Bioprinting Strategy Research Articles

3D Bioprinting of Thick Adipose Tissues with Integrated Vascular Hierarchies

AbstractEngineering functional, thick tissues with integrated vascular architectures is crucial for advancing regenerative medicine. This study applied a novel 3D bioprinting strategy to construct thick adipose tissues featuring complex, hierarchical vascular networks. Mature adipocytes and endothelial cells are encapsulated within a collagen matrix, with structural integrity and vascular functionality ensured through a combination of bioinks. An innovative approach is utilized to establish millimetric vascular channels that connect to microvascular networks, forming a fully perfusable, hierarchical vasculature throughout the 3D bioprinted tissue. The structural stability and endothelial functionality of the vascularized constructs are assessed under continuous flow. In‐vitro analyses confirmed the integrity of the vascular networks and demonstrated the functional characteristics of the printed mature adipose cells. Direct anastomosis of the bioprinted tissue to a rat femoral artery resulted in effective vascular integration and tissue viability, as evidenced by efficient blood perfusion and significant host vascular ingrowth within the implanted tissues. The findings highlighted the potential of the presented bioprinting technique in the development of fully functional, vascularized adipose tissues suitable for surgical reconstruction and regenerative medicine applications.

3D Bioprinting of Liquid High-Cell-Proportion Bioinks in Liquid Granular Bath.

Embedded 3D bioprinting techniques have emerged as a powerful method to fabricate 3D engineered constructsusing 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.

Hybrid biofabricated blood vessel for medical devices testing

ABSTRACT Current in vitro and in vivo tests applied to assess the safety of medical devices retain several limitations, such as an incomplete ability to faithfully recapitulate human features, and to predict the response of human tissues together with non-trivial ethical aspects. We here challenged a new hybrid biofabrication technique that combines bioprinting and Fast Diffusion-induced Gelation strategy to generate a vessel-like structure with the attempt to spatially organize fibroblasts, smooth-muscle cells, and endothelial cells. The introduction of Fast Diffusion-induced Gelation minimizes the endothelial cell mortality during biofabrication and produce a thin endothelial layer with tunable thickness. Cell viability, Von Willebrand factor, and CD31 expression were evaluated on biofabricated tissues, showing how bioprinting and Fast Diffusion-induced Gelation can replicate human vessels architecture and complexity. We then applied biofabricated tissue to study the cytotoxicity of a carbothane catheter under static condition, and to better recapitulate the effect of blood flow, a novel bioreactor named CuBiBox (Customized Biological Box) was developed and introduced in a dynamic modality. Collectively, we propose a novel bioprinted platform for human in vitro biocompatibility testing, predicting the impact of medical devices and their materials on vascular systems, reducing animal experimentation and, ultimately, accelerating time to market.

Natural bioink of interpenetrating network hydrogels mimicking extracellular polymeric substances for microbial immobilization in water pollution control

Artificial biomanufacturing has been developed as a promising biotechnology for water pollution control. Effective bioimmobilization techniques are limited in application because of low productivity and the difficulty in achieving both mechanical strength and biocompatibility. Bioprinting technology, using biomaterials as bioink to enable the rapid on-demand production of bioactive structures, opens a new path for bioimmobilization. In this study, mimicking extracellular polysaccharide and protein of aerobic granular sludge (AGS), sodium alginate (SA) and silk fibroin methacryloyl (SilMA) were developed as the dual-component bioink with a suitable viscosity for bioprinting hydrogel. Interpenetrating network (IPN) hydrogel beads were manufactured using 1.5% (w/v) SA combined with 20% (w/v) SilMA through physical and covalent crosslinking, which exhibited excellent structural stability and bioactivity. The addition of SilMA provided a solution to the poor mechanical stability of SA-Ca hydrogels limited by Ca2+-Na+ ionic exchange. The unique structure of SilMA contributed to the reduction of hydrogel swelling as well as the prevention of SA loss. IPN hydrogels showed a swelling rate of less than 20% compared to the high swelling rate of more than 60% for SA hydrogels. On the other hand, SA controlled the hardening induced by excessive self-assembly of SilMA and improved mass transport in SilMA hydrogels. Compared to IPN hydrogels, SilMA hydrogels experienced a 15% volumetric shrinkage and exhibited a low water content of 92%. Sonication pretreatment of the dual-component bioink not only increased the intermolecular chain entanglement to form IPN, but also led to β-sheet content in SiMA reaching 46%–48%, which resulted in the formation of stable IPN hydrogels dominated entirely by physical crosslinking. Satisfactory proliferation and viability were achieved for the encapsulated bacteria in IPN hydrogels (μmax 1.49–2.18 d−1). Further, the IPN biohydrogels could maintain structural stability as well as achieve pollutant removal for treating synthetic wastewater with high Na+ concentration of 300 mg/L. The novel SA/SilMA hydrogel bioprinting strategy established in this study offers a new direction for bioimmobilization in water pollution control and other environmental applications.

In vitro three-dimensional volumetric printing of vitreous body models using decellularized extracellular matrix bioink

Hyalocytes, which are considered to originate from the monocyte/macrophage lineage, play active roles in vitreous collagen and hyaluronic acid synthesis. Obtaining a hyalocyte-compatible bioink during the 3D bioprinting of eye models is challenging. In this study, we investigated the suitability of a cartilage-decellularized extracellular matrix (dECM)-based bioink for printing a vitreous body model. Given that achieving a 3D structure and environment identical to those of the vitreous body necessitates good printability and biocompatibility, we examined the mechanical and biological properties of the developed dECM-based bioink. Furthermore, we proposed a 3D bioprinting strategy for volumetric vitreous body fabrication that supports cell viability, transparency, and self-sustainability. The construction of a 3D structure composed of bioink microfibers resulted in improved transparency and hyalocyte-like macrophage activity in volumetric vitreous mimetics, mimicking real vitreous bodies. The results indicate that our 3D structure could serve as a platform for drug testing in disease models and demonstrate that the proposed printing technology, utilizing a dECM-based bioink and volumetric vitreous body, has the potential to facilitate the development of advanced eye models for future studies on floater formation and visual disorders.

Bioprinting with superelastic and fatigue-resistant bioinks for large-sized tissue delivery

3D bioprinting technology is advancing rapidly to construct multi-scale preformed architectures that satisfy the demands of tissue regeneration. However, challenges remain in accurately delivering large-sized preformed architectures to the defect sites without being damaged by the mechanical environment in vivo. In this study, we proposed a versatile bioprinting strategy to fabricate large-sized architectures with remarkable injection capacity for geometry-independent minimally invasive tissue delivery. We design a novel hydrogel by mixing gelatin methacryloyl with poly(ethylene glycol) diacrylate (PEGDA) and photocrosslinking the mixture under a white light source. The hydrogel forms a reinforced crosslinking network, exhibiting superelasticity and fatigue resistance. We infer that the flexible chains of high-molecular-weight PEGDA and interconnected macropores of hydrogel contribute to the reinforcement mechanisms. With a decoupled bioprinting strategy, the bioink can be 3D printed into large-sized architectures with different geometries and tunable Poisson’s ratio. The printing architectures displayed excellent deformation and shape recovery capacity by compressing to less than 1% of the original size and fully recovering after injection. The injection capacity is geometry-independent, indicating the intrinsic properties of the hydrogel and allowing higher freedom for the structural design and geometry size of the architectures. The bioprinting process is compatible with genome-edited hepatic cells with high cell-bioprinting suitability, demonstrating high cell viability, a minimally altered transcriptomic profile after bioprinting, and a biocompatible microenvironment that supports cell survival and hepatic function maintenance. The cell-laden architectures express uncompromised injection capacity with unaffected cell viability after injection. This study presents a generalizable strategy for preparing and bioprinting with superelastic and fatigue-resistant bioinks into customized cell-laden architectures to facilitate minimally invasive large-sized tissue delivery.

Coaxial Electrohydrodynamic Bioprinting of Pre-vascularized Cell-laden Constructs for Tissue Engineering.

Recapitulating the vascular networks that maintain the delivery of nutrition, oxygen, and byproducts for the living cells within the three-dimensional (3D) tissue constructs is a challenging issue in the tissue-engineering area. Here, a novel coaxial electrohydrodynamic (EHD) bioprinting strategy is presented to fabricate thick pre-vascularized cell-laden constructs. The alginate and collagen/calcium chloride solution were utilized as the outer-layer and inner-layer bioink, respectively, in the coaxial printing nozzle to produce the core-sheath hydrogel filaments. The effect of process parameters (the feeding rate of alginate and collagen and the moving speed of the printing stage) on the size of core and sheath lines within the printed filaments was investigated. The core-sheath filaments were printed in the predefined pattern to fabricate lattice hydrogel with perfusable lumen structures. Endothelialized lumen structures were fabricated by culturing the core-sheath filaments with endothelial cells laden in the core collagen hydrogel. Multilayer core-sheath filaments were successfully printed into 3D porous hydrogel constructs with a thickness of more than 3 mm. Finally, 3D pre-vascularized cardiac constructs were successfully generated, indicating the efficacy of our strategy to engineer living tissues with complex vascular structures.

Embedded Bioprinting of Tissue-like Structures Using κ-Carrageenan Sub-Microgel Medium.

Embedded three-dimensional (3D) bioprinting utilizing a granular hydrogel supporting bath has emerged as a critical technique for creating biomimetic scaffolds. However, engineering a suitable gel suspension medium that balances precise bioink deposition with cell viability and function presents multiple challenges, particularly in achieving the desired viscoelastic properties. Here, a novel κ-carrageenan gel supporting bath is fabricated through an easy-to-operate mechanical grinding process, producing homogeneous sub-microscale particles. These sub-microgels exhibit typical Bingham flow behavior with small yield stress and rapid shear-thinning properties, which facilitate the smooth deposition of bioinks. Moreover, the reversible gel-sol transition and self-healing capabilities of the κ-carrageenan microgel network ensure the structural integrity of printed constructs, enabling the creation of complex, multi-layered tissue structures with defined architectural features. Post-printing, the κ-carrageenan sub-microgels can be easily removed by a simple phosphate-buffered saline wash. Further bioprinting with cell-laden bioinks demonstrates that cells within the biomimetic constructs have a high viability of 92% and quickly extend pseudopodia, as well as maintain robust proliferation, indicating the potential of this bioprinting strategy for tissue and organ fabrication. In summary, this novel κ-carrageenan sub-microgel medium emerges as a promising avenue for embedded bioprinting of exceptional quality, bearing profound implications for the in vitro development of engineered tissues and organs.

Direct Fabrication of Glycoengineered Cells via Photoresponsive Thiol-ene Reaction.

Three-dimensional printing of cell constructs with high-cell density, shape fidelity, and heterogeneous cell populations is an important tool for investigating cell sociology in living tissues but remains challenging. Herein, we propose an artificial intercellular adhesion method using a photoresponsive chemical cue between a thiol-bearing polymer and a methacrylate-bearing cell membrane. This process provided cell fabrication containing 108 cells/mL, embedded multiple cell populations in one structure, and enabled millimeter-sized scaleup. Our approach allows for the artificial cell construction of complex structures and is a promising bioprinting strategy for engineering tissues that are structurally and physiologically relevant.

Embedded bioprinted multicellular spheroids modeling pancreatic cancer bioarchitecture towards advanced drug therapy.

The desmoplastic bioarchitecture and microenvironment caused by fibroblasts have been confirmed to be closely related to the drug response behavior of pancreatic ductal adenocarcinoma (PDAC). Despite the extensive progress in developing PDAC models as in vitro drug screening platforms, developing efficient and controllable approaches for the construction of physiologically relevant models remains challenging. In the current study, multicellular spheroid models that emulate pancreatic cancer bioarchitecture and the desmoplastic microenvironment are bioengineered. An extrusion-based embedded dot bioprinting strategy was established to fabricate PDAC spheroids in a one-step process. Cell-laden hydrogel beads were directly deposited into a methacrylated gelatin (GelMA) suspension bath to generate spherical multicellular aggregates (SMAs), which further progressed into dense spheroids through in situ self assembly. By modulating the printing parameters, SMAs, even from multiple cell components, could be manipulated with tunable size and flexible location, achieving tunable spheroid patterns within the hydrogel bath with reproducible morphological features. To demonstrate the feasibility of this printing strategy, we fabricated desmoplastic PDAC spheroids by printing SMAs consisting of tumor cells and fibroblasts within the GelMA matrix bath. The produced hybrid spheroids were further exposed to different concentrations of the drug gemcitabine to verify their potential for use in cell therapy. Beyond providing a robust and facile bioprinting system that enables desmoplastic PDAC bioarchitecture bioengineering, this work introduces an approach for the scalable, flexible and rapid fabrication of cell spheroids or multi-cell-type spheroid patterns as platforms for advanced drug therapy or disease mechanism exploration.

Novel strategy for multi-material 3D bioprinting of human stem cell based corneal stroma with heterogenous design

Three-dimensional (3D) bioprinting offers an automated, customizable solution to manufacture highly detailed 3D tissue constructs and holds great promise for regenerative medicine to solve the severe global shortage of donor tissues and organs. However, uni-material 3D bioprinting is not sufficient for manufacturing heterogenous 3D constructs with native-like microstructures and thus, innovative multi-material solutions are required. Here, we developed a novel multi-material 3D bioprinting strategy for bioprinting human corneal stroma. The human cornea is the transparent outer layer of your eye, and vision loss due to corneal blindness has serious effects on the quality of life of individuals. One of the main reasons for corneal blindness is the damage in the detailed organization of the corneal stroma where collagen fibrils are arranged in layers perpendicular to each other and the corneal stromal cells grow along the fibrils. Donor corneas for treating corneal blindness are scarce, and the current tissue engineering (TE) technologies cannot produce artificial corneas with the complex microstructure of native corneal stroma. To address this, we developed a novel multi-material 3D bioprinting strategy to mimic detailed organization of corneal stroma. These multi-material 3D structures with heterogenous design were bioprinted by using human adipose tissue -derived stem cells (hASCs) and hyaluronic acid (HA) -based bioinks with varying stiffnesses. In our novel design of 3D models, acellular stiffer HA-bioink and cell-laden softer HA-bioink were printed in alternating filaments, and the filaments were printed perpendicularly in alternating layers. The multi-material bioprinting strategy was applied for the first time in corneal stroma 3D bioprinting to mimic the native microstructure. As a result, the soft bioink promoted cellular growth and tissue formation of hASCs in the multi-material 3D bioprinted composites, whereas the stiff bioink provided mechanical support as well as guidance of cellular organization upon culture. Interestingly, cellular growth and tissue formation altered the mechanical properties of the bioprinted composite constructs significantly. Importantly, the bioprinted composite structures showed good integration to the host tissue in ex vivo cornea organ culture model. As a conclusion, the developed multi-material bioprinting strategy provides great potential as a biofabrication solution for manufacturing organized, heterogenous microstructures of native tissues. To the best of our knowledge, this multi-material bioprinting strategy has never been applied in corneal bioprinting. Therefore, our work advances the technological achievements in additive manufacturing and brings the field of corneal TE to a new level.

Smart Design for Hybrid Bioprinting of Scalable and Viable Tissue Constructs.

Hybrid bioprinting uses sequential printing of melt-extruded biodegradable thermoplastic polymer and cell-encapsulated bioink in a predesigned manner using high- and low-temperature print heads for the fabrication of robust three-dimensional (3D) biological constructs. However, the high-temperature print head and melt-extruded polymer cause irreversible thermal damage to the bioprinted cells, and it affects viability and functionality of 3D bioprinted biological constructs. Thus, there is an urgent need to develop innovative approaches to protect the bioprinted cells, coming into contact or at close proximities to the melt-extruded thermoplastic polymer and the high-temperature print head during hybrid bioprinting. Therefore, this study investigated the potential of iterating the structural architecture pattern (SAP) of melt-printed thermoplastic layers and the cell printing pattern (CPP) to protect the cells from temperature-associated damage during hybrid bioprinting. A novel SAP for printing the thermoplastic polymer and an associated CPP for minimizing thermal damage to the 3D bioprinted construct have been developed. The newly developed SAP- and CPP-based hybrid bioprinted biological constructs showed significantly low thermal damage compared to conventionally hybrid bioprinted biological constructs. The results from this study suggest that the newly developed SAP and CPP can be an improved hybrid bioprinting strategy for developing living constructs at the human scale.

Enhancing Craniofacial Bone Reconstruction with Clinically Applicable 3D Bioprinted Constructs.

Medical imaging and 3D bioprinting can be used to create patient-specific bone scaffolds with complex shapes and controlled inner architectures. This study investigated the effectiveness of a biomimetic approach to scaffold design by employing geometric control. The biomimetic scaffold with a dense external layer showed improved bone regeneration compared to the control scaffold. New bone filled the defected region in the biomimetic scaffolds, while the control scaffolds only presented new bone at the boundary. Histological examination also shows effective bone regeneration in the biomimetic scaffolds, while fibrotic tissue ingrowth is observed in the control scaffolds. These findings suggest that the biomimetic bone scaffold, designed to minimize competition for fibrotic tissue formation in the bony defect, can enhance bone regeneration. This study underscores the notion that patient-specific anatomy can be accurately translated into a 3D bioprinting strategy through medical imaging, leading to the fabrication of constructs with significant clinical relevance.

Triaxial bioprinting large-size vascularized constructs with nutrient channels

Bioprinting has demonstrated great advantages in tissue and organ regeneration. However, constructing large-scale tissue and organs in vitro is still a huge challenge due to the lack of some strategies for loading multiple types of cells precisely while maintaining nutrient channels. Here, a new 3D bioprinting strategy was proposed to construct large-scale vascularized tissue. A mixture of gelatin methacrylate (GelMA) and sodium alginate (Alg) was used as a bioink, serving as the outer and middle layers of a single filament in the triaxial printing process, and loaded with human bone marrow mesenchymal stem cells and human umbilical vein endothelial cells, respectively, while a calcium chloride (CaCl2) solution was used as the inner layer. The CaCl2 solution crosslinked with the middle layer bioink during the printing process to form and maintain hollow nutrient channels, then a stable large-scale construct was obtained through photopolymerization and ion crosslinking after printing. The feasibility of this strategy was verified by investigating the properties of the bioink and construct, and the biological performance of the vascularized construct. The results showed that a mixture of 5% (w/v) GelMA and 1% (w/v) Alg bioink could be printed at room temperature with good printability and perfusion capacity. Then, the construct with and without channels was fabricated and characterized, and the results revealed that the construct with channels had a similar degradation profile to that without channels, but lower compressive modulus and higher swelling rate. Biological investigation showed that the construct with channels was more favorable for cell survival, proliferation, diffusion, migration, and vascular network formation. In summary, it was demonstrated that constructing large-scale vascularized tissue by triaxial printing that can precisely encapsulate multiple types of cells and form nutrient channels simultaneously was feasible, and this technology could be used to prepare large-scale vascularized constructs.

Sequentially suspended 3D bioprinting of multiple-layered vascular models with tunable geometries forin vitromodeling of arterial disorders initiation.

As the main precursor of arterial disorders, endothelial dysfunction preferentially occurs in regions of arteries prone to generating turbulent flow, particularly in branched regions of vasculatures. Although various diseased models have been engineered to investigate arterial pathology, producing a multiple-layered vascular model with branched geometries that can recapitulate the critical physiological environments of human arteries, such as intercellular communications and local turbulent flows, remains challenging. This study develops a sequentially suspended three-dimensional bioprinting (SSB) strategy and a visible-light-curable decellularized extracellular matrix bioink (abbreviated as 'VCD bioink') to construct a biomimetic human arterial model with tunable geometries. The engineered multiple-layered arterial models with compartmentalized vascular cells can exhibit physiological functionality and pathological performance under defined physiological flows specified by computational fluid dynamics simulation. Using different configurations of the vascular models, we investigated the independent and synergetic effects of cellular crosstalk and abnormal hemodynamics on the initiation of endothelial dysfunction, a hallmark event of arterial disorder. The results suggest that the arterial model constructed using the SSB strategy and VCD bioinks has promise in establishing diagnostic/analytic platforms for understanding the pathophysiology of human arterial disorders and relevant abnormalities, such as atherosclerosis, aneurysms, and ischemic diseases.

Enhanced Maturation of 3D Bioprinted Skeletal Muscle Tissue Constructs Encapsulating Soluble Factor-Releasing Microparticles.

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 21days. 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.

4d Bioprinting via Molecular Network Contraction for Membranous Tissue Fabrication.

Generation of thin membranous tissues (TMT), such as the cornea, epidermis, and periosteum, presents a difficult fabrication challenge in tissue engineering (TE). TMTs consist of several cell layers that are less than 100μm in thickness per layer. While traditional methods provide the necessary resolution for TMT fabrication, they require significant handling and incorporation of several layers is limited. Extrusion bioprinting offers precise control over deposition of different biomaterials and cell populations within the same construct but lacks the resolution to generate biomimetic TMTs. W e have developed, for the first time, a 4D bioprinting strategy that allows for the generation of cell-laden TMTs. Anionic gelatin methacrylate (GelMA) hydrogels are treated with cationic poly-L-lysine (PLL), which induces charge attraction, microscale network collapse, and macroscale hydrogel shrinking. The impact of shrinking on hydrogel properties, print resolution, and cell viability are presented. Additionally, o ur work suggests that a novel mechanism is occurring, where PLL exhibits a contractile force on GelMA and PLL molecular weight drives GelMA shrinking capabilities. Finally, w e show that this phenomenon can occur while maintaining an encapsulated cell population. These findings address a critical barrier in TE by generating macroscale tissue structures with their microscale TMT counterparts in the same print. This article is protected by copyright. All rights reserved.

A bioactive microparticle-loaded osteogenically enhanced bioprinted scaffold that permits sustained release of BMP-2.

Extrusion-based bioprinting technology is widely used for tissue regeneration and reconstruction. However, the method that uses only hydrogel as the bioink base material exhibits limited biofunctional properties and needs improvement to achieve the desired tissue regeneration. In this study, we present a three-dimensionally printed bioactive microparticle-loaded scaffold for use in bone regeneration applications. The unique structure of the microparticles provided sustained release of growth factor for > 4 weeks without the use of toxic or harmful substances. Before and after printing, the optimal particle ratio in the bioink for cell viability demonstrated a survival rate of ≥ 85% over 7 days. Notably, osteogenic differentiation and mineralization-mediated by human periosteum-derived cells in scaffolds with bioactive microparticles-increased over a 2-week interval. Here, we present an alternative bioprinting strategy that uses the sustained release of bioactive microparticles to improve biofunctional properties in a manner that is acceptable for clinical bone regeneration applications.

A modular hydrogel bioink containing microsphere-embedded chondrocytes for 3D-printed multiscale composite scaffolds for cartilage repair

Articular cartilage tissue engineering is being considered an alternative treatment strategy for promoting cartilage damage repair. Herein, we proposed a modular hydrogel-based bioink containing microsphere-embedded chondrocytes for 3D printing multiscale scaffolds integrating the micro and macro environmentof the native articular cartilage. Gelatin methacryloyl (GelMA)/alginate microsphere was prepared by a microfluidic approach, and the chondrocytes embedded in the microspheres remained viable after being frozen and resuscitated. The modular hydrogel bioink could be printed via the gel-in-gel 3D bioprinting strategy for fabricating the multiscale hydrogel-based scaffolds. Meanwhile, the cells cultured in the scaffolds showed good proliferation and differentiation.Furthermore, we also found that the composite hydrogel was biocompatible invivo. These results indicated that the modular hydrogel-based bioinks containing microsphere-embedded chondrocytes for 3D printing multiscale scaffolds could provide a 3D multiscale environment for enhancing cartilage repairing, which would be encouraging considering the numerous alternative applicationsin articular cartilage tissue engineering.

Organoid bioprinting strategy and application in biomedicine: A review

Organoids are three-dimensional cell structures cultured in vitro. They are self-organizing and can mimic real organs in structure and function. Bioprinting technology breaks through some limitations of organoid manufacturing, making it more widely used in drug screening, regenerative medicine, and other fields. In this review, we first introduce bioinks and bioprinting methods for stem cell and organoid bioprinting, then summarize several vascularization strategies for bioprinting organoids, and present applications in biomedicine. In the future, the development of microfluidic technology and four-dimensional bioprinting technology may be conducive to forming better bioprinted organoids.