, a lack of vascularization, and immune responses are factors that limit the viability and functionality of implanted cells and the regeneration of damaged tissues. These limitations can be addressed by incorporating extracellular vesicles (EV) into bioinks. Indeed, EV from progenitor cells may have regenerative capacities, being similar to those of their source cells. Therefore, their combinations with biomaterials can be used in cell-free therapies. Likewise, they can complement the manufacture of bioinks by increasing the viability, differentiation, and regenerative ability of incorporated cells. Thus, the main objective of this review is to show how the use of 3D bioprinting technology can be used for the application of EV in regenerative medicine by incorporating these nanovesicles into hydrogels used as bioinks. To this end, the latest advances derived from in vitro and in vivo studies have been described. Together, these studies show the high therapeutic potential of this strategy in regenerative medicine.

Electrospun Polycaprolactone-Gelatin Fibrils Enabled 3D Hydrogel Microcapsules for Biomedical Applications

Microcapsules provide a microenvironment by improving the protection and delivery of cells and drugs to specific tissue areas, promoting cell integration and tissue regeneration. Effective microcapsules must not only be permeable for micronutrient diffusion but mechanically stable. Alginate hydrogel is one of the commonly used biomaterials for fabricating microcapsules due to its gel-forming ability and low toxicity. However, its mechanical instability, inertness, and excessive porosity have impeded its use. Embedding nanofibrils in the alginate hydrogel microcapsules improves their biological and mechanical properties. In this research, electrospun composite nanofibers of PCL-gelatin (PG) were first fabricated, characterized, and cryoground. The filtered and cryoground powder solution was mixed with the alginate solution and through electrospray, fabricated into microcapsules. Parameters such as flow rate, voltage, and hydrogel composition, which are critical in the electrostatic encapsulation process, were optimized. The microcapsules were further immersed in different solvent environments (DI water, complete media, and PBS), which were observed and compared for their morphology, size distribution, and mechanical stability properties. The average diameters of the PG nanofibers ranged between 0.2 and 2 μm, with an average porosity between 58 and 73%. The average size of the microcapsules varied between 300 and 900 μm, depending on the solvent environment. Overall, results showed an improved alginate 3D hydrogel network suitable for biomedical applications.

Unveiling the Potential of Tetrahedral DNA Frameworks in Clinical Medicine: Mechanisms, Advances, and Future Perspectives

As deoxyribonucleic acis (DNA) nanotechnology advances, DNA, a fundamental biological macromolecule, has been employed to treat various clinical diseases. Among the advancements in this field, tetrahedral frameworks nucleic acids (tFNAs) have gained significant attention due to their straightforward design, structural simplicity, low cost, and high yield since their introduction by Turberfield in the early 2000s. Due to its stable spatial structure, tFNAs can resist the impact of innate immune responses on DNA and nuclease activity. Meanwhile, structural programmability of tFNAs allows for the development of static tFNA-based nanomaterials through the engineering of functional oligonucleotides or therapeutic molecules and dynamic tFNAs through the attachment of stimuli-responsive DNA apparatuses. This review first summarizes the key merits of tFNAs, including natural biocompatibility, biodegradability, structural stability, unparalleled programmability, functional diversity, and efficient cellular internalization. Based on these strengths, this review comprehensively analyzes applications of tFNAs in different clinical settings, including orthopedics, stomatology, urinary system diseases, liver-related diseases, tumors, infection, neural system diseases, ophthalmic diseases, and immunoprophylaxis. We also discuss the limitations of tFNAs and the challenges encountered in preclinical studies. This review provides new perspectives for future research and valuable guidance for researchers working in this field.

Recent advances in 3D bioprinted polysaccharide hydrogels for biomedical applications: A comprehensive review

Polysaccharide hydrogels, which can mimic the natural extracellular matrix and possess appealing physicochemical and biological characteristics, have emerged as significant bioinks for 3D bioprinting. They are highly promising for applications in tissue engineering and regenerative medicine because of their ability to enhance cell adhesion, proliferation, and differentiation in a manner akin to the natural cellular environment. This review comprehensively examines the fabrication methods, characteristics, and applications of polysaccharide hydrogel-driven 3D bioprinting, underscoring its potential in tissue engineering, drug delivery, and regenerative medicine. To contribute pertinent knowledge for future research in this field, this review critically examines key aspects, including the chemistry of carbohydrates, manufacturing techniques, formulation of bioinks, and characterization of polysaccharide-based hydrogels. Furthermore, this review explores the primary advancements and applications of 3D-printed polysaccharide hydrogels, encompassing drug delivery systems with controlled release kinetics and targeted therapy, along with tissue-engineered constructs for bone, cartilage, skin, and vascular regeneration. The use of these 3D bioprinted hydrogels in innovative research fields, including disease modeling and drug screening, is also addressed. Despite notable progress, challenges, including modulating the chemistry and properties of polysaccharides, enhancing bioink printability and mechanical properties, and achieving long-term in vivo stability, have been highlighted.

Forty Years of the Use of Cells for Cartilage Regeneration: The Research Side

Background: The treatment of articular cartilage damage has always represented a problem of considerable practical interest for orthopedics. Over the years, many surgical techniques have been proposed to induce the growth of repairing tissue and limit degeneration. In 1994, the turning point occurred: implanted autologous cells paved the way for a new treatment option based more on regeneration than repair. Objectives: This review aims to outline biological and clinical advances, from the use of mature adult chondrocytes to cell-derived products, going through progenitor cells derived from bone marrow or adipose tissue and their concentrates for articular cartilage repair. Moreover, it highlights the relevance of gene therapy as a valuable tool for successfully implementing current regenerative treatments, and overcoming the limitations of the local delivery of growth factors. Conclusions: Finally, this review concludes with an outlook on the importance of understanding the role and mechanisms of action of the different cell compounds with a view to implementing personalized treatments.

Medical applications and prospects of polylactic acid materials

Polylactic acid (PLA) is a biodegradable and bio-based polymer that has gained significant attention as an environmentally friendly alternative to traditional petroleum-based plastics. In clinical treatment, biocompatible and non-toxic PLA materials enhance safety and reduce tissue reactions, while the biodegradability allows it to breakdown over time naturally, avoiding a second surgery. With the emergence of nanotechnology and three-dimensional (3D) printing, medical utilized-PLA has been produced with more structural and biological properties at both micro and macro scales for clinical therapy. This review summarizes current applications of the PLA-based biomaterials in drug delivery systems, orthopedic treatment, tissue regenerative engineering, and surgery and medical devices, providing viewpoints regarding the prospective medical utilization.

Engineering gene-activated bioprinted scaffolds for enhancing articular cartilage repair

Untreated articular cartilage injuries often result in severe chronic pain and dyskinesia. Current repair strategies have limitations in effectively promoting articular cartilage repair, underscoring the need for innovative therapeutic approaches. A gene-activated matrix (GAM) is a promising and comprehensive therapeutic strategy that integrates tissue-engineered scaffold-guided gene therapy to promote long-term articular cartilage repair by enhancing gene retention, reducing gene loss, and regulating gene release. However, for effective articular cartilage repair, the GAM scaffold must mimic the complex gradient structure of natural articular cartilage. Three-dimensional (3D) bioprinting technology has emerged as a compelling solution, offering the ability to precisely create complex microstructures that mimic the natural articular cartilage. In this review, we summarize the recent research progress on GAM and 3D bioprinted scaffolds in articular cartilage tissue engineering (CTE), while also exploring future challenges and development directions. This review aims to provide new ideas and concepts for the development of gene-activated bioprinted scaffolds with specific properties tailored to meet the stringent requirements of articular cartilage repair.

Programmable biomaterials for bone regeneration

Programmable biomaterials are distinguished by their ability to adjust properties and functions on demand, in a periodic, reversible, or sequential manner. This contrasts with traditional biomaterials, which undergo irreversible, uncontrolled changes. This review synthesizes key advances in programmable biomaterials, examining their design principles, functionalities and applications in bone regeneration. It charts the transition from traditional to programmable biomaterials, emphasizing their enhanced precision, safety and control, which are critical from clinical and biosafety standpoints. We then classify programmable biomaterials into six types: dynamic nucleic acid-based biomaterials, electrically responsive biomaterials, bioactive scaffolds with programmable properties, nanomaterials for targeted bone regeneration, surface-engineered implants for sequential regeneration and stimuli-responsive release materials. Each category is analyzed for its structural properties and its impact on bone tissue engineering. Finally, the review further concludes by highlighting the challenges faced by programmable biomaterials and suggests integrating artificial intelligence and precision medicine to enhance their application in bone regeneration and other biomedical fields.

3D-printed constructs deliver bioactive cargos to expedite cartilage regeneration

Cartilage is solid connective tissue that recovers slowly from injury, and pain and dysfunction from cartilage damage affect many people. The treatment of cartilage injury is clinically challenging and there is no optimal solution, which is a hot research topic at present. With the rapid development of 3D printing technology in recent years, 3D bioprinting can better mimic the complex microstructure of cartilage tissue and thus enabling the anatomy and functional regeneration of damaged cartilage. This article reviews the methods of 3D printing used to mimic cartilage structures, the selection of cells and biological factors, and the development of bioinks and advances in scaffold structures, with an emphasis on how 3D printing structure provides bioactive cargos in each stage to enhance the effect. Finally, clinical applications and future development of simulated cartilage printing are introduced, which are expected to provide new insights into this field and guide other researchers who are engaged in cartilage repair.

3D Printing-Based Hydrogel Dressings for Wound Healing

Skin wounds have become an important issue that affects human health and burdens global medical care. Hydrogel materials similar to the natural extracellular matrix (ECM) are one of the best candidates for ideal wound dressings and the most feasible choices for printing inks. Distinct from hydrogels made by traditional technologies, which lack bionic and mechanical properties, 3D printing can promptly and accurately create hydrogels with complex bioactive structures and the potential to promote tissue regeneration and wound healing. Herein, a comprehensive review of multi-functional 3D printing-based hydrogel dressings for wound healing is presented. The review first summarizes the 3D printing techniques for wound hydrogel dressings, including photo-curing, extrusion, inkjet, and laser-assisted 3D printing. Then, the properties and design approaches of a series of bioinks composed of natural, synthetic, and composite polymers for 3D printing wound hydrogel dressings are described. Thereafter, the application of multi-functional 3D printing-based hydrogel dressings in a variety of wound environments is discussed in depth, including hemostasis, anti-inflammation, antibacterial, skin appendage regeneration, intelligent monitoring, and machine learning-assisted therapy. Finally, the challenges and prospects of 3D printing-based hydrogel dressings for wound healing are presented.

Progress in chitin/chitosan and their derivatives for biomedical applications: Where we stand

Chitin and its deacetylated form, chitosan, have demonstrated remarkable versatility in the realm of biomaterials. Their exceptional biocompatibility, antibacterial properties, pro- and anticoagulant characteristics, robust antioxidant capacity, and anti-inflammatory potential make them highly sought-after in various applications. This review delves into the mechanisms underlying chitin/chitosan's biological activity and provides a comprehensive overview of their derivatives in fields such as tissue engineering, hemostasis, wound healing, drug delivery, and hemoperfusion. However, despite the wealth of studies on chitin/chitosan, there exists a notable trend of homogeneity in research, which could hinder the comprehensive development of these biomaterials. This review, taking a clinician's perspective, identifies current research gaps and medical challenges yet to be addressed, aiming to pave the way for a more sustainable future in chitin/chitosan research and application.

Injectable and self-healing sulfated hyaluronic acid/gelatin hydrogel as dual drug delivery system for circumferential tracheal repair

Stem cell-based therapies show promise for clinically addressing circumferential tracheal defects (CTD) through tissue engineering. However, creating a tissue-engineered tracheal tube possesses a healthy cartilage matrix and intact tube structure remains a challenge. A solution lies in the use of an injectable hydrogel with shape adaptability and chondrogenic capacity, serving as a practical and dependable platform for tubular tracheal cartilage regeneration. In this study, we developed an injectable hydrogel using modified natural polymers-hydrazide-grafted gelatin (Gelatin-ADH) and aldehyde-modified hyaluronic acid with sulfated groups (HA-CHO-SO3) via Schiff Base interaction. Additionally, aldehyde-modified β-cyclodextrin (β-CD-CHO) was introduced into the network during hydrogel formation. The negative sulfated groups and hydrophobic cavities of β-cyclodextrin facilitated the efficient encapsulation and sustained release of transforming growth factor-β1 (TGF-β1) and kartogenin (KGN) within our hydrogel. This synergistically promoted the chondrogenesis of loaded bone marrow stem cells (BMSCs). Subsequently, we employed this TGF-β1, KGN, and BMSCs loaded hydrogel to form a cartilage ring. This ring was then assembled into an engineered tracheal cartilage tube using our previously reported ring-to-tube strategy. Our results demonstrated that the engineered tracheal cartilage tube effectively repaired CTD in a rabbit model. Hence, this study introduces a novel hydrogel with significant clinical application potential for tracheal tissue engineering.

Collagen-based 3D printed poly (glycerol sebacate) composite scaffold with biomimicking mechanical properties for enhanced cartilage defect repair

Cartilage defect repair with optimal efficiency remains a significant challenge due to the limited self-repair capability of native tissues. The development of bioactive scaffolds with biomimicking mechanical properties and degradation rates matched with cartilage regeneration while simultaneously driving chondrogenesis, plays a crucial role in enhancing cartilage defect repair. To this end, a novel composite scaffold with hierarchical porosity was manufactured by incorporating a pro-chondrogenic collagen type I/II-hyaluronic acid (CI/II-HyA) matrix to a 3D-printed poly(glycerol sebacate) (PGS) framework. Based on the mechanical enforcement of PGS framework, the composite scaffold exhibited a compressive modulus of 167.0 kPa, similar to that of native cartilage, as well as excellent fatigue resistance, similar to that of native joint tissue. In vitro degradation tests demonstrated that the composite scaffold maintained structural, mass, and mechanical stability during the initial cartilage regeneration period of 4 weeks, while degraded linearly over time. In vitro biological tests with rat-derived mesenchymal stem cell (MSC) revealed that, the composite scaffold displayed increased cell loading efficiency and improved overall cell viability due to the incorporation of CI/II-HyA matrix. Additionally, it also sustained an effective and high-quality MSC chondrogenesis and abundant de-novo cartilage-like matrix deposition up to day 28. Overall, the biomimetic composite scaffold with sufficient mechanical support, matched degradation rate with cartilage regeneration, and effective chondrogenesis stimulation shows great potential to be an ideal candidate for enhancing cartilage defect repair.

A novel mesenchymal stem cell-targeting dual-miRNA delivery system based on aptamer-functionalized tetrahedral framework nucleic acids: Application to endogenous regeneration of articular cartilage

Articular cartilage injury (ACI) remains one of the key challenges in regenerative medicine, as current treatment strategies do not result in ideal regeneration of hyaline-like cartilage. Enhancing endogenous repair via microRNAs (miRNAs) shows promise as a regenerative therapy. miRNA-140 and miRNA-455 are two key and promising candidates for regulating the chondrogenic differentiation of mesenchymal stem cells (MSCs). In this study, we innovatively synthesized a multifunctional tetrahedral framework in which a nucleic acid (tFNA)-based targeting miRNA codelivery system, named A-T-M, was used. With tFNAs as vehicles, miR-140 and miR-455 were connected to and modified on tFNAs, while Apt19S (a DNA aptamer targeting MSCs) was directly integrated into the nanocomplex. The relevant results showed that A-T-M efficiently delivered miR-140 and miR-455 into MSCs and subsequently regulated MSC chondrogenic differentiation through corresponding mechanisms. Interestingly, a synergistic effect between miR-140 and miR-455 was revealed. Furthermore, A-T-M successfully enhanced the endogenous repair capacity of articular cartilage in vivo and effectively inhibited hypertrophic chondrocyte formation. A-T-M provides a new perspective and strategy for the regeneration of articular cartilage, showing strong clinical application value in the future treatment of ACI.

The Hippo signalling pathway in bone homeostasis: Under the regulation of mechanics and aging

The Hippo signalling pathway is a conserved kinase cascade that orchestrates diverse cellular processes, such as proliferation, apoptosis, lineage commitment and stemness. With the onset of society ages, research on skeletal aging-mechanics-bone homeostasis has exploded. In recent years, aging and mechanical force in the skeletal system have gained groundbreaking research progress. Under the regulation of mechanics and aging, the Hippo signalling pathway has a crucial role in the development and homeostasis of bone. We synthesize the current knowledge on the role of the Hippo signalling pathway, particularly its downstream effectors yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ), in bone homeostasis. We discuss the regulation of the lineage specification and function of different skeletal cell types by the Hippo signalling pathway. The interactions of the Hippo signalling pathway with other pathways, such as Wnt, transforming growth factor beta and nuclear factor kappa-B, are also mentioned because of their importance for modulating bone homeostasis. Furthermore, YAP/TAZ have been extensively studied as mechanotransducers. Due to space limitations, we focus on reviewing how mechanical forces and aging influence cell fate, communications and homeostasis through a dysregulated Hippo signalling pathway.

Functional Scaffolds for Bone Tissue Regeneration: A Comprehensive Review of Materials, Methods, and Future Directions

Bone tissue regeneration is a rapidly evolving field aimed at the development of biocompatible materials and devices, such as scaffolds, to treat diseased and damaged osseous tissue. Functional scaffolds maintain structural integrity and provide mechanical support at the defect site during the healing process, while simultaneously enabling or improving regeneration through amplified cellular cues between the scaffold and native tissues. Ample research on functionalization has been conducted to improve scaffold-host tissue interaction, including fabrication techniques, biomaterial selection, scaffold surface modifications, integration of bioactive molecular additives, and post-processing modifications. Each of these methods plays a crucial role in enabling scaffolds to not only support but actively participate in the healing and regeneration process in bone and joint surgery. This review provides a state-of-the-art, comprehensive overview of the functionalization of scaffold-based strategies used in tissue engineering, specifically for bone regeneration. Critical issues and obstacles are highlighted, applications and advances are described, and future directions are identified.

Aptamer-Modified Tetrahedral Framework Nucleic Acid Synergized with TGF-β3 to Promote Cartilage Protection in Osteoarthritis by Enhancing Chondrogenic Differentiation of MSCs

Characterized by progressive and irreversible degeneration of the articular cartilage (AC), osteoarthritis (OA) is the most common chronic joint disease, and there is no cure for OA at present. Recent studies suggest that enhancing the recruitment of endogenous mesenchymal stem cells (MSCs) to damaged cartilage is a promising therapeutic strategy for cartilage repair. Tetrahedral framework nucleic acid (tFNA) is a novel DNA nanomaterial and has shown great potential in the field of biomedical science. Transforming growth factor-beta 3 (TGF-β3), a vital member of the highly conserved TGF-β superfamily, is considered to induce chondrogenesis. A 66-base DNA aptamer named HM69 is reported to identify and recruit MSCs. In this study, aptamer HM69-modified tFNAs were successfully self-assembled and used to load TGF-β3 when the disulfide bonds combined. We confirmed the successful synthesis of the final composition, HM69-tFNA@TGF-β3 (HTT), by PAGE, dynamic light scattering, and atomic force microscopy. The results of in vitro experiments showed that HTT effectively induced MSC proliferation, migration, and chondrogenic differentiation. In addition, HTT-treated MSCs were shown to protect the OA chondrocytes. In DMM mice, the injection of HTT improved the therapeutic outcome of mouse pain symptoms and AC degeneration. In conclusion, this study innovatively used the disulfide bonds combined with TGF-β3 and tFNA, and an additional sequence HM69 was loaded on tFNA for the better-targeted recruitment of MSCs. HTT demonstrated its role in promoting the chondrogenesis of MSCs and cartilage protection, indicating that it might be promising for OA therapy.

Research Progress in Hydrogels for Cartilage Organoids

The repair and regeneration of cartilage has always been a hot topic in medical research. Cartilage organoids (CORGs) are special cartilage tissue created using tissue engineering techniques outside the body. These engineered organoids tissues provide models that simulate the complex biological functions of cartilage, opening new possibilities for cartilage regenerative medicine and treatment strategies. However, it is crucial to establish suitable matrix scaffolds for the cultivation of CORGs. In recent years, utilizing hydrogel to culture stem cells and induce their differentiation into chondrocytes has emerged as a promising method for the in vitro construction of CORGs. In this review, the methods for establishing CORGs are summarized and an overview of the advantages and limitations of using matrigel in the cultivation of such organoids is provided. Furthermore, the importance of cartilage tissue ECM and alternative hydrogel substitutes for Matrigel, such as alginate, peptides, silk fibroin, and DNA derivatives is discussed, and the pros and cons of using these hydrogels for the cultivation of CORGs are outlined. Finally, the challenges and future directions in hydrogel research for CORGs are discussed. It is hoped that this article provides valuable references for the design and development of hydrogels for CORGs.

Composite Hydrogel Containing Collagen-Modified Polylactic Acid-Hydroxylactic Acid Copolymer Microspheres Loaded with Tetramethylpyrazine Promotes Articular Cartilage Repair

Articular cartilage defects pose a significant challenge due to the limited self-healing ability of cartilage. However, traditional techniques face limitations including autologous chondrocyte expansion issues. This study aims to investigate the effects of the polylactic acid-glycolic acid (PLGA) and collagen-surface modified polylactic acid-glycolic acid (CPLGA) microspheres loaded with tetramethylpyrazine (TMP) on two cell types and the regeneration potential of articular cartilage. CPLGA microspheres are prepared by Steglich reaction and characterized. They evaluated the effect of TMP-loaded microspheres on HUVECs (Human Umbilical Vein Endothelial Cells) and examined the compatibility of blank microspheres with BMSCs (Bone marrow mesenchymal stromal cells) and their potential to promote cartilage differentiation. Subcutaneous implant immune tests and cartilage defect treatment are conducted to assess biocompatibility and cartilage repair potential. The results highlight the efficacy of CPLGA microspheres in promoting tissue regeneration, attributed to improved hydrophilicity and collagen-induced mitigation of degradation. Under hypoxic conditions, both CPLGA and PLGA TMP-loaded microspheres exhibit inhibitory effects on HUVEC proliferation, migration, and angiogenesis. Notably, CPLGA microspheres show enhanced compatibility with BMSCs, facilitating chondrogenic differentiation. Moreover, the CPLGA microsphere-composite hydrogel exhibits potential for cartilage repair by modulating angiogenesis and promoting BMSC differentiation.

Nanostructured Biopolymer-Based Constructs for Cartilage Regeneration: Fabrication Techniques and Perspectives

The essential functions of cartilage, such as shock absorption and resilience, are hindered by its limited regenerative capacity. Although current therapies alleviate symptoms, novel strategies for cartilage regeneration are desperately needed. Recent developments in three-dimensional (3D) constructs aim to address this challenge by mimicking the intrinsic characteristics of native cartilage using biocompatible materials, with a significant emphasis on both functionality and stability. Through fabrication methods such as 3D printing and electrospinning, researchers are making progress in cartilage regeneration; nevertheless, it is still very difficult to translate these advances into clinical practice. The review emphasizes the importance of integrating various fabrication techniques to create stable 3D constructs. Meticulous design and material selection are required to achieve seamless cartilage integration and durability. The review outlines the need to address these challenges and focuses on the latest developments in the production of hybrid 3D constructs based on biodegradable and biocompatible polymers. Furthermore, the review acknowledges the limitations of current research and provides perspectives on potential avenues for effectively regenerating cartilage defects in the future.

Strontium/Silicon/Calcium-Releasing Hierarchically Structured 3D-Printed Scaffolds Accelerate Osteochondral Defect Repair

Articular cartilage defects are a global challenge, causing substantial disability. Repairing large defects is problematic, often exceeding cartilage's self-healing capacity and damaging bone structures. To tackle this problem, a scaffold-mediated therapeutic ion delivery system is developed. These scaffolds are constructed from poly(ε-caprolactone) and strontium (Sr)-doped bioactive nanoglasses (SrBGn), creating a unique hierarchical structure featuring macropores from 3D printing, micropores, and nanotopologies due to SrBGn integration. The SrBGn-embedded scaffolds (SrBGn-µCh) release Sr, silicon (Si), and calcium (Ca) ions, which improve chondrocyte activation, adhesion, proliferation, and maturation-related gene expression. This multiple ion delivery significantly affects metabolic activity and maturation of chondrocytes. Importantly, Sr ions may play a role in chondrocyte regulation through the Notch signaling pathway. Notably, the scaffold's structure and topological cues expedite the recruitment, adhesion, spreading, and proliferation of chondrocytes and bone marrow-derived mesenchymal stem cells. Si and Ca ions accelerate osteogenic differentiation and blood vessel formation, while Sr ions enhance the polarization of M2 macrophages. The findings show that SrBGn-µCh scaffolds accelerate osteochondral defect repair by delivering multiple ions and providing structural/topological cues, ultimately supporting host cell functions and defect healing. This scaffold holds great promise for osteochondral repair applications.

In Vitro Biocompatibility Assessment of Bioengineered PLA-Hydrogel Core-Shell Scaffolds with Mesenchymal Stromal Cells for Bone Regeneration

Human mesenchymal stromal cells (hMSCs), whether used alone or together with three-dimensional scaffolds, are the best-studied postnatal stem cells in regenerative medicine. In this study, innovative composite scaffolds consisting of a core-shell architecture were seeded with bone-marrow-derived hMSCs (BM-hMSCs) and tested for their biocompatibility and remarkable capacity to promote and support bone regeneration and mineralization. The scaffolds were prepared by grafting three different amounts of gelatin-chitosan (CH) hydrogel into a 3D-printed polylactic acid (PLA) core (PLA-CH), and the mechanical and degradation properties were analyzed. The BM-hMSCs were cultured in the scaffolds with the presence of growth medium (GM) or osteogenic medium (OM) with differentiation stimuli in combination with fetal bovine serum (FBS) or human platelet lysate (hPL). The primary objective was to determine the viability, proliferation, morphology, and spreading capacity of BM-hMSCs within the scaffolds, thereby confirming their biocompatibility. Secondly, the BM-hMSCs were shown to differentiate into osteoblasts and to facilitate scaffold mineralization. This was evinced by a positive Von Kossa result, the modulation of differentiation markers (osteocalcin and osteopontin), an expression of a marker of extracellular matrix remodeling (bone morphogenetic protein-2), and collagen I. The results of the energy-dispersive X-ray analysis (EDS) clearly demonstrate the presence of calcium and phosphorus in the samples that were incubated in OM, in the presence of FBS and hPL, but not in GM. The chemical distribution maps of calcium and phosphorus indicate that these elements are co-localized in the same areas of the sections, demonstrating the formation of hydroxyapatite. In conclusion, our findings show that the combination of BM-hMSCs and PLA-CH, regardless of the amount of hydrogel content, in the presence of differentiation stimuli, can provide a construct with enhanced osteogenicity for clinically relevant bone regeneration.

Engineering Wet-Resistant and Osteogenic Nanocomposite Adhesive to Control Bleeding and Infection after Median Sternotomy

Median sternotomy surgery stands as one of the prevailing strategies in cardiac surgery. In this study, the cutting-edge bone adhesive is designed, inspired by the impressive adhesive properties found in mussels and sandcastle worms. This work has created an osteogenic nanocomposite coacervate adhesive by integrating a cellulose-polyphosphodopamide interpenetrating network, quaternized chitosan, and zinc, gallium-doped hydroxyapatite nanoparticles. This adhesive is characterized by robust catechol-metal coordination which effectively adheres to both hard and soft tissues with a maximum adhesive strength of 900 ± 38 kPa on the sheep sternum bone, surpassing that of commercial bone adhesives. The release of zinc and gallium cations from nanocomposite adhesives and quaternized chitosan matrix imparts remarkable antibacterial properties and promotes rapid blood coagulation, in vitro and ex vivo. It is also proved that this nanocomposite adhesive exhibits significant in vitro bioactivity, stable degradability, biocompatibility, and osteogenic ability. Furthermore, the capacity of nanocomposite coacervate to adhere to bone tissue and support osteogenesis contributes to the successful healing of a sternum bone defect in a rabbit model in vivo. In summary, these nanocomposite coacervate adhesives with promising characteristics are expected to provide solutions to clinical issues faced during median sternotomy surgery.

Bioprinted biomimetic hydrogel matrices guiding stem cell aggregates for enhanced chondrogenesis and cartilage regeneration

Articular cartilage tissue has limited self-repair capabilities, with damage frequently progressing to irreversible degeneration. Engineered tissues constructed through bioprinting and embedded with stem cell aggregates offer promising therapeutic alternatives. Aggregates of bone marrow mesenchymal stromal cells (BMSCs) demonstrate enhanced and more rapid chondrogenic differentiation than isolated cells, thus facilitating cartilage repair. However, it remains a key challenge to precisely control biochemical microenvironments to regulate cellular adhesion and cohesion within bioprinted matrices simultaneously. Herein, this work reports a bioprintable hydrogel matrix with high cellular adhesion and aggregation properties for cartilage repair. The hydrogel comprises an enhanced cell-adhesive gelatin methacrylate and a cell-cohesive chitosan methacrylate (CHMA), both of which are subjected to photo-initiated crosslinking. By precisely adjusting the CHMA content, the mechanical stability and biochemical cues of the hydrogels are finely tuned to promote cellular aggregation, chondrogenic differentiation and cartilage repair implantation. Multi-layer constructs encapsulated with BMSCs, with high cell viability reaching 91.1%, are bioprinted and photo-crosslinked to support chondrogenic differentiation for 21 days. BMSCs rapidly form aggregates and display efficient chondrogenic differentiation both on the hydrogels and within bioprinted constructs, as evidenced by the upregulated expression of Sox9, Aggrecan and Collagen 2a1 genes, along with high protein levels. Transplantation of these BMSC-laden bioprinted hydrogels into cartilaginous defects demonstrates effective hyaline cartilage repair. Overall, this cell-responsive hydrogel scaffold holds immense promise for applications in cartilage tissue engineering.

Enhancing chondrogenic differentiation of mesenchymal stem cells through synergistic effects of cellulose nanocrystals and plastic compression in collagen-based hydrogel for cartilage formation

Collagen-based (COL) hydrogels could be a promising treatment option for injuries to the articular cartilage (AC) becuase of their similarity to AC native extra extracellular matrix. However, the high hydration of COL hydrogels poses challenges for AC's mechanical properties. To address this, we developed a hydrogel platform that incorporating cellulose nanocrystals (CNCs) within COL and followed by plastic compression (PC) procedure to expel the excessive fluid out. This approach significantly improved the mechanical properties of the hydrogels and enhanced the chondrogenic differentiation of mesenchymal stem cells (MSCs). Radially confined PC resulted in higher collagen fibrillar densities together with reducing fibril-fibril distances. Compressed hydrogels containing CNCs exhibited the highest compressive modulus and toughness. MSCs encapsulated in these hydrogels were initially affected by PC, but their viability improved after 7 days. Furthermore, the morphology of the cells and their secretion of glycosaminoglycans (GAGs) were positively influenced by the compressed COL-CNC hydrogel. Our findings shed light on the combined effects of PC and CNCs in improving the physical and mechanical properties of COL and their role in promoting chondrogenesis.

Micro/nanoengineered agricultural by-products for biomedical and environmental applications

Agriculturally derived by-products generated during the growth cycles of living organisms as secondary products have attracted increasing interest due to their wide range of biomedical and environmental applications. These by-products are considered promising candidates because of their unique characteristics including chemical stability, profound biocompatibility and offering a green approach by producing the least impact on the environment. Recently, micro/nanoengineering based techniques play a significant role in upgrading their utility, by controlling their structural integrity and promoting their functions at a micro and nano scale. Specifically, they can be used for biomedical applications such as tissue regeneration, drug delivery, disease diagnosis, as well as environmental applications such as filtration, bioenergy production, and the detection of environmental pollutants. This review highlights the diverse role of micro/nano-engineering techniques when applied on agricultural by-products with intriguing properties and upscaling their wide range of applications across the biomedical and environmental fields. Finally, we outline the future prospects and remarkable potential that these agricultural by-products hold in establishing a new era in the realms of biomedical science and environmental research.

3D Printing of Polysaccharide-Based Hydrogel Scaffolds for Tissue Engineering Applications: A Review

In tissue engineering, 3D printing represents a versatile technology employing inks to construct three-dimensional living structures, mimicking natural biological systems. This technology efficiently translates digital blueprints into highly reproducible 3D objects. Recent advances have expanded 3D printing applications, allowing for the fabrication of diverse anatomical components, including engineered functional tissues and organs. The development of printable inks, which incorporate macromolecules, enzymes, cells, and growth factors, is advancing with the aim of restoring damaged tissues and organs. Polysaccharides, recognized for their intrinsic resemblance to components of the extracellular matrix have garnered significant attention in the field of tissue engineering. This review explores diverse 3D printing techniques, outlining distinctive features that should characterize scaffolds used as ideal matrices in tissue engineering. A detailed investigation into the properties and roles of polysaccharides in tissue engineering is highlighted. The review also culminates in a profound exploration of 3D polysaccharide-based hydrogel applications, focusing on recent breakthroughs in regenerating different tissues such as skin, bone, cartilage, heart, nerve, vasculature, and skeletal muscle. It further addresses challenges and prospective directions in 3D printing hydrogels based on polysaccharides, paving the way for innovative research to fabricate functional tissues, enhancing patient care, and improving quality of life.

Effect of tetrahedral framework nucleic acids on the reconstruction of tendon-to-bone injuries after rotator cuff tears

Clinicians and researchers have always faced challenges in performing surgery for rotator cuff tears (RCT) due to the intricate nature of the tendon-bone gradient and the limited long-term effectiveness. At the same time, the occurrence of an inflammatory microenvironment further aggravates tissue damage, which has a negative impact on the regeneration process of mesenchymal stem cells (MSCs) and eventually leads to the production of scar tissue. Tetrahedral framework nucleic acids (tFNAs), novel nanomaterials, have shown great potential in biomedicine due to their strong biocompatibility, excellent cellular internalisation ability, and unparalleled programmability. The objective of this research was to examine if tFNAs have a positive effect on regeneration after RCTs. Experiments conducted in a controlled environment demonstrated that tFNAs hindered the assembly of inflammasomes in macrophages, resulting in a decrease in the release of inflammatory factors. Next, tFNAs were shown to exert a protective effect on the osteogenic and chondrogenic differentiation of bone marrow MSCs under inflammatory conditions. The in vitro results also demonstrated the regulatory effect of tFNAs on tendon-related protein expression levels in tenocytes after inflammatory stimulation. Finally, intra-articular injection of tFNAs into a rat RCT model showed that tFNAs improved tendon-to-bone healing, suggesting that tFNAs may be promising tendon-to-bone protective agents for the treatment of RCTs.

Mesenchymal stem cells for cartilage regeneration: Insights into molecular mechanism and therapeutic strategies

The use of mesenchymal stem cells (MSCs) in cartilage regeneration has gained significant attention in regenerative medicine. This paper reviews the molecular mechanisms underlying MSC-based cartilage regeneration and explores various therapeutic strategies to enhance the efficacy of MSCs in this context. MSCs exhibit multipotent capabilities and can differentiate into various cell lineages under specific microenvironmental cues. Chondrogenic differentiation, a complex process involving signaling pathways, transcription factors, and growth factors, plays a pivotal role in the successful regeneration of cartilage tissue. The chondrogenic differentiation of MSCs is tightly regulated by growth factors and signaling pathways such as TGF-β, BMP, Wnt/β-catenin, RhoA/ROCK, NOTCH, and IHH (Indian hedgehog). Understanding the intricate balance between these pathways is crucial for directing lineage-specific differentiation and preventing undesirable chondrocyte hypertrophy. Additionally, paracrine effects of MSCs, mediated by the secretion of bioactive factors, contribute significantly to immunomodulation, recruitment of endogenous stem cells, and maintenance of chondrocyte phenotype. Pre-treatment strategies utilized to potentiate MSCs, such as hypoxic conditions, low-intensity ultrasound, kartogenin treatment, and gene editing, are also discussed for their potential to enhance MSC survival, differentiation, and paracrine effects. In conclusion, this paper provides a comprehensive overview of the molecular mechanisms involved in MSC-based cartilage regeneration and outlines promising therapeutic strategies. The insights presented contribute to the ongoing efforts in optimizing MSC-based therapies for effective cartilage repair.

Towards Complex Tissues Replication: Multilayer Scaffold Integrating Biomimetic Nanohydroxyapatite/Chitosan Composites

This study explores an approach to design and prepare a multilayer scaffold mimicking interstratified natural tissue. This multilayer construct, composed of chitosan matrices with graded nanohydroxyapatite concentrations, was achieved through an in situ biomineralization process applied to individual layers. Three distinct precursor concentrations were considered, resulting in 10, 20, and 30 wt% nanohydroxyapatite content in each layer. The resulting chitosan/nanohydroxyapatite (Cs/n-HAp) scaffolds, created via freeze-drying, exhibited nanohydroxyapatite nucleation, homogeneous distribution, improved mechanical properties, and good cytocompatibility. The cytocompatibility analysis revealed that the Cs/n-HAp layers presented cell proliferation similar to the control in pure Cs for the samples with 10% n-HAp, indicating good cytocompatibility at this concentration, while no induction of apoptotic death pathways was demonstrated up to a 20 wt% n-Hap concentration. Successful multilayer assembly of Cs and Cs/n-HAp layers highlighted that the proposed approach represents a promising strategy for mimicking multifaceted tissues, such as osteochondral ones.

Fabrication of gelatin-polyester based biocomposite scaffold via one-step functionalization of melt electrowritten polymer blends in aqueous phase

The rapid manufacturing of biocomposite scaffold made of saturated-Poly(ε-caprolactone) (PCL) and unsaturated Polyester (PE) blends with gelatin and modified gelatin (NCO-Gel) is demonstrated. Polyester blend-based scaffold are fabricated with and without applying potential in the melt electrowriting system. Notably, the applied potential induces phase separation between PCL and PE and drives the formation of PE rich spots at the interface of electrowritten fibers. The objective of the current study is to control the phase separation between saturated and unsaturated polyesters occurring in the melt electro-writing process and utilization of this phenomenon to improve efficiency of biofunctionalization at the interface of scaffold via Aza-Michael addition reaction. Electron-deficient triple bonds of PE spots on the fibers exhibit good potential for the biofunctionalization via the aza-Michael addition reaction. PE spots are found to be pronounced in which blend compositions are PCL-PE as 90:10 and 75:25 %. The biofunctionalization of scaffold is monitored through CN bond formation appeared at 400 eV via X-ray photoelectron spectroscopy (XPS) and XPS chemical mapping. The described biofunctionalization methodology suggest avoiding use of multi-step chemical modification on additive manufacturing products and thereby rapid prototyping of functional polymer blend based scaffolds with enhanced biocompatibility and preserved mechanical properties. Additionally one-step additive manufacturing method eliminates side effects of toxic solvents and long modification steps during scaffold fabrication.

Injectable hydrogels as promising in situ therapeutic platform for cartilage tissue engineering

Injectable hydrogels are gaining prominence as a biocompatible, minimally invasive, and adaptable platform for cartilage tissue engineering. Commencing with their synthesis, this review accentuates the tailored matrix formulations and cross-linking techniques essential for fostering three-dimensional cell culture and melding with complex tissue structures. Subsequently, it spotlights the hydrogels' enhanced properties, highlighting their augmented functionalities and broadened scope in cartilage tissue repair applications. Furthermore, future perspectives are advocated, urging continuous innovation and exploration to surmount existing challenges and harness the full clinical potential of hydrogels in regenerative medicine. Such advancements are crucial for validating the long-term efficacy and safety of hydrogels, positioning them as a promising direction in regenerative medicine to address cartilage-related ailments.

Molecular co-assembled strategy tuning protein conformation for cartilage regeneration

The assembly of oligopeptide and polypeptide molecules can reconstruct various ordered advanced structures through intermolecular interactions to achieve protein-like biofunction. Here, we develop a "molecular velcro"-inspired peptide and gelatin co-assembly strategy, in which amphiphilic supramolecular tripeptides are attached to the molecular chain of gelatin methacryloyl via intra-/intermolecular interactions. We perform molecular docking and dynamics simulations to demonstrate the feasibility of this strategy and reveal the advanced structural transition of the co-assembled hydrogel, which brings more ordered β-sheet content and 10-fold or more compressive strength improvement. We conduct transcriptome analysis to reveal the role of co-assembled hydrogel in promoting cell proliferation and chondrogenic differentiation. Subcutaneous implantation evaluation confirms considerably reduced inflammatory responses and immunogenicity in comparison with type I collagen. We demonstrate that bone mesenchymal stem cells-laden co-assembled hydrogel can be stably fixed in rabbit knee joint defects by photocuring, which significantly facilitates hyaline cartilage regeneration after three months. This co-assembly strategy provides an approach for developing cartilage regenerative biomaterials.

Articular cartilage repair biomaterials: strategies and applications

Articular cartilage injury is a frequent worldwide disease, while effective treatment is urgently needed. Due to lack of blood vessels and nerves, the ability of cartilage to self-repair is limited. Despite the availability of various clinical treatments, unfavorable prognoses and complications remain prevalent. However, the advent of tissue engineering and regenerative medicine has generated considerable interests in using biomaterials for articular cartilage repair. Nevertheless, there remains a notable scarcity of comprehensive reviews that provide an in-depth exploration of the various strategies and applications. Herein, we present an overview of the primary biomaterials and bioactive substances from the tissue engineering perspective to repair articular cartilage. The strategies include regeneration, substitution, and immunization. We comprehensively delineate the influence of mechanically supportive scaffolds on cellular behavior, shedding light on emerging scaffold technologies, including stimuli-responsive smart scaffolds, 3D-printed scaffolds, and cartilage bionic scaffolds. Biologically active substances, including bioactive factors, stem cells, extracellular vesicles (EVs), and cartilage organoids, are elucidated for their roles in regulating the activity of chondrocytes. Furthermore, the composite bioactive scaffolds produced industrially to put into clinical use, are also explicitly presented. This review offers innovative solutions for treating articular cartilage ailments and emphasizes the potential of biomaterials for articular cartilage repair in clinical translation.

Cartilage tissue healing and regeneration based on biocompatible materials: a systematic review and bibliometric analysis from 1993 to 2022

Cartilage, a type of connective tissue, plays a crucial role in supporting and cushioning the body, and damages or diseases affecting cartilage may result in pain and impaired joint function. In this regard, biocompatible materials are used in cartilage tissue healing and regeneration as scaffolds for new tissue growth, barriers to prevent infection and reduce inflammation, and deliver drugs or growth factors to the injury site. In this article, we perform a comprehensive bibliometric analysis of literature on cartilage tissue healing and regeneration based on biocompatible materials, including an overview of current research, identifying the most influential articles and authors, discussing prevailing topics and trends in this field, and summarizing future research directions.

Nature‐Inspired Strategies for the Treatment of Osteoarthritis

Articular cartilage is devoid of nerves and blood vessels, and its nutrients must be obtained from the joint fluid; therefore, its ability to repair itself is limited. Manufactured materials such as artificial cartilage or synthetic materials are typically used in traditional approaches for knee cartilage repair. However, durability, postimplant rejection, and tissue incompatibility are the problems associated with these materials. In recent decades, tissue engineering and regenerative medicine have focused on the development of functional substitutes, particularly those based on naturally inspired biopolymers. This review focuses on sustainably produced biopolymers based on materials derived from natural sources. Furthermore, these materials have many advantages, including low antigenicity, biocompatibility, and degradability. Of course, there are also many challenges associated with natural materials, such as the lack of clinical studies and long‐term follow‐up data, unstable mechanical properties of the materials, and high demands placed on preparation and molding techniques. In this review, an overview of natural and nature‐inspired polymers that are the subject of research to date, as well as their structural designs and product performances is provided. This review provides scientific guidance for enhancing the development of naturally inspired materials for treating cartilage injuries.

Raising the Bar: Progress in 3D-Printed Hybrid Bone Scaffolds for Clinical Applications: A Review

Damage to bones resulting from trauma and tumors poses a significant challenge to human health. Consequently, current research in bone damage healing centers on developing three-dimensional (3D) scaffolding materials that facilitate and enhance the regeneration of fractured bone tissues. In this context, the careful selection of materials and preparation processes is essential for creating demanding scaffolds for bone tissue engineering. This is done to optimize the regeneration of fractured bones. This study comprehensively analyses the latest scientific advancements and difficulties in developing scaffolds for bone tissue creation. Initially, we clarified the composition and process by which bone tissue repairs itself. The review summarizes the primary uses of materials, both inorganic and organic, in scaffolds for bone tissue engineering. In addition, we present a comprehensive study of the most recent advancements in the mainstream techniques used to prepare scaffolds for bone tissue engineering. We also examine the distinct advantages of each method in great detail. This article thoroughly examines potential paths and obstacles in bone tissue engineering scaffolds for clinical applications.

Recent advances of exosomes in soft tissue injuries in sports medicine: A critical review on biological and biomaterial applications

Sports medicine is generally associated with soft tissue injuries including muscle injuries, meniscus and ligament injuries, tendon ruptures, tendinopathy, rotator cuff tears, and tendon-bone healing during injuries. Tendon and ligament injuries are the most common sport injuries accounting for 30-40% of all injuries. Therapies for tendon injuries can be divided into surgical and non-surgical methods. Surgical methods mainly depend on the operative procedures, the surgeons and postoperative interventions. In non-surgical methods, cell therapy with stem cells and cell-free therapy with secretome of stem cell origin are current directions. Exosomes are the main paracrine factors of mesenchymal stem cells (MSCs) containing biological components such as proteins, nucleic acids and lipids. Compared with MSCs, MSC-exosomes (MSC-exos) possess the capacity to escape phagocytosis and achieve long-term circulation. In addition, the functions of exosomes from various cell sources in soft tissue injuries in sports medicine have been gradually revealed in recent years. Along with the biological and biomaterial advances in exosomes, exosomes can be designed as drug carriers with biomaterials and exosome research is providing promising contributions in cell biology. Exosomes with biomaterial have the potential of becoming one of the novel therapeutic modalities in regenerative researches. This review summarizes the derives of exosomes in soft tissue regeneration and focuses on the biological and biomaterial mechanism and advances in exosomal therapy in soft tissue injuries.

Recent advances in 3D bioprinted cartilage-mimicking constructs for applications in tissue engineering

Human cartilage tissue can be categorized into three types: hyaline cartilage, elastic cartilage and fibrocartilage. Each type of cartilage tissue possesses unique properties and functions, which presents a significant challenge for the regeneration and repair of damaged tissue. Bionics is a discipline in which humans study and imitate nature. A bionic strategy based on comprehensive knowledge of the anatomy and histology of human cartilage is expected to contribute to fundamental study of core elements of tissue repair. Moreover, as a novel tissue-engineered technology, 3D bioprinting has the distinctive advantage of the rapid and precise construction of targeted models. Thus, by selecting suitable materials, cells and cytokines, and by leveraging advanced printing technology and bionic concepts, it becomes possible to simultaneously realize multiple beneficial properties and achieve improved tissue repair. This article provides an overview of key elements involved in the combination of 3D bioprinting and bionic strategies, with a particular focus on recent advances in mimicking different types of cartilage tissue.

A Membrane-Targeted Photosensitizer Prevents Drug Resistance and Induces Immune Response in Treating Candidiasis

Candida albicans (C. albicans), a ubiquitous polymorphic fungus in humans, causes different types of candidiasis, including oral candidiasis (OC) and vulvovaginal candidiasis (VVC), which are physically and mentally concerning and financially costly. Thus, developing alternative antifungals that prevent drug resistance and induce immunity to eliminate Candida biofilms is crucial. Herein, a novel membrane-targeted aggregation-induced emission (AIE) photosensitizer (PS), TBTCP-QY, is developed for highly efficient photodynamic therapy (PDT) of candidiasis. TBTCP-QY has a high molar absorption coefficient and an excellent ability to generate 1 O2 and •OH, entering the interior of biofilms due to its high permeability. Furthermore, TBTCP-QY can efficiently inhibit biofilm formation by suppressing the expression of genes related to the adhesion (ALS3, EAP1, and HWP1), invasion (SAP1 and SAP2), and drug resistance (MDR1) of C. albicans, which is also advantageous for eliminating potential fungal resistance to treat clinical infectious diseases. TBTCP-QY-mediated PDT efficiently targets OC and VVC in vivo in a mouse model, induces immune response, relieves inflammation, and accelerates the healing of mucosal defects to combat infections caused by clinically isolated fluconazole-resistant strains. Moreover, TBTCP-QY demonstrates excellent biocompatibility, suggesting its potential applications in the clinical treatment of OC and VVC.

Emerging advances in hydrogel-based therapeutic strategies for tissue regeneration

Significant developments in cell therapy and biomaterial science have broadened the therapeutic landscape of tissue regeneration. Tissue damage is a complex biological process in which different types of cells play a specific role in repairing damaged tissues and growth factors strictly regulate the activity of these cells. Hydrogels have become promising biomaterials for tissue regeneration if appropriate materials are selected and the hydrogel properties are well-regulated. Importantly, they can be used as carriers for living cells and growth factors due to the high water-holding capacity, high permeability, and good biocompatibility of hydrogels. Cell-loaded hydrogels can play an essential role in treating damaged tissues and open new avenues for cell therapy. There is ample evidence substantiating the ability of hydrogels to facilitate the delivery of cells (stem cell, macrophage, chondrocyte, and osteoblast) and growth factors (bone morphogenetic protein, transforming growth factor, vascular endothelial growth factor and fibroblast growth factor). This paper reviewed the latest advances in hydrogels loaded with cells or growth factors to promote the reconstruction of tissues. Furthermore, we discussed the shortcomings of the application of hydrogels in tissue engineering to promote their further development.

3D-printed PCL scaffolds with anatomy-inspired bionic stratified structures for the treatment of growth plate injuries

The growth plate is a cartilaginous tissue with three distinct zones. Resident chondrocytes are highly organized in a columnar structure, which is critical for the longitudinal growth of immature long bones. Once injured, the growth plate may potentially be replaced by bony bar formation and, consequently, cause limb abnormalities in children. It is well-known that the essential step in growth plate repair is the remolding of the organized structure of chondrocytes. To achieve this, we prepared an anatomy-inspired bionic Poly(ε-caprolactone) (PCL) scaffold with a stratified structure using three-dimensional (3D) printing technology. The bionic scaffold is engineered by surface modification of NaOH and collagen Ⅰ (COL Ⅰ) to promote cell adhesion. Moreover, chondrocytes and bone marrow mesenchymal stem cells (BMSCs) are loaded in the most suitable ratio of 1:3 for growth plate reconstruction. Based on the anatomical structure of the growth plate, the bionic scaffold is designed to have three regions, which are the small-, medium-, and large-pore-size regions. These pore sizes are used to induce BMSCs to differentiate into similar structures such as the growth plate. Remarkably, the X-ray and histological results also demonstrate that the cell-loaded stratified scaffold can successfully rebuild the structure of the growth plate and reduce limb abnormalities, including limb length discrepancies and angular deformities in vivo. This study provides a potential method of preparing a bioinspired stratified scaffold for the treatment of growth plate injuries.