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Cardiovascular disease has emerged as the leading cause of death worldwide. Since coronary arteries, carotid arteries, and other blood vessels are prone to narrowing, small‐diameter artificial blood channels offer a crucial solution for restoring blood flow. Ideal grafts must emulate the structure of natural blood vessels, possess adequate mechanical strength, ensure long‐term patency, and incorporate functional cells with minimal immunogenicity. Enhanced cell sources and engineering methods are vital for the creation of functional small‐diameter blood vessels (SDBVs). Among potential cell sources, stem cells stand out due to their ability to differentiate into multiple cell types, self‐renew, and exhibit low immunogenicity. Additionally, three‐dimensionally (3D) printed vascular stents have attracted widespread attention for their precision and controllable bioink application. The need for tissue‐engineered blood vessels is currently rising, and innovative design concepts integrating stem cells and 3D printing present promising solutions. Herein, the construction requirements of vascular grafts are reviewed, current status of using stem cells as a cell source and 3D printing as an engineering strategy is described, and prospects and challenges for the development of SDBVs in the medical field are discussed.

Ongoing obstacles in preclinical drug testing have raised significant concerns within the pharmaceutical industry. Recently, utilizing the potential of three‐dimensional (3D) bioprinting offers a solution for creating tissue models for screening of the effectiveness and safety of new drugs. In this study, the anti‐inflammatory potential of garlic extracts is assessed, specifically N‐Benzyl‐N‐methyl‐dodecan‐1‐amine (BMDA), using a 3D bioprinted artificial skin model. Comprehensive physicochemical characterization and immunocytochemical analysis demonstrate that the 3D bioprinted skin model exhibits structures and functions resembling human skin. BMDA treatment in a prepared skin model reveals its capacity to mitigate H2O2‐induced oxidative stress and trigger anti‐inflammatory responses. Notably, BMDA reduces the expression of pro‐inflammatory cytokines and chemokines by downregulating NF‐κB and mitogen‐activated protein kinase inflammatory signaling pathways. In summary, our findings highlight the potential of an artificial skin model as a robust platform for the development of new drugs.

Abstract Spinal cord injury (SCI) is a central nervous system disorder that can lead to sensory and motor dysfunction, which can seriously increase pressure and economic burden on families and societies. The current SCI treatment is mainly to stabilize the spine, prevent secondary damage, and control inflammation. Drug treatment is limited to early, large‐scale use of steroids to reduce the effects of edema after SCI. In short, there is no direct treatment for SCI. Recent 3D bioprinting development provides a new solution for SCI treatment: a series of spinal cord bionic scaffolds are being developed to improve spinal cord function after injury. This paper reviews the pathophysiological characteristics of SCI, current treatment methods, and the progress of 3D bioprinting in SCI. Finally, its challenges and prospects in SCI treatment are summarized.

Addressing the urgent need for effective fracture treatments, this study investigates the efficacy of a 3D bioprinted biomimetic hydrogel, enriched with bone marrow mesenchymal stem cells (BMSCs) and targeted hypoxia-inducible factor 1 alpha (Hif1a) gene activation, in enhancing fracture healing. A photocross-linkable bioink, gelatin methacryloyl bone matrix anhydride (GBMA) is developed, and selected its 5% concentration for bioink formulation. Rat BMSCs are isolated and combined with GBMA to create the GBMA@BMSCs bioink. This bioink is then used in 3D bioprinting to fabricate a hydrogel for application in a rat femoral fracture model. Through transcriptome sequencing, WGCNA, and Venn analysis, the hypoxia-inducible factor Hif1a is identified as a critical gene in the fracture healing process. In vitro studies showed that Hif1a promoted BMSC proliferation, chondrogenic differentiation, and cartilage matrix stability. The in vivo application of the GBMA@BMSCs hydrogel with Hif1a overexpression significantly accelerated fracture healing, evidenced by early and enhanced cartilage callus formation. The study demonstrates that 3D bioprinting of GBMA@BMSCs hydrogel, particularly with Hif1a-enhanced BMSCs, offers a promising approach for rapid and effective fracture repair., (© 2024 Wiley‐VCH GmbH.)

A regenerative peripheral nerve interface (RPNI) offers a therapeutic solution for nerve injury through reconstruction of the target muscle. However, implanting a transected peripheral nerve into an autologous skeletal muscle graft in RPNI causes donor-site morbidity, highlighting the need for tissue-engineered skeletal muscle constructs. Here, an engineered regenerative isolated peripheral nerve interface (eRIPEN) is developed using 3D skeletal cell printing combined with direct electrospinning to create a nanofiber membrane envelop for host nerve implantation. In this in vivo study, after over 8 months of RPNI surgery, the eRIPEN exhibits a minimum Feret diameter of 15-20 µm with a cross-sectional area of 100-500 µm 2 , representing the largest distribution of myofibers. Furthermore, neuromuscular junction formation and muscle contraction with a force of ≈28 N are observed. Notably, the decreased hypersensitivity to mechanical/thermal stimuli and an improved tibial functional index from -77 to -56 are found in the eRIPEN group. The present novel concept of eRIPEN paves the way for the utilization and application of tissue-engineered constructs in RPNI, ultimately realizing neuroprosthesis control through synaptic connections., (© 2024 Wiley‐VCH GmbH.)

Significant progress has been made in tissue engineering (TE), aiming at providing personalized solutions and overcoming the current limitations of traditional tissue and organ transplantation. 3D bioprinting has emerged as a transformative technology in the field, able to mimic key properties of the natural architecture of the native tissues. However, most successes in the area are still limited to avascular or thin tissues due to the difficulties in controlling the vascularization of the engineered tissues. To address this issue, several molecules, biomaterials, and cells with pro- and anti-angiogenic potential have been intensively investigated. Furthermore, different bioreactors capable to provide a dynamic environment for in vitro vascularization control have been also explored. The present review summarizes the main molecules and TE strategies used to promote and inhibit vascularization in TE, as well as the techniques used to deliver them. Additionally, it also discusses the current challenges in 3D bioprinting and in tissue maturation to control in vitro/in vivo vascularization. Currently, this field of investigation is of utmost importance and may open doors for the design and development of more precise and controlled vascularization strategies in TE., (© 2024 Wiley‐VCH GmbH.)

Suspension bath-based 3D bioprinting (SUB3BP) is effective in creating engineered vascular structures. The transfer of oxygen and nutrients via engineered vascular networks is necessary for tissue or organ survival and integration following transplantation. Existing SUB3BP techniques face challenges in fabricating hierarchical structures with multicellular organization, including issues related to suspension bath removal, restricted material choices, and low accuracy. A next-generation SUB3BP technique that is removal-free and multicellular is presented. A simple, storable, stable, and scalable starch hydrogel design leverages the diverse spectrum of hydrogels available for use in SUB3BP. Starch granules (8.1 µm) create vascular structures with minimal surface roughness (2.5 µm) that simulate more natural vessel walls compared to prior research. The development of cells and organoids, as well as the bioprinting of multicellular skin models with vasculature, demonstrates that starch suspension baths eliminate the removal process and have the potential for fabricating artificial tissue with a hierarchical structure and multicellular distribution., (© 2024 Wiley‐VCH GmbH.)

Embedded 3D bioprinting techniques have emerged as a powerful method to fabricate 3D engineered constructs using low strength bioinks; however, there are challenges in simultaneously satisfying the requirements of high-cell-activity, high-cell-proportion, and low-viscosity bioinks. In particular, the printing capacity of embedded 3D bioprinting is limited as two main challenges: spreading and diffusion, especially for liquid, high-cell-activity bioinks that can facilitate high-cell-proportion. Here, a liquid-in-liquid 3D bioprinting (LL3DBP) strategy is developed, which used a liquid granular bath to prevent the spreading of liquid bioinks during 3D printing, and electrostatic interaction between the liquid bioinks and liquid granular baths is found to effectively prevent the diffusion of liquid bioinks. As an example, the printing of positively charged 5% w/v gelatin methacryloyl (GelMA) in a liquid granular bath prepared with negatively charged κ-carrageenan is proved to be achievable. By LL3DBP, printing capacity is greatly advanced and bioinks with over 90% v/v cell can be printed, and printed structures with high-cell-proportion exhibit excellent bioactivity., (© 2024 Wiley‐VCH GmbH.)

There is an unmet need for in vitro cancer models that emulate the complexity of human tissues. 3D-printed solid tumor micromodels based on decellularized extracellular matrices (dECMs) recreate the biomolecule-rich matrix of native tissue. Herein a 3D in vitro metastatic melanoma model that is amenable for drug screening purposes and recapitulates features of both the tumor and the skin microenvironment is described. Epidermal, basement membrane, and dermal biocompatible inks are prepared by means of combined chemical, mechanical, and enzymatic processes. Bioink printability is confirmed by rheological assessment and bioprinting, and bioinks are subsequently combined with melanoma cells and dermal fibroblasts to build complex 3D melanoma models. Cells are tracked by confocal microscopy and surface-enhanced Raman spectroscopy (SERS) mapping. Printed dECMs and cell tracking allow modeling of the initial steps of metastatic disease, and may be used to better understand melanoma cell behavior and response to drugs., (© 2024 The Author(s). Advanced Healthcare Materials published by Wiley‐VCH GmbH.)

The ability to promote three-dimensional (3D) self-organization of induced pluripotent stem cells into complex tissue structures called organoids presents new opportunities for the field of developmental biology. Brain organoids have been used to investigate principles of neurodevelopment and neuropsychiatric disorders and serve as a drug screening and discovery platform. However, brain organoid cultures are currently limited by a lacking ability to precisely control their extracellular environment. Here, this work employs 3D bioprinting to generate a high-throughput, tunable, and reproducible scaffold for controlling organoid development and patterning. Additionally, this approach supports the coculture of organoids and vascular cells in a custom architecture containing interconnected endothelialized channels. Printing fidelity and mechanical assessments confirm that fabricated scaffolds closely match intended design features and exhibit stiffness values reflective of the developing human brain. Using organoid growth, viability, cytoarchitecture, proliferation, and transcriptomic benchmarks, this work finds that organoids cultured within the bioprinted scaffold long-term are healthy and have expected neuroectodermal differentiation. Lastly, this work confirms that the endothelial cells (ECs) in printed channel structures can migrate toward and infiltrate into the embedded organoids. This work demonstrates a tunable 3D culturing platform that can be used to create more complex and accurate models of human brain development and underlying diseases., (© 2024 The Author(s). Advanced Healthcare Materials published by Wiley‐VCH GmbH.)

Granular hydrogels composed of hydrogel microparticles are promising candidates for 3D bioprinting due to their ability to protect encapsulated cells. However, to achieve high print fidelity, hydrogel microparticles need to jam to exhibit shear-thinning characteristics, which is crucial for 3D printing. Unfortunately, this overpacking can significantly impact cell viability, thereby negating the primary advantage of using hydrogel microparticles to shield cells from shear forces. To overcome this challenge, a novel solution: a biphasic, granular colloidal bioink designed to optimize cell viability and printing fidelity is introduced. The biphasic ink consists of cell-laden polyethylene glycol (PEG) hydrogel microparticles embedded in a continuous gelatin methacryloyl (GelMA)-nanosilicate colloidal network. Here, it is demonstrated that this biphasic bioink offers outstanding rheological properties, print fidelity, and structural stability. Furthermore, its utility for engineering complex tissues with multiple cell types and heterogeneous microenvironments is demonstrated, by incorporating β-islet cells into the PEG microparticles and endothelial cells in the GelMA-nanosilicate colloidal network. Using this approach, it is possible to induce cell patterning, enhance vascularization, and direct cellular function. The proposed biphasic bioink holds significant potential for numerous emerging biomedical applications, including tissue engineering and disease modeling., (© 2024 The Author(s). Advanced Healthcare Materials published by Wiley‐VCH GmbH.)

The muscle-tendon junction (MTJ) plays a pivotal role in efficiently converting the muscular contraction into a controlled skeletal movement through the tendon. Given its complex biomechanical intricacy, the biofabrication of such tissue interface represents a significant challenge in the field of musculoskeletal tissue engineering. Herein, a novel method to produce MTJ-like hydrogel yarns using a microfluidics-assisted 3D rotary wet-spinning strategy is developed. Optimization of flow rates, rotational speed, and delivery time of bioinks enables the production of highly compartmentalized scaffolds that recapitulate the muscle, tendon, and the transient MTJ-like region. Additionally, such biofabrication parameters are validated in terms of cellular response by promoting an optimal uniaxial alignment for both muscle and tendon precursor cells. By sequentially wet-spinning C2C12 myoblasts and NIH 3T3 fibroblasts, a gradient-patterned cellular arrangement mirroring the intrinsic biological heterogeneity of the MTJ is successfully obtained. The immunofluorescence assessment further reveals the localized expression of tissue-specific markers, including myosin heavy chain and collagen type I/III, which demonstrate muscle and tenogenic tissue maturation, respectively. Remarkably, the muscle-tendon transition zone exhibits finger-like projection of the multinucleated myotubes in the tenogenic compartment, epitomizing the MTJ signature architecture., (© 2024 The Author(s). Advanced Healthcare Materials published by Wiley‐VCH GmbH.)

Decellularized small intestine submucosa (dSIS) is a promising biomaterial for promoting tissue regeneration. Isolated from the submucosal layer of animal jejunum, SIS is rich in extracellular matrix (ECM) proteins, including collagen, laminin, and fibronectin. Following mild decellularization, dSIS becomes an acellular matrix that supports cell adhesion, proliferation, and differentiation. Conventional dSIS matrix is usually obtained by thermal crosslinking, which yields a soft scaffold with low stability. To address these challenges, dSIS has been modified with methacrylate groups for photocrosslinking into stable hydrogels. However, dSIS has not been modified with clickable handles for orthogonal crosslinking. Here, we report the development of norbornene-modified dSIS, named dSIS-NB, via reacting amine groups of dSIS with carbic anhydride in acidic aqueous reaction conditions. Using triethylamine (TEA) as a mild base catalyst, we obtained high degrees of NB substitution on dSIS. In addition to describing the synthesis of dSIS-NB, we explored its adaptability in orthogonal hydrogel crosslinking and used dSIS-NB hydrogels for cancer and vascular tissue engineering. Impressively, compared with physically crosslinked dSIS and collagen matrices, orthogonally crosslinked dSIS-NB hydrogels supported rapid dissemination of cancer cells and superior vasculogenic and angiogenic properties. dSIS-NB was also exploited as a versatile bioink for 3D bioprinting applications., Competing Interests: Conflict of interest statement The authors have no conflicts of interest to declare.

Heart valve disease poses a significant clinical challenge, especially in pediatric populations, due to the inability of existing valve replacements to grow or respond biologically to their microenvironment. Tissue-engineered heart valves (TEHVs) provide a solution by facilitating patient-specific models for self-repair and remodeling. In this study, a 3D-bioprinted TEHV is designed to emulate the trilayer leaflet structure of an aortic valve. A cell-laden hydrogel scaffold made from gelatin methacrylate and polyethylene glycol diacrylate (GelMA/PEGDA) incorporates valvular interstitial-like (VIC-like) cells, being reinforced with a layer of polycaprolactone (PCL). The composition of the hydrogel scaffold remains stable over 7 days, having increased mechanical strength compared to pure GelMA. The scaffold maintains VIC-like cell function and promotes extracellular matrix (ECM) protein expression up to 14 days under two dynamic culture conditions: shear stress and stretching; replicating heart valve behavior within a more physiological-like setting and suggesting remodeling potential via ECM synthesis. This TEHV offers a promising avenue for valve replacements, closely replicating the structural and functional attributes of a native aortic valve, leading to mechanical and biological integration through biomaterial-cellular interactions., (© 2024 Wiley‐VCH GmbH.)

A current challenge in 3D bioprinting of skin equivalents is to recreate the distinct basal and suprabasal layers and promote their direct interactions. Such a structural arrangement is essential to establish 3D stratified epidermis disease models, such as for the autoimmune skin disease pemphigus vulgaris (PV), which targets the cell–cell junctions at the interface of the basal and suprabasal layers. Inspired by epithelial regeneration in wound healing, a method that combines 3D bioprinting and spatially guided self‐reorganization of keratinocytes is developed to recapture the fine structural hierarchy that lies in the deep layers of the epidermis. Herein, keratinocyte‐laden fibrin hydrogels are bioprinted to create geographical cues, guiding dynamic self‐reorganization of cells through collective migration, keratinocyte differentiation, and vertical expansion. This process results in a region of self‐organized multilayers (SOMs) that contain the basal‐to‐suprabasal transition, marked by the expressed levels of different types of keratins that indicate differentiation. Finally, the reconstructed skin tissue as an in vitro platform to study the pathogenic effects of PV is demonstrated, illuminating a significant difference in cell–cell junction dissociation induced by PV antibodies in different epidermis layers, which indicates their applications in the preclinical test of possible therapies.

In this study, a new-generation tissue-engineered bone capable of temporally regulating the immune response, balancing proinflammatory and anti-inflammatory activities, and facilitating bone regeneration and repair to address the challenges of delayed healing and nonunion in large-sized bone defects, is innovatively developed. Using the innovative techniques including multiphysics-assisted combined decellularization, side-chain biochemical modification, and sterile freeze-drying, a novel photocurable extracellular matrix hydrogel, methacrylated bone-derived decellularized extracellular matrix (bdECM-MA), is synthesized. After incorporating the bdECM-MA with silicon-substituted calcium phosphate and bone marrow mesenchymal stem cells, the tissue-engineered bone is fabricated through digital light processing 3D bioprinting. This study provides in vitro confirmation that the engineered bone maintains high cellular viability while achieving MPa-level mechanical strength. Moreover, this engineered bone exhibits excellent osteogenesis, angiogenesis, and immunomodulatory functions. One of the molecular mechanisms of the immunomodulatory function involves the inhibition of the p38-MAPK pathway. A pioneering in vivo discovery is that the natural biomaterial-based tissue-engineered bone demonstrates sequential immunomodulatory properties that activate proinflammatory and anti-inflammatory responses in succession, significantly accelerating the repair of bone defects. This study provides a new research basis and an effective method for developing autogenous bone substitute materials and treating large-sized bone defects., (© 2024 Wiley‐VCH GmbH.)

Three-dimensional (3D) bioprinting using photocrosslinkable hydrogels has gained considerable attention due to its versatility in various applications, including tissue engineering and drug delivery. Egg White (EW) is an organic biomaterial with excellent potential in tissue engineering. It provides abundant proteins, along with biocompatibility, bioactivity, adjustable mechanical properties, and intrinsic antiviral and antibacterial features. Here, we have developed a photocrosslinkable hydrogel derived from EW through methacryloyl modification, resulting in Egg White methacryloyl (EWMA). Upon exposure to UV light, synthesized EWMA becomes crosslinked, creating hydrogels with remarkable bioactivity. These hydrogels offer adjustable mechanical and physical properties compatible with most current bioprinters. The EWMA hydrogels closely resemble the native extracellular matrix (ECM) due to cell-binding and matrix metalloproteinase-responsive motifs inherent in EW. In addition, EWMA promotes cell growth and proliferation in 3D cultures. It facilitates vascularization when investigated with human umbilical vein endothelial cells (HUVECs), making it an attractive replacement for engineering hemocompatible vascular grafts and biomedical implants. In summary, the EWMA matrix enables the biofabrication of various living constructs. This breakthrough enhances the development of physiologically relevant 3D in vitro models and opens many opportunities in regenerative medicine.

3D bioprinting allows rapid automated fabrication and can be applied for high throughput generation of biomimetic constructs for in vitro drug screening. Decellularized extracellular matrix (dECM) hydrogel is a popular biomaterial choice for tissue engineering and studying carcinogenesis as a tumor microenvironmental mimetic. This study proposes a method for high throughput bioprinting with decellularized adipose tissue (DAT) based hydrogels for 3D breast cancer modeling. A comparative analysis of decellularization protocol using detergent-based and detergent-free decellularization methods for caprine-origin adipose tissue is performed, and the efficacy of dECM hydrogel for 3D cancer modeling is assessed. Histological, biochemical, morphological, and biological characterization and analysis showcase the cytocompatibility of DAT hydrogel. The rheological property of DAT hydrogel and printing process optimization is assessed to select a bioprinting window to attain 3D breast cancer models. The bioprinted tissues are characterized for cellular viability and tumor cell-matrix interactions. Additionally, an approach for breast cancer modeling is shown by performing rapid high throughput bioprinting in a 96-well plate format, and in vitro drug screening using 5-fluorouracil is performed on 3D bioprinted microtumors. The results of this study suggest that high throughput bioprinting of cancer models can potentially have downstream clinical applications like multi-drug screening platforms and personalized disease models., (© 2024 Wiley‐VCH GmbH.)

The growing aging population, with its associated chronic diseases, underscores the urgency for effective tissue regeneration strategies. Biomaterials play a pivotal role in the realm of tissue reconstruction and regeneration, with a distinct shift toward minimally invasive (MI) treatments. This transition, fueled by engineered biomaterials, steers away from invasive surgical procedures to embrace approaches offering reduced trauma, accelerated recovery, and cost-effectiveness. In the realm of MI tissue repair and cargo delivery, various techniques are explored. While in situ polymerization is prominent, it is not without its challenges. This narrative review explores diverse biomaterials, fabrication methods, and biofunctionalization for injectable pre-formed scaffolds, focusing on their unique advantages. The injectable pre-formed scaffolds, exhibiting compressibility, controlled injection, and maintained mechanical integrity, emerge as promising alternative solutions to in situ polymerization challenges. The conclusion of this review emphasizes the importance of interdisciplinary design facilitated by synergizing fields of materials science, advanced 3D biomanufacturing, mechanobiological studies, and innovative approaches for effective MI tissue regeneration., (© 2024 Wiley‐VCH GmbH.)

Pluripotent stem cell-derived skin organoids (PSOs) emerge as a developmental skin model that is self-organized into multiple components, such as hair follicles. Despite their impressive complexity, PSOs are currently generated in the absence of 3D extracellular matrix (ECM) signals and have several major limitations, including an inverted anatomy (e.g., epidermis inside/dermis outside). In this work, a method is established to generate PSOs effectively in a chemically-defined 3D ECM environment. After examining various dermal ECM molecules, it is found that PSOs generated in collagen -type I (COLI) supplemented with laminin 511 (LAM511) exhibit increased growth compared to conventional free-floating conditions, but fail to induce complete skin differentiation due in part to necrosis. This problem is addressed by generating the PSOs in a 3D bioprinted spindle-shaped hydrogel device, which constrains organoid growth longitudinally. This culture system significantly reduces organoid necrosis and leads to a twofold increase in keratinocyte differentiation and an eightfold increase in hair follicle formation. Finally, the system is adapted as a microfluidic device to create asymmetrical gradients of differentiation factors and improves the spatial organization of dermal and epidermal cells. This study highlights the pivotal role of ECM and morphogen gradients in promoting and spatially-controlling skin differentiation in the PSO framework., (© 2024 Wiley‐VCH GmbH.)

3-D bioprinting is a promising technology to fabricate custom geometries for tissue engineering. However, most bioprintable hydrogels are weak and fragile, difficult to handle and cannot mimetic the mechanical behaviors of the native soft elastic tissues. We have developed a visible light crosslinked, single-network, elastic and biocompatible hydrogel system based on an acrylated triblock copolymer of poly(ethylene glycol) PEG and polycaprolactone (PCL) (PEG-PCL-DA). To enable its application in bioprinting of soft tissues, we have modified the hydrogel system on its printability and biodegradability. Furthermore, we hypothesize that this elastic material can better transmit pulsatile forces to cells, leading to enhanced cellular response under mechanical stimulation. This central hypothesis was tested using vascular conduits with smooth muscle cells (SMCs) cultured under pulsatile forces in a custom-made bioreactor. The results showed that vascular conduits made of PEG-PCL-DA hydrogel faithfully recapitulate the rapid stretch and recoil under the pulsatile pressure from 1 to 3 Hz frequency, which induced a contractile SMC phenotype, consistently upregulated the core contractile transcription factors. In summary, our work demonstrates the potential of elastic hydrogel for 3D bioprinting of soft tissues by fine tuning the printability, biodegradability, while possess robust elastic property suitable for manual handling and biomechanical stimulation.

Addressing large bone defects remains a significant challenge owing to the inherent limitations in self-healing capabilities, resulting in prolonged recovery and suboptimal regeneration. Although current clinical solutions are available, they have notable shortcomings, necessitating more efficacious approaches to bone regeneration. Organoids derived from stem cells show great potential in this field; however, the development of bone organoids has been hindered by specific demands, including the need for robust mechanical support provided by scaffolds and hybrid extracellular matrices (ECM). In this context, bioprinting technologies have emerged as powerful means of replicating the complex architecture of bone tissue. The research focused on the fabrication of a highly intricate bone ECM analog using a novel bioink composed of gelatin methacrylate/alginate methacrylate/hydroxyapatite (GelMA/AlgMA/HAP). Bioprinted scaffolds facilitate the long-term cultivation and progressive maturation of extensive bioprinted bone organoids, foster multicellular differentiation, and offer valuable insights into the initial stages of bone formation. The intrinsic self-mineralizing quality of the bioink closely emulates the properties of natural bone, empowering organoids with enhanced bone repair for both in vitro and in vivo applications. This trailblazing investigation propels the field of bone tissue engineering and holds significant promise for its translation into practical applications., (© 2024 Wiley‐VCH GmbH.)

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, the skeletal muscle structure and regeneration process are discussed and the diverse biomaterial systems derived from various technologies are explored in detail. 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, the typical effect enabled by biomaterial systems and the potential underlying molecular mechanisms are also summarized. Insights into the roles of biomaterials in SMTE from cellular and molecular perspectives are provided. Finally, perspectives on the advancement of SMTE are provided, for which gene therapy, exosomes, and hybrid biomaterials may hold promise to make important contributions., (© 2024 Wiley‐VCH GmbH.)

3D bioprinting of elastic cartilage tissues that are mechanically and structurally comparable to their native counterparts, while exhibiting favorable cellular behavior, is an unmet challenge. A practical solution for this problem is the multi-material bioprinting of thermoplastic polymers and cell-laden hydrogels using multiple nozzles. However, the processing of thermoplastic polymers requires high temperatures, which can damage hydrogel-encapsulated cells. In this study, the authors developed waterborne polyurethane (WPU)-polycaprolactone (PCL) composites to allow multi-material co-printing with cell-laden gelatin methacryloyl (GelMA) hydrogels. These composites can be extruded at low temperatures (50-60 °C) and high speeds, thereby reducing heat/shear damage to the printed hydrogel-capsulated cells. Furthermore, their hydrophilic nature improved the cell behavior in vitro. More importantly, the bioprinted structures exhibited good stiffness and viscoelasticity compared to native elastic cartilage. In summary, this study demonstrated low-temperature multi-material bioprinting of WPU-PCL-based constructs with good mechanical properties, degradation time-frames, and cell viability, showcasing their potential in elastic cartilage bio-fabrication and regeneration to serve broad biomedical applications in the future., (© 2024 Wiley‐VCH GmbH.)

Vascular cell overgrowth and lumen size reduction in pulmonary vein stenosis (PVS) can result in elevated PV pressure, pulmonary hypertension, cardiac failure, and death. Administration of chemotherapies such as rapamycin have shown promise by inhibiting the vascular cell proliferation; yet clinical success is limited due to complications such as restenosis and off-target effects. The lack of in vitro models to recapitulate the complex pathophysiology of PVS has hindered the identification of disease mechanisms and therapies. This study integrated 3D bioprinting, functional nanoparticles, and perfusion bioreactors to develop a novel in vitro model of PVS. Bioprinted bifurcated PV constructs are seeded with endothelial cells (ECs) and perfused, demonstrating the formation of a uniform and viable endothelium. Computational modeling identified the bifurcation point at high risk of EC overgrowth. Application of an external magnetic field enabled targeting of the rapamycin-loaded superparamagnetic iron oxide nanoparticles at the bifurcation site, leading to a significant reduction in EC proliferation with no adverse side effects. These results establish a 3D bioprinted in vitro model to study PV homeostasis and diseases, offering the potential for increased throughput, tunability, and patient specificity, to test new or more effective therapies for PVS and other vascular diseases., (© 2024 The Authors. Advanced Science published by Wiley‐VCH GmbH.)

Photosynthetic microalgae produce valuable metabolites and are a source of sustainable food that supports life without compromising arable land. However, the light self-shading, excessive water supply, and insufficient space utilization in microalgae farming have limited its potential in the inland areas most in need of regenerative food solutions. Herein, this work develops a 3D polysaccharide-based hydrogel scaffold for vertically farming microalgae without needing liquid media. This liquid-free strategy is compatible with diverse microalgal species and enables the design of living microalgal frameworks with customizable architectures that enhance light and water utilization. This approach significantly increases microalgae yield per unit water consumption, with an 8.8-fold increase compared to traditional methods. Furthermore, the dehydrated hydrogels demonstrate a reduced size and weight (≈70% reduction), but readily recover their vitality upon rehydration. Importantly, valuable natural products can be produced in this system including proteins, carbohydrates, lipids, and carotenoids. This study streamlines microalgae regenerative farming for low-carbon biomanufacturing by minimizing light self-shading, relieving water supply, and reducing physical footprints, and democratizing access to efficient aquatic food production., (© 2024 Wiley‐VCH GmbH.)

A 3D bioprinted neurovascular unit (NVU) model is developed to study glioblastoma (GBM) tumor growth in a brain-like microenvironment. The NVU model includes human primary astrocytes, pericytes and brain microvascular endothelial cells, and patient-derived glioblastoma cells (JHH-520) are used for this study. Fluorescence reporters are used with confocal high content imaging to quantitate real-time microvascular network formation and tumor growth. Extensive validation of the NVU-GBM model includes immunostaining for brain relevant cellular markers and extracellular matrix components; single cell RNA sequencing (scRNAseq) to establish physiologically relevant transcriptomics changes; and secretion of NVU and GBM-relevant cytokines. The scRNAseq reveals changes in gene expression and cytokines secretion associated with wound healing/angiogenesis, including the appearance of an endothelial mesenchymal transition cell population. The NVU-GBM model is used to test 18 chemotherapeutics and anti-cancer drugs to assess the pharmacological relevance of the model and robustness for high throughput screening., (Published 2024. This article is a U.S. Government work and is in the public domain in the USA. Advanced Healthcare Materials published by Wiley‐VCH GmbH.)

Physiologically-relevant in vitro skin models hold the utmost importance for efficacy assessments of pharmaceutical and cosmeceutical formulations, offering valuable alternatives to animal testing. Here, an advanced immunocompetent 3D bioprinted human skin model is presented to assess skin sensitization. Initially, a photopolymerizable bioink is formulated using silk fibroin methacrylate, gelatin methacrylate, and photoactivated human platelet releasate. The developed bioink shows desirable physicochemical and rheological attributes for microextrusion bioprinting. The tunable physical and mechanical properties of bioink are modulated through variable photocuring time for optimization. Thereafter, the bioink is utilized to 3D bioprint "sandwich type" skin construct where an artificial basement membrane supports a biomimetic epidermal layer on one side and a printed pre-vascularized dermal layer on the other side within a transwell system. The printed construct is further cultured in the air-liquid interface for maturation. Immunofluorescence staining demonstrated a differentiated keratinocyte layer and dermal extracellular matrix (ECM)-remodeling by fibroblasts and endothelial cells. The biochemical estimations and gene-expression analysis validate the maturation of the printed model. The incorporation of macrophages further enhances the physiological relevance of the model. This model effectively classifies skin irritative and non-irritative substances, thus establishing itself as a suitable pre-clinical screening platform for sensitization tests., (© 2024 Wiley‐VCH GmbH.)

3D bioprinting techniques have enabled the fabrication of irregular large-sized tissue engineering scaffolds. However, complicated customized designs increase the medical burden. Meanwhile, the integrated printing process hinders the cellular uniform distribution and local angiogenesis. A novel approach is introduced to the construction of sizable tissue engineering grafts by employing hydrogel 3D printing for modular bioadhesion assembly, and a poly (ethylene glycol) diacrylate (PEGDA)-gelatin-dopamine (PGD) hydrogel, photosensitive and adhesive, enabling fine microcage module fabrication via DLP 3D printing is developed. The PGD hydrogel printed micocages are flexible, allowing various shapes and cell/tissue fillings for repairing diverse irregular tissue defects. In vivo experiments demonstrate robust vascularization and superior graft survival in nude mice. This assembly strategy based on scalable 3D printed hydrogel microcage module could simplify the construction of tissue with large volume and complex components, offering promise for diverse large tissue defect repairs., (© 2024 The Authors. Advanced Science published by Wiley‐VCH GmbH.)

Even with the current advancements in wound management, addressing most skin injuries and wounds continues to pose a significant obstacle for the healthcare industry. As a result, researchers are now focusing on creating innovative materials utilizing cellulose and its derivatives. Cellulose, the most abundant biopolymer in nature, has unique properties that make it a promising material for wound healing, such as biocompatibility, tunable physiochemical characteristics, accessibility, and low cost. 3D bioprinting technology has enabled the production of cellulose-based wound dressings with complex structures that mimic the extracellular matrix. The inclusion of bioactive molecules such as growth factors offers the ability to aid in promoting wound healing, while cellulose creates an ideal environment for controlled release of these biomolecules and moisture retention. The use of 3D bioprinted cellulose-based wound dressings has potential benefits for managing chronic wounds, burns, and painful wounds by promoting wound healing and reducing the risk of infection. This review provides an up-to-date summary of cellulose-based dressings manufactured by 3D bioprinting techniques by looking into wound healing biology, biofabrication methods, cellulose derivatives, and the existing cellulose bioinks targeted toward wound healing., (© 2023 The Authors. Macromolecular Bioscience published by Wiley‐VCH GmbH.)

Artificial cells are engineered units with cell-like functions for different purposes including acting as supportive elements for mammalian cells. Artificial cells with minimal liver-like function are made of alginate and equipped with metalloporphyrins that mimic the enzyme activity of a member of the cytochrome P450 family namely CYP1A2. The artificial cells are employed to enhance the dealkylation activity within 3D bioprinted structures composed of HepG2 cells and these artificial cells. This enhancement is monitored through the conversion of resorufin ethyl ether to resorufin. HepG2 cell aggregates are 3D bioprinted using an alginate/gelatin methacryloyl ink, resulting in the successful proliferation of the HepG2 cells. The composite ink made of an alginate/gelatin liquid phase with an increasing amount of artificial cells is characterized. The CYP1A2-like activity of artificial cells is preserved over at least 35 days, where 6 nM resorufin is produced in 8 h. Composite inks made of artificial cells and HepG2 cell aggregates in a liquid phase are used for 3D bioprinting. The HepG2 cells proliferate over 35 days, and the structure has boosted CYP1A2 activity. The integration of artificial cells and their living counterparts into larger 3D semi-synthetic tissues is a step towards exploring bottom-up synthetic biology in tissue engineering., (© 2024 The Authors. Advanced Healthcare Materials published by Wiley‐VCH GmbH.)

Tissue engineered bracket materials provide essential support for the physiological protection and therapeutics of patients. Unfortunately, the implantation process of such devices poses the risk of surgical complications and infection. In this study, an upconversion nanoparticles (UCNPs)-assisted 3D bioprinting approach is developed to realize in vivo molding that is free from invasive surgery. Reasonably designed UCNPs, which convert near-infrared (NIR) photons that penetrate skin tissues into blue-violet emission (300-500 nm), induce a monomer polymerization curing procedure in vivo. Using a fused deposition modeling coordination framework, a precisely predetermined trajectory of the NIR laser enables the manufacture of implantable medical devices with tailored shapes. A proof of the 3D bioprinting of a noninvasive fracture fixation scaffold is achieved successfully, thus demonstrating an entirely new method of in vivo molding for biomedical treatment., (© 2024 Wiley‐VCH GmbH.)

Due to the inherent radiation tolerance, patients who suffered from glioma frequently encounter tumor recurrence and malignant progression within the radiation target area, ultimately succumbing to treatment ineffectiveness. The precise mechanism underlying radiation tolerance remains elusive due to the dearth of in vitro models and the limitations associated with animal models. Therefore, a bioprinted glioma model is engineered, characterized the phenotypic traits in vitro, and the radiation tolerance compared to 2D ones when subjected to X-ray radiation is assessed. By comparing the differential gene expression profiles between the 2D and 3D glioma model, identify functional genes, and analyze distinctions in gene expression patterns. Results showed that 3D glioma models exhibited substantial alterations in the expression of genes associated with the stromal microenvironment, notably a significant increase in the radiation tolerance gene ITGA2 (integrin subunit A2). In 3D glioma models, the knockdown of ITGA2 via shRNA resulted in reduced radiation tolerance in glioma cells and concomitant inhibition of the p-AKT pathway. Overall, 3D bioprinted glioma model faithfully recapitulates the in vivo tumor microenvironment (TME) and exhibits enhanced resistance to radiation, mediated through the ITGA2/p-AKT pathway. This model represents a superior in vitro platform for investigating glioma radiotherapy tolerance., (© 2024 Wiley‐VCH GmbH.)

Advanced in vitro systems such as multicellular spheroids and lab-on-a-chip devices have been developed, but often fall short in reproducing the tissue scale and self-organization of human diseases. A bioprinted artificial tumor model is introduced with endothelial and stromal cells self-organizing into perfusable and functional vascular structures. This model uses 3D hydrogel matrices to embed multicellular tumor spheroids, allowing them to grow to mesoscopic scales and to interact with endothelial cells. It is shown that angiogenic multicellular tumor spheroids promote the growth of a vascular network, which in turn further enhances the growth of cocultivated tumor spheroids. The self-developed vascular structure infiltrates the tumor spheroids, forms functional connections with the bioprinted endothelium, and can be perfused by erythrocytes and polystyrene microspheres. Moreover, cancer cells migrate spontaneously from the tumor spheroid through the self-assembled vascular network into the fluid flow. Additionally, tumor type specific characteristics of desmoplasia, angiogenesis, and metastatic propensity are preserved between patient-derived samples and tumors derived from this same material growing in the bioreactors. Overall, this modular approach opens up new avenues for studying tumor pathophysiology and cellular interactions in vitro, providing a platform for advanced drug testing while reducing the need for in vivo experimentation., (© 2023 The Authors. Advanced Materials published by Wiley-VCH GmbH.)

Osteoarthritis (OA) is a chronic disease that causes pain and disability in adults, affecting ≈300 million people worldwide. It is caused by damage to cartilage, including cellular inflammation and destruction of the extracellular matrix (ECM), leading to limited self-repairing ability due to the lack of blood vessels and nerves in the cartilage tissue. Organoid technology has emerged as a promising approach for cartilage repair, but constructing joint organoids with their complex structures and special mechanisms is still challenging. To overcome these boundaries, 3D bioprinting technology allows for the precise design of physiologically relevant joint organoids, including shape, structure, mechanical properties, cellular arrangement, and biological cues to mimic natural joint tissue. In this review, the authors will introduce the biological structure of joint tissues, summarize key procedures in 3D bioprinting for cartilage repair, and propose strategies for constructing joint organoids using 3D bioprinting. The authors also discuss the challenges of using joint organoids' approaches and perspectives on their future applications, opening opportunities to model joint tissues and response to joint disease treatment., (© 2023 Wiley-VCH GmbH.)

Biomaterials are extensively used to mimic cell-matrix interactions, which are essential for cell growth, function, and differentiation. This is particularly relevant when developing in vitro disease models of organs rich in extracellular matrix, like the liver. Liver disease involves a chronic wound-healing response with formation of scar tissue known as fibrosis. At early stages, liver disease can be reverted, but as disease progresses, reversion is no longer possible, and there is no cure. Research for new therapies is hampered by the lack of adequate models that replicate the mechanical properties and biochemical stimuli present in the fibrotic liver. Fibrosis is associated with changes in the composition of the extracellular matrix that directly influence cell behavior. Biomaterials could play an essential role in better emulating the disease microenvironment. In this paper, the recent and cutting-edge biomaterials used for creating in vitro models of human liver fibrosis are revised, in combination with cells, bioprinting, and/or microfluidics. These technologies have been instrumental to replicate the intricate structure of the unhealthy tissue and promote medium perfusion that improves cell growth and function, respectively. A comprehensive analysis of the impact of material hints and cell-material interactions in a tridimensional context is provided., (© 2023 Wiley-VCH GmbH.)

Methods accurately predicting the responses of colorectal cancer (CRC) and colorectal cancer liver metastasis (CRLM) to personalized chemotherapy remain limited due to tumor heterogeneity. This study introduces an innovative patient-derived CRC and CRLM tumor model for preclinical investigation, utilizing 3d-bioprinting (3DP) technology. Efficient construction of homogeneous in vitro 3D models of CRC/CRLM is achieved through the application of patient-derived primary tumor cells and 3D bioprinting with bioink. Genomic and histological analyses affirm that the CRC/CRLM 3DP tumor models effectively retain parental tumor biomarkers and mutation profiles. In vitro tests evaluating chemotherapeutic drug sensitivities reveal substantial tumor heterogeneity in chemotherapy responses within the 3DP CRC/CRLM models. Furthermore, a robust correlation is evident between the drug response in the CRLM 3DP model and the clinical outcomes of neoadjuvant chemotherapy. These findings imply a significant potential for the application of patient-derived 3DP cancer models in precision chemotherapy prediction and preclinical research for CRC/CRLM., (© 2023 The Authors. Advanced Science published by Wiley-VCH GmbH.)

While the human body has many different examples of perfusable structures with complex geometries, biofabrication methods to replicate this complexity are still lacking. Specifically, the fabrication of self-supporting, branched networks with multiple channel diameters is particularly challenging. Here, we present the Gelation of Uniform Interfacial Diffusant in Embedded 3D Printing (GUIDE-3DP) approach for constructing perfusable networks of interconnected channels with precise control over branching geometries and vessel sizes. To achieve user-specified channel dimensions, this technique leverages the predictable diffusion of crosslinking reaction-initiators released from sacrificial inks printed within a hydrogel precursor. We demonstrate the versatility of GUIDE-3DP to be adapted for use with diverse physicochemical crosslinking mechanisms by designing seven printable material systems. Importantly, GUIDE-3DP allows for the independent tunability of both the inner and outer diameters of the printed channels and the ability to fabricate seamless junctions at branch points. This 3D bioprinting platform is uniquely suited for fabricating lumenized structures with complex shapes characteristic of multiple hollow vessels throughout the body. As an exemplary application, we demonstrate the fabrication of vasculature-like networks lined with endothelial cells. GUIDE-3DP represents an important advance toward the fabrication of self-supporting, physiologically relevant networks with intricate and perfusable geometries., Competing Interests: Conflict of Interest S.S., J.G.R., A.J.S., and S.C.H. are inventors on a non-provisional patent application (no. 18/142,931, filed 3 May 2023) related to this work, submitted by the Board of Trustees of Stanford University.

Several microfabrication technologies have been used to engineer native-like skeletal muscle tissues. However, the successful development of muscle remains a significant challenge in the tissue engineering field. Muscle tissue engineering aims to combine muscle precursor cells aligned within a highly organized 3D structure and biological factors crucial to support cell differentiation and maturation into functional myotubes and myofibers. In this study, the use of 3D bioprinting is proposed for the fabrication of muscle tissues using gelatin methacryloyl (GelMA) incorporating sustained insulin-like growth factor-1 (IGF-1)-releasing microparticles and myoblast cells. This study hypothesizes that functional and mature myotubes will be obtained more efficiently using a bioink that can release IGF-1 sustainably for in vitro muscle engineering. Synthesized microfluidic-assisted polymeric microparticles demonstrate successful adsorption of IGF-1 and sustained release of IGF-1 at physiological pH for at least 21 days. Incorporating the IGF-1-releasing microparticles in the GelMA bioink assisted in promoting the alignment of myoblasts and differentiation into myotubes. Furthermore, the myotubes show spontaneous contraction in the muscle constructs bioprinted with IGF-1-releasing bioink. The proposed bioprinting strategy aims to improve the development of new therapies applied to the regeneration and maturation of muscle tissues., (© 2023 Wiley-VCH GmbH.)

The meniscus plays a crucial role in loads distribution and protection of articular cartilage. Meniscal injury can result in cartilage degeneration, loss of mechanical stability in the knee joint and ultimately lead to arthritis. Surgical interventions provide only short-term pain relief but fail to repair or regenerate the injured meniscus. Emerging tissue engineering approaches based on 3D bioprinting provide alternatives to current surgical methods for meniscus repair. In this review, the current bioprinting techniques employed in developing engineered meniscus grafts are summarized and discuss the latest strategies for mimicking the gradient structure, composition, and viscoelastic properties of native meniscus. Recent progress is highlighted in gene-activated matrices for meniscus regeneration as well. Finally, a perspective is provided on the future development of 3D bioprinting for meniscus repair, emphasizing the potential of this technology to revolutionize meniscus regeneration and improve patient outcomes., (© 2023 Wiley-VCH GmbH.)

3D bioprinting is revolutionizing the fields of personalized and precision medicine by enabling the manufacturing of bioartificial implants that recapitulate the structural and functional characteristics of native tissues. However, the lack of quantitative and noninvasive techniques to longitudinally track the function of implants has hampered clinical applications of bioprinted scaffolds. In this study, multimaterial 3D bioprinting, engineered nanoparticles (NPs), and spectral photon-counting computed tomography (PCCT) technologies are integrated for the aim of developing a new precision medicine approach to custom-engineer scaffolds with traceability. Multiple CT-visible hydrogel-based bioinks, containing distinct molecular (iodine and gadolinium) and NP (iodine-loaded liposome, gold, methacrylated gold (AuMA), and Gd 2 O 3 ) contrast agents, are used to bioprint scaffolds with varying geometries at adequate fidelity levels. In vitro release studies, together with printing fidelity, mechanical, and biocompatibility tests identified AuMA and Gd 2 O 3 NPs as optimal reagents to track bioprinted constructs. Spectral PCCT imaging of scaffolds in vitro and subcutaneous implants in mice enabled noninvasive material discrimination and contrast agent quantification. Together, these results establish a novel theranostic platform with high precision, tunability, throughput, and reproducibility and open new prospects for a broad range of applications in the field of precision and personalized regenerative medicine., (© 2023 Wiley-VCH GmbH.)

Advances in bioprinting have enabled the fabrication of complex tissue constructs with high speed and resolution. However, there remains significant structural and biological complexity within tissues that bioprinting is unable to recapitulate. Bone, for example, has a hierarchical organization ranging from the molecular to whole organ level. Current bioprinting techniques and the materials employed have imposed limits on the scale, speed, and resolution that can be achieved, rendering the technique unable to reproduce the structural hierarchies and cell-matrix interactions that are observed in bone. The shift toward biomimetic approaches in bone tissue engineering, where hydrogels provide biophysical and biochemical cues to encapsulated cells, is a promising approach to enhancing the biological function and development of tissues for in vitro modeling. A major focus in bioprinting of bone tissue for in vitro modeling is creating dynamic microenvironmental niches to support, stimulate, and direct the cellular processes for bone formation and remodeling. Hydrogels are ideal materials for imitating the extracellular matrix since they can be engineered to present various cues whilst allowing bioprinting. Here, recent advances in hydrogels and 3D bioprinting toward creating a microenvironmental niche that is conducive to tissue engineering of in vitro models of bone are reviewed., (© 2023 The Authors. Advanced Materials published by Wiley-VCH GmbH.)

Intra-portal islet transplantation is currently the only clinically approved beta cell replacement therapy, but its outcome is hindered by limited cell survival due to a multifactorial reaction against the allogeneic tissue in liver. Adipose-derived stromal cells (ASCs) can potentially improve the islet micro-environment by their immunomodulatory action. The challenge is to combine both islets and ASCs in a relatively easy and consistent long-term manner in a deliverable scaffold. Manufacturing the 3D bioprinted double-layered scaffolds with primary islets and ASCs using a mix of alginate/nanofibrillated cellulose (NFC) bioink is reported. The diffusion properties of the bioink and the supportive effect of human ASCs on islet viability, glucose sensing, insulin secretion, and reducing the secretion of pro-inflammatory cytokines are demonstrated. Diabetic mice transplanted with islet-ASC scaffolds reach normoglycemia seven days post-transplantation with no significant difference between this group and the group received islets under the kidney capsules. In addition, animals transplanted with islet-ASC scaffolds stay normoglycemic and show elevated levels of C-peptide compared to mice transplanted with islet-only scaffolds. The data present a functional 3D bioprinted scaffold for islets and ASCs transplanted to the extrahepatic site and suggest a possible role of ASCs on improving the islet micro-environment., (© 2023 The Authors. Advanced Healthcare Materials published by Wiley-VCH GmbH.)

The availability of grafts to replace small-diameter arteries remains an unmet clinical need. Here, the validated methodology is reported for a novel hybrid tissue-engineered vascular graft that aims to match the natural structure of small-size arteries. The blood vessel mimic (BVM) comprises an internal conduit of co-electrospun gelatin and polycaprolactone (PCL) nanofibers (corresponding to the tunica intima of an artery), reinforced by an additional layer of PCL aligned fibers (the internal elastic membrane). Endothelial cells are deposited onto the luminal surface using a rotative bioreactor. A bioprinting system extrudes two concentric cell-laden hydrogel layers containing respectively vascular smooth muscle cells and pericytes to create the tunica media and adventitia. The semi-automated cellularization process reduces the production and maturation time to 6 days. After the evaluation of mechanical properties, cellular viability, hemocompatibility, and suturability, the BVM is successfully implanted in the left pulmonary artery of swine. Here, the BVM showed good hemostatic properties, capability to withstand blood pressure, and patency at 5 weeks post-implantation. These promising data open a new avenue to developing an artery-like product for reconstructing small-diameter blood vessels., Competing Interests: Conflict of Interest The authors declare no conflict of interest.

Injectable hydrogels are increasingly explored for the delivery of cells to tissue. These materials exhibit both liquid-like properties, protecting cells from mechanical stress during injection, and solid-like properties, providing a stable 3D engraftment niche. Many strategies for modulating injectable hydrogels tune liquid- and solid-like material properties simultaneously, such that formulation changes designed to improve injectability can reduce stability at the delivery site. The ability to independently tune liquid- and solid-like properties would greatly facilitate formulation development. Here, such a strategy is presented in which cells are ensconced in the pores between microscopic granular hyaluronic acid (HA) hydrogels (microgels), where elasticity is tuned with static covalent intra-microgel crosslinks and flowability with mechanosensitive adamantane-cyclodextrin (AC) inter-microgel crosslinks. Using the same AC-free microgels as a 3D printing support bath, the location of each cell is preserved as it exits the needle, allowing identification of the mechanism driving mechanical trauma-induced cell death. The microgel AC concentration is varied to find the threshold from microgel yielding- to AC interaction-dominated injectability, and this threshold is exploited to fabricate a microgel with better injection-protecting performance. This delivery strategy, and the balance between intra- and inter-microgel properties it reveals, may facilitate the development of new cell injection formulations., (© 2023 Wiley-VCH GmbH.)

Many mammalian tissues adopt a specific cellular arrangement under stress stimulus that enables their unique function. However, conventional 3D encapsulation often fails to recapitulate the complexities of these arrangements, thus motivating the need for advanced cellular arrangement approaches. Here, an original 3D prestress bioprinting approach of directed tissues under the synergistic effect of static sustained tensile stress and molecular chain orientation, with an aid of slow crosslinking in bioink, is developed. The semi-crosslinking state of the designed bioink exhibits excellent elasticity for applying stress on the cells during the sewing-like process. After bioprinting, the bioink gradually forms complete crosslinking and keeps the applied stress force to induce cell-orientated growth. More importantly, multiple cell types can be arranged directionally by this approach, while the internal stress of the hydrogel filament is also adjustable. In addition, compared with conventional bioprinted skin, the 3D prestress bioprinted skin results in a better wound healing effect due to promoting the angiogenesis of granulation tissue. This study provides a prospective strategy to engineer skeletal muscles, as well as tendons, ligaments, vascular networks, or combinations thereof in the future., (© 2023 Wiley-VCH GmbH.)

In vitro neurovascular unit (NVU) models are valuable for investigating brain functions and developing drugs. However, it remains challenging to recapitulate the native architectural features and ultra-soft extracellular matrix (ECM) properties of the natural NVU. Cell-laden bioprinting is promising to prepare complex living tissues, but hard to balance the fidelity and cell growth. This study proposes a novel two-stage methodology for biomanufacturing functional 3D neurovascular constructs in vitro with low modulus of ECM. At the shaping stage, a low-viscosity alginate/collagen is printed through an embedded approach; at the culturing stage, the alginate is removed through targeted lysing. The low-viscosity and rapid crosslinking properties provide a printing resolution of ≈10 µm, and the lysis processing can decrease the hydrogels' modulus to ≈1 kPa and adjust the porosity of the microstructure, providing cells with an environment closing to the brain ECM. A 3D hollow coaxial neurovascular model is fabricated, in which the endothelial cells has expressed tight junction proteins and shown selective permeability, and the astrocytes outside of the endothelial layer are found to spread out with branches and directly interact with endothelial cells. The present study offers a promising modeling method for better understanding the NVU function and screening neuro-drugs., (© 2023 The Authors. Advanced Healthcare Materials published by Wiley-VCH GmbH.)

Successful integration of cell-laden tissue constructs with host vasculature depends on the presence of functional capillaries to provide oxygen and nutrients to the embedded cells. However, diffusion limitations of cell-laden biomaterials challenge regeneration of large tissue defects that require bulk-delivery of hydrogels and cells. Herein, a strategy to bioprint geometrically controlled, endothelial and stem-cell laden microgels in high-throughput is introduced, allowing these cells to form mature and functional pericyte-supported vascular capillaries in vitro, and then injecting these pre-vascularized constructs minimally invasively in-vivo. It is demonstrated that this approach offers both desired scalability for translational applications as well as unprecedented levels of control over multiple microgel parameters to design spatially-tailored microenvironments for better scaffold functionality and vasculature formation. As a proof-of-concept, the regenerative capacity of the bioprinted pre-vascularized microgels is compared with that of cell-laden monolithic hydrogels of the same cellular and matrix composition in hard-to-heal defects in vivo. The results demonstrate that the bioprinted microgels have faster and higher connective tissue formation, more vessels per area, and widespread presence of functional chimeric (human and murine) vascular capillaries across regenerated sites. The proposed strategy, therefore, addresses a significant issue in regenerative medicine, demonstrating a superior potential to facilitate translational regenerative efforts., (© 2023 Wiley-VCH GmbH.)

Currently, the demand for more reliable drug screening devices has made scientists and researchers develop novel potential approaches to offer an alternative to animal studies. Organ-on-chips are newly emerged platforms for drug screening and disease metabolism investigation. These microfluidic devices attempt to recapitulate the physiological and biological properties of different organs and tissues using human-derived cells. Recently, the synergistic combination of additive manufacturing and microfluidics has shown a promising impact on improving a wide array of biological models. In this review, different methods are classified using bioprinting to achieve the relevant biomimetic models in organ-on-chips, boosting the efficiency of these devices to produce more reliable data for drug investigations. In addition to the tissue models, the influence of additive manufacturing on microfluidic chip fabrication is discussed, and their biomedical applications are reviewed., (© 2023 The Authors. Advanced Healthcare Materials published by Wiley-VCH GmbH.)