Tissue Engineering Research Articles

The Edifice of Vasculature-On-Chips: A Focused Review on the Key Elements and Assembly of Angiogenesis Models.

The conception of vascularized organ-on-a-chip models provides researchers with the ability to supply controlled biological and physical cues that simulate the in vivo dynamic microphysiological environment of native blood vessels. The intention of this niche research area is to improve our understanding of the role of the vasculature in health or disease progression in vitro by allowing researchers to monitor angiogenic responses and cell-cell or cell-matrix interactions in real time. This review offers a comprehensive overview of the essential elements, including cells, biomaterials, microenvironmental factors, microfluidic chip design, and standard validation procedures that currently govern angiogenesis-on-a-chip assemblies. In addition, we emphasize the importance of incorporating a microvasculature component into organ-on-chip devices in critical biomedical research areas, such as tissue engineering, drug discovery, and disease modeling. Ultimately, advances in this area of research could provide innovative solutions and a personalized approach to ongoing medical challenges.

Tailoring Network Topology in Mechanically Robust Hydrogels for 3D Printing and Injection.

Tissue engineering and regenerative medicine are confronted with a persistent challenge: the urgent demand for robust, load-bearing, and biocompatible scaffolds that can effectively endure substantial deformation. Given that inadequate mechanical performance is typically rooted in structural deficiencies─specifically, the absence of energy dissipation mechanisms and network uniformity─a crucial step toward solving this problem is generating synthetic approaches that enable exquisite control over network architecture. This work systematically explores structure-property relationships in poly(ethylene glycol)-based hydrogels constructed utilizing thiol-yne chemistry. We systematically vary polymer concentration, constituent molar mass, and cross-linking protocols to understand the impact of architecture on hydrogel mechanical properties. The network architecture was resolved within the molecular model of Rubinstein-Panyukov to obtain the densities of chemical cross-links and entanglements. We employed both nucleophilic and radical pathways, uncovering notable differences in mechanical response, which highlight a remarkable degree of versatility achievable by tuning readily accessible parameters. Our approach yielded hydrogels with good cell viability and remarkably robust tensile and compression profiles. Finally, the hydrogels are shown to be amenable to advanced processing techniques by demonstrating injection- and extrusion-based 3D printing. Tuning the mechanism and network regularity during the cell-compatible formation of hydrogels is an emerging strategy to control the properties and processability of hydrogel biomaterials by making simple and rational design choices.

A Pump-Free Strategy for the Controllable Generation of Alginate Microgels as Cellular Microcarriers.

Microgels are advanced scaffolds for tissue engineering due to their proper biodegradability, good biocompatibility, and high specific surface area for effective oxygen and nutrient transfer. However, most of the current monodispersed microgel fabrication systems rely heavily on various precision pumps, which highly increase the cost and complexity of their downstream application. In this work, we developed a simple and facile system for the controllable generation of uniform alginate microgels by integrating a gas-shearing strategy into a glass microfluidic device. Importantly, the cell-laden microgels can be rapidly prepared in a pump-free manner under an all-aqueous environment. The three-dimensional cultured green fluorescent protein-human A549 cells in alginate microgels exhibited enhanced stemness and drug resistance compared to those under two-dimensional conditions. The pancreatic cancer organoids in alginate microgels exhibited some of the key features of pancreatic cancer. The proposed microgels showed decent monodispersity, biocompatibility, and versatility, providing great opportunities in various biomedical applications such as microcarrier fabricating, organoid engineering, and high-throughput drug screening.

Biomaterials-based Technologies in Skeletal Muscle Tissue Engineering.

For many clinically prevalent severe injuries, the inherent regenerative capacity of skeletal muscle remains inadequate. Skeletal muscle tissue engineering (SMTE) seeks to meet this clinical demand. With continuous progress in biomedicine and related technologies including micro/nanotechnology and 3D printing, numerous studies have uncovered various intrinsic mechanisms regulating skeletal muscle regeneration and developed tailored biomaterial systems based on these understandings. Here, we discussed the skeletal muscle structure and regeneration process and explored in detail the diverse biomaterial systems derived from various technologies. Biomaterials serve not merely as local niches for cell growth, but also as scaffolds endowed with structural or physicochemical properties that provide tissue regenerative cues such as topographical, electrical, and mechanical signals. They can also act as delivery systems for stem cells and bioactive molecules that have been shown as key participants in endogenous repair cascades. To achieve bench-to-bedside translation, we have also summarized the typical effect enabled by biomaterial systems and the potential underlying molecular mechanisms. We hope to provide insights into the roles of biomaterials in SMTE from cellular and molecular perspectives. Finally, we provided perspectives on the advancement of SMTE, for which gene therapy, exosomes, and hybrid biomaterials may hold promise to make important contributions. This article is protected by copyright. All rights reserved.

Research progress in the development of 3D skin models and their application to in vitro skin irritation testing.

Toxicological assessment of chemicals is crucial for safeguarding human health and the environment. However, traditional animal experiments are associated with ethical, technical, and predictive limitations in assessing the toxicity of chemicals to the skin. With the recent development of bioengineering and tissue engineering, three-dimensional (3D) skin models have been commonly used as an alternative for toxicological studies. The skin consists of the subcutaneous, dermis, and epidermis. All these layers have crucial functions such as physical and biological protection and thermoregulation. The epidermis is the shallowest layer protecting against external substances and media. Because the skin is the first contact point for many substances, this organ is very significant for assessing local toxicity following skin exposure. According to the classification of the United Nations Global Harmonized System, skin irritation is a major potentially hazardous characteristic of chemicals, and this characteristic must be accurately assessed and classified for enhancing chemical safety management and preventing and reducing chemical accidents. This review discusses the research progress of 3D skin models and introduces their application in assessing chemical skin irritation.

Synthesis and active manipulation of magnetic liquid beads

We report the fabrication and characterisation of magnetic liquid beads with a solid magnetic shell and liquid core using microfluidic techniques. The liquid beads consist of a fluorinated oil core and a polymer shell with magnetite particles. The beads are generated in a flow-focusing polydimethylsiloxane (PDMS) device and cured by photo polymerisation. We investigated the response of the liquid beads to an external magnetic field by characterising their motion towards a permanent magnet. Magnetic sorting of liquid beads in a channel was achieved with 90% efficiency. The results show that the liquid beads can be controlled magnetically and have potential applications in digital microfluidics including nucleic acid amplification, drug delivery, cell culture, sensing, and tissue engineering. The present paper also discusses the magnetophoretic behaviour of the liquid bead by varying its mass and magnetite concentration in the shell. We also demonstrated the two-dimensional self-assembly of magnetic liquid beads for potential use in digital polymerase chain reaction and digital loop mediated isothermal amplification.Graphical abstract

Therapeutic Precision: Unveiling the Potential of 3D Printing in Drug Delivery, Tissue Engineering, and Regenerative Medicine

Therapeutic Precision: Unveiling the Potential of 3D Printing in Drug Delivery, Tissue Engineering, and Regenerative Medicine

Angiogenic potential in periodontal stem cells from upper and lower jaw: A pilot study.

Teeth and supporting oral tissues are attractive and accessible sources of stem cells. Periodontal ligament stem cells (PDLSC) are readily isolated from extracted third molars, and exhibit the ability to self-renew and differentiate into multiple mesodermal cell fates. Clinical experience suggests that the exact location of periodontal defects affects the oral bone remodeling and wound healing. Compared to the mandible, the maxilla heals quicker and more efficiently. Angiogenesis is key in tissue regeneration including dental tissues, yet few studies focus on the angiogenic potential of PDLSC, none of which considered the differences between upper and lower jaw PDLSC (u-PDLSC and l-PDLSC, respectively). Here we studied the angiogenic potential of u-PDLSC and l-PDLSC and compared the results to well-established mesenchymal stem cells (MSC). Cells were characterized in terms of surface markers, proliferation, and vascular endothelial growth factor (VEGF) secretion, and angiogenic assays were performed. Newly formed capillaries were stained with CD31, and their expression of platelet endothelial cell adhesion molecule (PECAM-1), angiopoietin 2 (ANGPT2), and vascular endothelial growth factor receptor 1 and 2 (VEGFR-1, VEGFR-2) were measured. Periodontal stem cells from the upper jaw showed a higher proliferation capacity, secreted more VEGF, and formed capillary networks faster and denser than l-PDLSC. Gene expression of angiogenesis-related genes was significantly higher in u-PDLSC than in l-PDLSC or MSC, given that culture conditions were suitable. The oral cavity is a valuable source of stem cells, particularly PDLSC, which are promising for oral tissue engineering due to their robust growth, lifelong accessibility, low immunogenicity, and strong differentiation potential. Notably, u-PDLSC exhibit higher VEGF secretion and accelerate capillary formation compared to l-PDLSC or MSC. This study suggests a potential molecular mechanism in capillary formation, emphasizing the significance of precise location isolation of PDLSC.

Elderberry (Sambucus nigra) and hawthorn (Crataegus oxyacantha) extract additives in carboxymethyl chitosan scaffolds for osteochondral tissue engineering applications

Elderberry (<i>Sambucus nigra</i>) and hawthorn (<i>Crataegus oxyacantha</i>) extract additives in carboxymethyl chitosan scaffolds for osteochondral tissue engineering applications

Inorganic polymers as drug carriers: opportunities and challenges

Innovative methods and significant developments in designing new synthetic inorganic materials have been used to overcome limitations of current drug delivery systems. Inorganic polymers are widely used in the field of biomedicine, imaging, tissue engineering and drug delivery because of their bioactivity, biocompatibility, and stability. A few of the more well-known wholly inorganic polymers are portland cement, silicon dioxide, polyanionic glasses (including titania- and aluminosilicate glasses), poly(sulphur nitride), polycrystalline diamond, graphite, poly(sulphur nitride), and alumi¬num-silicate materials. Inorganic polymers, especially those possessing significant porosity, are good potential candi¬dates for the delivery of several drugs (anticancer, antibiotics, and anti-inflammatories), providing advantages such as encapsulation, controlled delivery, and improved targeting of drugs. Choosing a suitable drug carrier with a selec¬tive targeting potential also seems to be a very promising way for improving stability as well as selectivity. Despite all the advances, developing homogeneous inorganic polymers with narrow molecular weight distributions is a multidis¬ciplinary challenge. The current keynote speech provides a review of the opportunities and challenges of using inor¬ganic polymers as drug carriers.

Reconstructing Curves: A Bottom-Up Approach towards adipose tissue regeneration with Recombinant Biomaterials.

The potential of recombinant materials in the field of adipose tissue engineering (ATE) is investigated using a bottom-up tissue engineering (TE) approach. This study explores the synthesis of different photo-crosslinkable gelatin derivatives, including both natural and recombinant materials, with a particular emphasis on chain growth and step growth polymerization. Gelatin type B (Gel-B) and a recombinant collagen peptide (RCPhC1) are used as starting materials. The gel fraction and mass swelling properties of 2D hydrogel films are evaluated, revealing high gel fractions exceeding 94% and high mass swelling ratios > 15. In vitro experiments with encapsulated adipose-derived stem cells (ASCs) indicate viable cells (> 85%) throughout the experiment with the RCPhC1-based hydrogels showing a higher number of stretched ASCs. Triglyceride assays show the enhanced differentiation potential of RCPhC1 materials. Moreover, the secretome analysis reveal the production of adipose tissue-specific proteins including adiponectin, adipsin, lipocalin-2/NGAL and PAL-1. RCPhC1-based materials exhibit higher levels of adiponectin and adipsin production, indicating successful differentiation into the adipogenic lineage. Overall, this study highlights the potential of recombinant materials for ATE applications, providing insights into their physico-chemical properties, mechanical strength, and cellular interactions. This article is protected by copyright. All rights reserved.

Teicoplanin-Decorated Reduced Graphene Oxide Incorporated Silk Protein Hybrid Hydrogel for Accelerating Infectious Diabetic Wound Healing and Preventing Diabetic Foot Osteomyelitis.

Developing hybrid hydrogel dressings with anti-inflammatory, antioxidant, angiogenetic, and antibiofilm activities with higher bone tissue penetrability to accelerate diabetic wound healing and prevent diabetic foot osteomyelitis (DFO) is highly desirable in managing diabetic wounds. Herein, the glycopeptide teicoplanin is used for the first time as a green reductant to chemically reduce graphene oxide (GO). The resulting teicoplanin-decorated reduced graphene oxide (rGO) is incorporated into a mixture of silk proteins (SP) and crosslinked with genipin to yield a physicochemically crosslinked rGO-SP hybrid hydrogel. This hybrid hydrogel exhibits high porosity, self-healing, shear-induced thinning, increased cell proliferation and migration, and mechanical properties suitable for tissue engineering. Moreover, the hybrid hydrogel eradicates bacterial biofilms with a high penetrability index in agar and hydroxyapatite disks covered with biofilms, mimicking bone tissue. In vivo, the hybrid hydrogel accelerates the healing of noninfected wounds in a diabetic rat and infected wounds in a diabetic mouse by upregulating anti-inflammatory cytokines and downregulating matrix metalloproteinase-9, promoting M2 macrophage polarization and angiogenesis. The implantation of hybrid hydrogel into the infected site of mouse tibia improves bone regeneration. Hence, the rGO-SP hybrid hydrogel can be a promising wound dressing for treating infectious diabetic wounds, providing a further advantage in preventing DFO.

Preparation of Ag@3D-TiO2 Scaffolds and Determination of its Antimicrobial Properties and Osteogenesis-promoting Ability.

The micro-nano structure of 3D-printed porous titanium (Ti) alloy with excellent performance in avoiding stress shielding and promoting bone tissue differentiation provides a new opportunity for the development of bone implants, but it necessitates higher requirements for bone tissue differentiation and the antibacterial properties of bone implants in clinical practice. This study investigated the preparation, antimicrobial properties, and osteogenesis-promoting ability of the 3D printed porous Ti alloy anodic oxidized Ag-carrying (Ag@3D-TiO2) scaffolds. The 3D printed porous Ti alloy (3D-Ti), anodized 3D printed porous Ti alloy (3D-TiO2), and Ag@3D-TiO2 scaffolds were synthesized using electron beam melting. The antimicrobial properties of the scaffolds were examined using antibacterial tests and their cytocompatibility was assessed using a cell proliferation assay and acridine orange/ethidium bromide (AO/EB) staining. In vitro cellular assays were used to investigate the effects of the scaffold microstructural features on cell activity, proliferation, and osteogenesis-related genes and proteins. In vivo animal experiments were used to evaluate the anti-inflammatory and osteogenesis-promoting abilities of the scaffolds. The Ag@3D-TiO2 scaffolds exhibited sustained anti-microbial activity over time, enhanced cell proliferation, facilitated osteogenic differentiation, and increased extracellular matrix mineralization. In addition, alkaline phosphatase (ALP), collagen type I (COL-I), and osteocalcin (OCN)-related genes and proteins were upregulated. In vivo animal implantation experiments, the anti-inflammatory effect of the Ag@3D-TiO2 scaffolds were observed using histology, and a large amount of fibrous connective tissue was present around it; the Ag@3D-TiO2 scaffolds were more bio-compatible with the surrounding tissues compared with 3D-Ti and 3D-TiO2; a large amount of uniformly distributed neoplastic bone tissue existed in their pores, and the chronic systemic toxicity test showed that the 3D-Ti, 3D-TiO2, and Ag@3D-TiO2 scaffolds are biologically safe. The goal of this study was to create a scaffold that exhibits antimicrobial properties and can aid bone growth, making it highly suitable for use in bone tissue engineering.

Incorporation of essential oils in polymeric films for biomedical applications.

Natural and synthetic biodegradable polymers are widely used to obtain more sustainable films with biological, physicochemical, and mechanical properties for biomedical purposes. The incorporation of essential oils (EOs) in polymeric films can optimize the biological activities of these EOs, protect them from degradation, and serve as a prototype for new biotechnological products. This article aims to discuss updates over the last 10 years on incorporating EOs into natural and synthetic biodegradable polymer films for biomedical applications. Chitosan, alginates, cellulose, and proteins such as gelatine, silk, and zein are among the natural polymers most commonly used to prepare biodegradable films for release EOs. In addition to these, the most cited synthetic biodegradable polymers are poly(L-lactide) (PLA), poly(vinyl alcohol) (PVA), and poly(ε-caprolactone) (PCL). The EOs of clove, cinnamon, tea tree, eucalyptus, frankincense, lavender, thyme and oregano incorporated into polymeric films have been the most studied EOs in recent years in the biomedical field. Biomedical applications include antimicrobial activity against pathogenic bacteria and fungi, anticancer activity, potential for tissue engineering and regeneration with scaffolds and wound healing as dressings. Thus, this article reports on the importance of incorporating EOs into biodegradable polymer films, making these systems especially attractive for various biomedical applications.

CT-Visible Microspheres Enable Whole-Body In Vivo Tracking of Injectable Tissue Engineering Scaffolds.

Targeted delivery and retention are essential requirements for implantable tissue-engineered products. Non-invasive imaging methods that can confirm location, retention, and biodistribution of transplanted cells attached to implanted tissue engineering scaffolds will be invaluable for the optimization and enhancement of regenerative therapies. To address this need, an injectable tissue engineering scaffold consisting of highly porous microspheres compatible with transplantation of cells is modified to contain the computed tomography (CT) contrast agent barium sulphate (BaSO4). The trackable microspheres show high x-ray absorption, with contrast permitting whole-body tracking. The microspheres are cellularized with GFP+ Luciferase+ mesenchymal stem cells and show in vitro biocompatibility. In vivo, cellularized BaSO4-loaded microspheres are delivered into the hindlimb of mice where they remain viable for 14 days. Co-registration of 3D-bioluminescent imagingand µCT reconstructions enable the assessment of scaffold material and cell co-localization. The trackable microspheres are also compatible with minimally-invasive delivery by ultrasound-guided transthoracic intramyocardial injections in rats. These findings suggest that BaSO4-loaded microspheres can be used as a novel tool for optimizing delivery techniques and tracking persistence and distribution of implanted scaffold materials. Additionally, the microspheres can be cellularized and have the potential to be developed into an injectable tissue-engineered combination product for cardiac regeneration.

Dimensional and Structural Instability of Electrospun Polylactic Acid Membranes in Liquid Environments: Role of Water, Ethanol, and Temperature

AbstractElectrospun nanofibres of polylactic acid (PLA) are suggested for a variety of uses, including scaffolds for tissue engineering, components of drug delivery devices, sustainable packaging materials and membranes for liquid filtration/purification. For all these applications, it is critical to consider the stability of the PLA electrospun materials once in operation. Exposure to certain liquids and temperatures can modify their dimensions, shape, surface topography and mechanical response and compromise their performance. In this study, electrospun PLA mats were exposed to water and ethanol solutions, at different temperatures and for defined time periods, and changes in their properties were analysed. It was found that the impact of water on area shrinkage and fibre arrangement strongly depended on temperature, particularly if the treatment was performed at the glass transition temperature of PLA. Ethanol, instead, induced significant alterations in the size, morphology, and elastic modulus of the electrospun mats, even at room temperature and determined the formation of crimped structures. This work provides insights into the conditions that can critically affect the properties of PLA electrospun fibres and, hence, impact on their usage.

Stem Cell‐Based Therapies and Tissue Engineering Innovations for Tendinopathy: A Comprehensive Review of Current Strategies and Future Directions

AbstractTendon diseases commonly lead to physical disability, exerting a profound impact on the routine of affected patients. These conditions respond poorly to existing treatments, presenting a substantial challenge for orthopedic scientists. Research into clinical translational therapy has yet to yield highly versatile interventions capable of effectively addressing tendon diseases, including tendinopathy. Stem cell‐based therapies have emerged as a promising avenue for modifying the biological milieu through the secretion of regenerative and immunomodulatory factors. The current review provides an overview of the intricate tendon microenvironment, encompassing various tendon stem progenitor cells within distinct tendon sublocations, gene regulation, and pathways pertinent to tendon development, and the pathology of tendon diseases. Subsequently, the advantages of stem cell‐based therapies are discussed that utilize distinct types of autologous and allogeneic stem cells for tendon regeneration at the translational level. Moreover, this review outlines the challenges, gaps, and future innovations to propose a consolidated stem cell‐based therapy to treat tendinopathy. Finally, regenerative soluble therapies, insoluble bio‐active therapies, along with insoluble bio‐active therapies, and implantable 3D scaffolds for tendon tissue engineering are discussed, thereby presenting a pathway toward enhanced tissue regeneration and engineering.

Highly stretchable and customizable microneedle electrode arrays for intramuscular electromyography.

Stretchable three-dimensional (3D) penetrating microelectrode arrays have potential utility in various fields, including neuroscience, tissue engineering, and wearable bioelectronics. These 3D microelectrode arrays can penetrate and conform to dynamically deforming tissues, thereby facilitating targeted sensing and stimulation of interior regions in a minimally invasive manner. However, fabricating custom stretchable 3D microelectrode arrays presents material integration and patterning challenges. In this study, we present the design, fabrication, and applications of stretchable microneedle electrode arrays (SMNEAs) for sensing local intramuscular electromyography signals ex vivo. We use a unique hybrid fabrication scheme based on laser micromachining, microfabrication, and transfer printing to enable scalable fabrication of individually addressable SMNEA with high device stretchability (60 to 90%). The electrode geometries and recording regions, impedance, array layout, and length distribution are highly customizable. We demonstrate the use of SMNEAs as bioelectronic interfaces in recording intramuscular electromyography from various muscle groups in the buccal mass of Aplysia.

A rabbit osteochondral defect (OCD) model for evaluation of tissue engineered implants on their biosafety and efficacy in osteochondral repair

Osteochondral defect (OCD) is a common but challenging condition in orthopaedics that imposes huge socioeconomic burdens in our aging society. It is imperative to accelerate the R&amp;amp;D of regenerative scaffolds using osteochondral tissue engineering concepts. Yet, all innovative implant-based treatments require animal testing models to verify their feasibility, biosafety, and efficacy before proceeding to human trials. Rabbit models offer a more clinically relevant platform for studying OCD repair than smaller rodents, while being more cost-effective than large animal models. The core-decompression drilling technique to produce full-thickness distal medial femoral condyle defects in rabbits can mimic one of the trauma-relevant OCD models. This model is commonly used to evaluate the implant’s biosafety and efficacy of osteochondral dual-lineage regeneration. In this article, we initially indicate the methodology and describe a minimally-invasive surgical protocol in a step-wise manner to generate a standard and reproducible rabbit OCD for scaffold implantation. Besides, we provide a detailed procedure for sample collection, processing, and evaluation by a series of subsequent standardized biochemical, radiological, biomechanical, and histological assessments. In conclusion, the well-established, easy-handling, reproducible, and reliable rabbit OCD model will play a pivotal role in translational research of osteochondral tissue engineering.

Delivery of miRNAs Using Porous Silicon Nanoparticles Incorporated into 3D Hydrogels Enhances MSC Osteogenesis by Modulation of Fatty Acid Signaling and Silicon Degradation.

Strategies incorporating mesenchymal stromal cells (MSC), hydrogels and osteoinductive signals offer promise for bone repair. Osteoinductive signals such as growth factors face challenges in clinical translation due to their high cost, low stability and immunogenicity leading to interest in microRNAs as a simple, inexpensive and powerful alternative. The selection of appropriate miRNA candidates and their efficient delivery must be optimised to make this a reality. This study evaluated pro-osteogenic miRNAs and used porous silicon nanoparticles modified with polyamidoamine dendrimers (PAMAM-pSiNP) to deliver these to MSC encapsulated within gelatin-PEG hydrogels. miR-29b-3p, miR-101-3p and miR-125b-5p are strongly pro-osteogenic and are shown to target FASN and ELOVL4 in the fatty acid biosynthesis pathway to modulate MSC osteogenesis. Hydrogel delivery of miRNA:PAMAM-pSiNP complexes enhanced transfection compared to 2D. The osteogenic potential of hBMSC in hydrogels with miR125b:PAMAM-pSiNP complexes is evaluated. Importantly, a dual-effect on osteogenesis occurred, with miRNAs increasing expression of alkaline phosphatase (ALP) and Runt-related transcription factor 2 (RUNX2) whilst the pSiNPs enhanced mineralisation, likely via degradation into silicic acid. Overall, this work presents insights into the role of miRNAs and fatty acid signalling in osteogenesis, providing future targets to improve bone formation and a promising system to enhance bone tissue engineering.