Our understanding of bioprinting originated from tissue engineering and 3D printing. Over the last two decades, 3D printing has been serving tissue engineering to fulfill its goal of solving the worldwide challenge of human organ shortage. Fundamental research and translation to clinical settings are currently the mainstream and have led to the emergence of translational bioprinting. However, as bioprinting evolves with more refined capabilities such as spatial and temporal controls of multiple biological materials at the microscale, perhaps it is time to reflect on a reciprocal approach, i.e., tissue engineering, to serve 3D printing with the hope to address problems more than or other than organ shortage. Recent examples of cultivated meat, digital bioprinting, bioelectronics, and space exploration may have just revealed the tip of the iceberg, though some still overlap with the goal of tissue engineering. Whenever a new material is introduced to the realm of 3D printing and becomes printable, it always leads to versatile or even unforeseen applications. This has happened to metals, ceramics, composite, and electronics. Although it has been known for a long time that biological cells are 3D-printable, the application of such concept has been always perceived from the angle of tissue engineering with human organ shortage as the sole motivation. Therefore, in this review based on existing evidence, we offer an innovative perspective of bioprinting, termed “transformative bioprinting,” to emphasize the role of an enabling tool of bioprinting and its alternative motivations.

The development of three-dimensional (3D) lung organs or tissues using gravitational methods and bioprinting technologies displays significant promise for producing lung tissue for research, pharmaceutical, and clinical applications. The advancement of innovative technologies can improve our understanding of lung diseases and, if necessary, enable the production of replacement lungs for transplantation. The development of functional organs-on-a-chip and disease-specific lung tissues could provide a deep understanding of the molecular mechanisms underlying lung diseases and aid the identification of drug targets. This knowledge has the potential to enhance our understanding of lung tissue regeneration processes, potentially leading to the development of more effective treatments for human lung diseases. This could eliminate the need for lung transplants in most disease-induced cases, as appropriate medications could induce regeneration of the damaged organ. This review highlights the importance of using a variety of materials, preparation methods, and sizes of lung tissues in 3D bioprinting technologies to better understand lung function, facilitate drug selection during therapy, and ultimately produce transplantable organs if needed. The review also emphasizes the need for improvements in legislation and guidelines for researchers aiming to achieve quality-assured biomanufacturing.

Hydrogels derived from the decellularized extracellular matrix (dECM) are widely used in three-dimensional (3D) bioprinting, mainly because they recapitulate the native tissue microenvironment and retain key growth factors and cytokines. Hence, they are characterized by adequate biocompatibility for use in 3D bioprinting. In liver tissue engineering, these materials, along with liver-derived cell types, can serve as appropriate in vitro hepatic models for drug efficiency testing and liver metabolism studies. These hydrogels can also be considered as good manufacturing practice-compliant systems for liver cell and organoid expansion, unlike routinely used basal membrane extract products derived from tumorigenic cell lines. Although weak mechanical properties and poor printability hinder the direct usage of dECM hydrogels as bioinks, various modifications of dECM and the bioprinting process are applied to overcome these problems. However, there are several complications regarding the scale-up and good laboratory practice-compliant manufacturing of these hydrogels: (i) the manufacturing standards for dECM hydrogels are not well established; (ii) the methods for obtaining these hydrogels are slightly varying, resulting in decreased reproducibility; and (iii) since these hydrogels are traditionally produced from animal tissue, the animal-to-animal variability, different harvesting conditions, and bioburden reduction need to be thoroughly considered. This review examines the essential properties of dECM hydrogels for biomedical applications, focusing on biocompatibility, mechanical strength, and bioactivity. Additionally, this review discusses production methods and modifications for 3D bioprinting, highlights case studies of dECM-based liver constructs, and addresses challenges in scalability and regulatory hurdles for clinical translation.

Methacrylic anhydride (MA)-based hydrogels, derived by introducing methacryloyl groups to various polymer side chains, are promising bioinks for three-dimensional (3D) printing in medical applications. These hydrogels combine the inherent biocompatibility and therapeutic benefits of their parent polymers with the unique photocrosslinking properties conferred by the methacryloyl groups, allowing precise control over their mechanical properties through light-curing parameters. Using 3D biological compression, these hydrogels serve as bioinks for producing scaffolds with optimal porosity, facilitating cell adhesion, proliferation, and differentiation. This technology enables the precise spatial distribution of bioactive substances, offering targeted therapeutic treatment and controlled release. This review delved into recent advancements in bioprinting technologies, outlined the preparation of MA-based bioinks, and summarized factors influencing the resulting biological and mechanical properties of bioscaffolds. Additionally, the properties and applications of methylpropionic anhydride-based hydrogels in various medical fields were discussed, addressing current limitations and future challenges in integrating these hydrogels with 3D bioprinting for clinical applications.

Researchers have developed smart shape-memory materials that adapt their structure or function to external stimuli. The demand for dynamic oral bone tissue repair is driven by continuous changes in bone and surrounding tissues during the repair process, such as tooth growth, movement, reconstruction of oral soft tissues, and skeletal differences in alveolar and craniofacial bones. These changes challenge the mechanical stability of bone implants and the precision of printing. Consequently, 4D printing technology introduces “time,” allowing pre-programmed changes in material shape or functionality, which enables scaffolds to respond to complex oral environments intelligently, achieving dynamic repair of bone and surrounding tissues. Despite its theoretical benefits in oral bone tissue engineering, the study and use of 4D printing technology is still in its infancy. This review explores the recent advances in 4D printing in dentistry, discussing skeletal structure, etiology of bone defects, and bone repair mechanisms. It also provides an overview of the materials, cells, and growth factors used in 4D printing bone tissue engineering. Thus, by reviewing existing studies, this review provides valuable insights for the future development of 4D printing technology in oral bone tissue engineering.

Diseases caused by bacterial infections, especially pathogen variations and drug-resistant bacteria, are a serious threat to human health globally. Accurate and rapid identification of bacterial pathogens is essential for early diagnosis of infections and timely treatment of disease. At present, the routine diagnostic methods for identifying bacterial pathogens in clinic are bacterial culture, immunological detection, genetic analysis, etc. These methods occupy foundational position for bacterial detection that favors for clinical diagnosis of pathogen infection in daily life. Notably, 3D printing technology, together with 3D bioprinting technology, provides more options for bacterial detection due to its personalized design and manufacturing. Compared with traditional methods, 3D printing provides a more convenient, rapid and accurate bacterial detection platform, thus meeting the urgent needs of clinical and scientific research. Here, we have summarized the research progress and given a comprehensive review of 3D printing technology in bacterial detection, including bacterial detection sensors, microfluidic chips, bioprinting microarray technology, AI and spectroscopy technology, providing a scientific reference and filling in gaps in 3D printing-assistance bacterial detection. At the same time, technical advantages, challenges and future development trends will also be discussed in related healthcare fields.

Musculoskeletal disorders, such as bone fractures, osteoarthritis, meniscus injuries, muscle diseases, and tendon injuries, are common disorders among individuals in need of rehabilitation. Trauma, sports-related injuries, and degeneration mainly cause these disorders. Regenerative rehabilitation medicine aims to enhance the regenerative capacity of musculoskeletal tissues and optimize functional recovery through the combination of regenerative medicine and rehabilitation medicine treatments. However, these treatments are insufficient for the complete restoration of damaged tissue structures. Three-dimensional (3D) printing technology, referred to as the additive manufacturing (AM) technique, can accelerate the rehabilitation process for musculoskeletal diseases, especially for developing regenerative rehabilitation and engineering rehabilitation. Recently, an increasing number of studies reported on the basic and clinical applications of 3D printing in assisting with the treatment of musculoskeletal disorders. Therefore, this review summarizes how 3D printing technologies are changing treatment and assessment methods, as well as improving therapeutic outcomes in regenerative rehabilitation for musculoskeletal diseases. Finally, this review discusses the current status of the clinical translation for 3D printing.

Osteoarthritis (OA) of the trapeziometacarpal joint (TMCJ) can be caused by biomechanical wear on the articular cartilage due to high joint contact pressure, leading to severe pain in the thumb. Static orthoses have been applied for treatment in the early stages of OA to immobilize the TMCJ in a comfortable posture, but they do not account for contact pressure at the TMCJ. This oversight results in a high failure rate in pain relief during splinting. To ensure successful treatment, it is desirable to immobilize the TMCJ in an optimal posture that minimizes biomechanical joint contact pressure. This paper presents a patient-specific TMCJ orthosis design for the optimal posture, based on joint contact pressure obtained from a computed tomography image-based finite element (FE) TMCJ model. The estimated pressure at the subject-specific optimal posture averaged 2.8E-3 MPa, which was lower compared to the average pressure of 3.2E-2 MPa at the non-optimal but comfortable posture. To maintain this subject-specific optimal TMCJ posture, the orthosis was designed based on individual hand geometries with three-dimensional (3D) printing technology. The 3D-printed orthosis was preliminarily evaluated by patients with moderate to severe OA, and all patients reported pain relief. The visual analog scale and disabilities of arm, shoulder, and hand scores improved by 1.8 ± 1.7 and 13.1 ± 5.4, respectively. For orthotic treatment in clinics, the FE model-based TMCJ orthosis design for the subject-specific optimal posture can relieve pain caused by OA.

Throughout a woman’s reproductive life, hundreds of functioning follicles are activated for development, while thousands of dormant follicles remain in the ovaries. In vitro dormant follicle activation is an effective clinical strategy for women with fertility needs facing ovarian dysfunction. However, in vivo dormant follicle activation remains a challenge due to difficulties such as delivering stimulators to local sites. Here, we developed a compound-preloaded microporous scaffold by combining three-dimensional (3D) printing techniques with pharmacological activators to support and stimulate the activation and development of primordial follicles. The gelatin/alginate composite scaffolds exhibited exceptional mechanical properties and biological compatibility, effectively supporting the survival of ovarian granulosa cells for more than 7 days, which is essential for oocyte development. Furthermore, the ovarian tissue scaffold complex successfully survived after transplantation under the mouse kidney capsule, demonstrating its excellent biocompatibility. After pre-mixing widely used clinical activators into the bioink, the scaffold could gradually release the mixture of compounds, effectively activating primordial follicles. By transplanting the ovary–scaffold complex containing activators into the mouse abdominal subcutaneous pocket, dormant follicles could be activated subcutaneously and developed into growing follicles. The number of growing follicles is approximately three times higher compared to the group without activators. In conclusion, by integrating biomaterials, activators, and 3D printing technology, we have developed 3D-printed biological scaffolds that can ectopically support primordial follicle activation and development in vivo. This novel approach could provide a promising strategy for treating ovarian insufficiency and endocrine disorders in the clinic, without the need for in situ ovarian tissue grafting.

Following dental extraction, the alveolar bone and gingival tissues could undergo varying degrees of resorption, which affects subsequent implant integration and aesthetic outcomes. Thus, having adequate volume of both hard and soft tissues for implantation or aesthetic restoration is essential for optimal results. Three-dimensional (3D) bioprinting technology offers the advantages of biomimicry, personalization, and precise spatial distribution, which are pivotal for enhancing the success and esthetics of dental restorations. In this study, we fabricated a construct with a natural transition and varying material concentrations by 3D bioprinting, comprising an upper layer of collagen/alginate/periodontal ligament stem cells (PDLSCs) and a lower layer of collagen/nano-hydroxyapatite (nHA)/alginate/PDLSCs. Characterization of the physicochemical properties revealed that the incorporation of nHA significantly enhanced the mechanical properties of both the bioink and the construct.Flow cytometry analysis confirmed the stemness of PDLSCs. Scanning electron microscopy (SEM) revealed that the construct possesses satisfactory pore density and a natural transition at the stratification point. The construct displayed good cell viability and proliferation, with the cellular movement observed at the stratification interface after bioprinting. Differentiation staining and quantitative reverse-transcription polymerase chain reaction (RT-qPCR) results demonstrated that PDLSCs within the 3D construct are capable of both osteogenic and fibroblastic differentiations. Ectopic transplantation in mice confirmed the biocompatibility of the construct. A rat tooth extraction model validated the construct’s effectiveness in the integrated regeneration of both hard and soft tissues in alveolar ridge preservation. In conclusion, this personalized, concentration-varied 3D construct exhibits excellent biocompatibility and tissue preservation effects, holding significant potential for clinical application.

3D bioprinting is a focused field in orthopedics, and its application with physiological osteogenic microenvironments (POMEs) is a prerequisite for authentic bone reconstruction. Mechanical stimulation produces prostaglandin E2 (PGE2) in mechanosensory osteocytes, but it remains unclear whether osteocytic PGE2 is a POME. PGE2 is an inducer of osteogenesis by acting on bone marrow stromal cells through its receptors EP2/EP4 to initiate osteogenic differentiation and mineralization. Unfortunately, clinical trials of PGE2 have reported side effects, including fever and drowsiness; targeting the PGE2 receptor in specific tissues can avoid these side effects. Here, we demonstrate that osteocytic cell line MLO-Y4 from murine long bones treated with EP2/EP4 agonists for 24 h enhance osteogenic differentiation and mineralization, inhibit adipogenesis of the stromal cell line ST2, and induce tubule formation and angiogenic marker expression in human umbilical vein endothelial cells (HUVECs). Mechanistically, activation of the PGE2 signaling pathway in osteocytes induces autocrine effects by upregulating the expression of EP2/EP4 receptors and COX-2 (Ptgs2), further amplifying PGE2 signaling. PGE2 produced by treated MLO-Y4 cells appears responsible for osteogenesis, alongside other unidentified factors. MLO-Y4 and ST2 cells, incorporated into POME 3D constructs, maintained over 95% viability over seven days. Treatment of osteocytes with a PGE2 receptor agonist promotes ST2 cell proliferation and enhances osteoblast marker expression and mineralization. As 3D bioprinting closely models in vivo conditions, these data suggest that osteocytic PGE2 receptor signaling is a safe and mild POME with great potential for translational applications.

Artificial temporomandibular joint (TMJ) replacement is a common intervention for the treatment of advanced TMJ diseases and ankylosis. The present study addresses the insufficient elasticity of existing artificial TMJs through the development of a composite material by incorporating high-density polyethylene into ultra-high-molecular-weight polyethylene. This was processed using fused deposition modeling 3D-printing technology to produce porous elastic layers with an elastic modulus similar to that of joint discs. An artificial TMJ prosthesis with physiological elasticity was successfully fabricated, applied to the surface of porous Ti–6Al–4V alloy, and validated through mechanical experiments. The results demonstrated that the elastic modulus of the synthetic cartilage exhibits a negative correlation with the number of staggered layers, while no significant relationship was observed between the elastic modulus and the alternating angle between the harnesses. The elastic modulus of the cartilage was measured to be 127.5 ± 16.1 MPa, while the maximum compressive strength was found to be 8.0 ± 1.3 MPa. Optimal performance was observed for a staggered layer count of five and a cross-angle of 90°. The bonding strength to the metal mandibular prosthesis was measured to be 2.62 ± 0.98 MPa, and the surface roughness was determined to be 1.6 μm. An elastic artificial TMJ process prosthesis in this study was successfully designed, fabricated, and validated through in vitro experiments, offering valuable insights for future advancements in artificial TMJ design.

Segmental tracheal reconstruction remains a significant clinical challenge due to the lack of ideal tracheal substitutes. Three-dimensional (3D) bioprinting technique offers a promising avenue for the development of native-like tracheal substitutes. However, several challenges remain to be addressed, including deformation of 3D-printed C-shaped cell-laden hydrogels, fusion of regenerated C-shaped cartilage, and difficulty in regenerating vascularized connective tissue. Herein, we utilized 3D printing techniques to fabricate C-shaped chondrocyte-laden GelMA/ PCL (CcGP) and S-shaped PCL chains (SPC). These were assembled into the SPC-CcGP construct, followed by mold casting (VEGF@GelMA) to establish tissue-engineered tracheal construct (TETC). In vitro experiments confirmed the stable chondrogenic potential of CcGP and the angiogenic capability of VEGF@GelMA. Subcutaneous implantation in nude mice and orthotopic transplantation in rabbit model further demonstrated that the TETC could achieve stable regeneration of cartilage and vascularized connective tissue. The engineered trachea could maintain luminal patency following prompt repair of rabbit tracheal defects. This study offers a promising approach for developing engineered tracheas with regenerated cartilage and vascularized connective tissue for prompt and effective segmental tracheal defect repair.

Biofabrication of cardiac patches is a challenging strategy proposed as an alternative to transplantation for end-stage heart failure patients. The optimization of the bioink used for this strategy can be limited by costs, properties, and biocompatibility of its building blocks. Lately, sericin has emerged within a wide range of natural proteins, thanks to its bioadhesive and biocompatibility potential. In this study, we assessed for the first time the effects of adding silk sericin on alginate-gelatin hydrogels, proposed for cardiac applications. To this aim, we first biofabricated sericin-containing hydrogels with increasing protein concentrations. Thus, we characterized hydrogels’ mechanical behavior, porosity and structure through rheology, Brillouin microspectroscopy, and scanning electron microscopy. Then, we bioprinted the formulated hydrogels and evaluated their effects on human cardiac spheroids (CSs) in vitro. Our mechanical characterization demonstrated that adding sericin significantly enhanced the elasticity and the viscosity of alginate-gelatin hydrogels. Sericin also modified hydrogels’ swelling behavior and their pore size, increasing by 20%, 62%, and 92% in Ser1%, Ser2%, and Ser3%, respectively. Although Ser1% did not exhibit significant effects on CSs, Ser2% and Ser3% enhanced cardiac cell viability for up to 14 days compared to the sericin-free hydrogel by acting on the fibroblast population. Sericin-based bioinks showed better printability and durability with +33% and +28% intact patches after 28 days of culture at 37°C compared to alginate-gelatin. Taken together, our results validated the use of sericin as a promising component for the optimization of bioink intended for cardiac applications.

Surgical interventions of the rotator cuff (RC) tendons are failing at unacceptably high rates. This is primarily due to clinical strategies failing to regenerate the biomechanical junction between bone and tendon (enthesis). Tissue engineering approaches for RC repair involve attempts at increasing the acute strength of the repair and directing the healing cascade to regenerate the enthesis. Advances in bioprinting, specifically melt electrowriting (MEW), allow precise fabrication of microarchitectures. Our group has utilized the functionality MEW offers to create a novel, single-material, gradient scaffold that approaches the mechanical gradients present in the RC. To characterize this novel geometry, high-throughput, parametric finite element analysis (FEA) models were generated: (1) to determine how tunable print parameters such as the radius of curvature of fibers, the fiber diameter, and the fiber spacing alter the gradient present in the scaffold’s architecture; and (2) to predict, at the cellular level, what strain the scaffold generates regionally to instruct’’ the local cell milieu to produce healthy tissues (e.g., bone and tendon). FEA models predicted that mechanical gradients in the scaffold approached gradient levels seen in the RC (≈2 orders of magnitude), in which global strain gradients were driven by the radius of curvature of fibers. Additionally, our novel architecture significantly affected regional mechanics, which could be optimized for tenocyte and osteoblastic bioactivity. The data presented demonstrate a novel, tunable architecture capable of approaching biologically relevant gradients observed in the RC with potential to address the clinical problems associated with tendon–bone repairs in other regions of the body using only a single material.

Combining the technologies of 3D bioprinting and human induced pluripotent stem cells (hiPSCs) has allowed for the creation of tissues with organ-level function in the lab, a promising technique for disease modeling and regenerative medicine. Expanding the stem cells in bioprinted tissues prior to differentiation allows for high cell density, which is important for the formation of cell-cell junctions necessary for macroscale function upon differentiation. Yet, stem cell expansion, critical to successful in situ differentiation, depends heavily on the composition of the bioprinted scaffold. Here, we demonstrate how a common bioink component, gelatin methacryloyl (GelMA), varies depending on the vendor and degree of functionalization. We found that the vendor/GelMA production technique played a greater role in dictating the mechanical properties of the bioprinted constructs than the degree of functionalization, emphasizing the importance of reporting detailed characterization of GelMA scaffolds. Furthermore, the ability of singularized hiPSCs to survive and expand in GelMA scaffolds greatly varied across batches from different vendors and degrees of functionalization, where expansion correlated with the mechanical properties of the scaffold. Yet, we found that using a commercial cloning supplement could restore the ability of single hiPSCs to survive and expand across GelMA types, thus compensating for the varied mechanical properties of the scaffolds. T hese fi ndings provide a pr actical guide fo r the ex pansion of hiPSCs in GelMA constructs with various mechanical properties as required for successful in situ differentiation.

Parkinson’s disease (PD), a common neurodegenerative disorder, is characterized by dopaminergic (DA) neuron apoptosis, mitochondrial dysfunction, and aggregation of α-synuclein (α-syn). In this study, we developed a three-dimensional (3D)-bioprinted neuroinflammatory co-culture model to simulate key pathological features of PD in vitro. Traditional 2D cell culture models fail to accurately replicate the complex microenvironment of PD, leading to the development of the 3D-bioprinted model. Utilizing a polyethylene glycol-hyaluronic acid methacryloyl hydrogel matrix, this model supports the co-culture of DA neurons and microglia, enabling a more accurate representation of PD pathology. Experimental results demonstrated that, under 6-hydroxydopamine induction, the 3D model successfully mimicked neuroinflammatory responses associated with PD, including M1 polarization of microglia and increased secretion of pro-inflammatory factors. Compared to traditional 2D models, DA neurons in the 3D model exhibited greater resistance to oxidative stress and neurotoxic challenges, with significantly slower rates of apoptosis. Additionally, the 3D model displayed key PD-specific pathological features, such as altered mitochondrial membrane potential, elevated reactive oxygen species levels, and overexpression of α-syn. This 3D-bioprinted PD model provides a closer-to-physiological platform for investigating the pathogenesis of PD and holds potential for use in drug screening. However, further optimization is required to enhance the model’s complexity and long-term stability, including incorporating peripheral immune cells to better simulate the progression of chronic neuroinflammation.

Bone tissue engineering requires scaffolds with three-dimensional (3D) structures that facilitate vascularization and new tissue growth. 3D printing, especially through fused deposition modeling (FDM), has emerged as an effective method for creating complex structures with high reproducibility. Early research in this area demonstrated the potential of poly(ε-caprolactone) (PCL) and poly(L-lactide) (PLLA) scaffolds for bone regeneration. Recently, polylactide (PLA) and polyhydroxyalkanoates (PHAs) have garnered attention for their biocompatibility and ability to support cell proliferation. Among PHAs, poly(3-hydroxybutyrate) (PHB) shows promise due to its intrinsic biocompatibility and resorbability, making it a candidate for FDM-based scaffold fabrication. In the presented study, we aim to develop and optimize a biocompatible PHB-based composite material for bone tissue engineering, incorporating PLA, hydroxyapatite, and the plasticizer Syncroflex 3114 to enhance mechanical properties and printability. This composite was processed into filaments for 3D printing and characterized through thermal, mechanical, and biological evaluations. Using a design of experiment approach, we investigated factors such as temperature performance, warping, degradation, and strength to determine the optimal composition for use in tissue engineering. Four optimal mixture compositions fulfilling the optimization criteria of having the most suitable properties for bone tissue engineering, namely the best printability and maximum mechanical properties, were obtained. The mixtures were optimized specifically for minimum warping coefficient (0.5); maximum flexural strength (66.9 MPa); maximum compression modulus (2.4 GPa); and maximum compression modulus (2.3 GPa) with a warping coefficient of no more than 1 at the same time. In conclusion, the study shows a new possible way to effectively develop and test 3D-printed PHB-based scaffolds with specifically optimized material properties.

Polycaprolactone (PCL) is one of the most widely used three-dimensional (3D) printing materials with excellent biocompatibility and mechanical properties. However, its hydrophobic nature hinders cell adhesion and proliferation. Polydopamine (PDA) has been shown to promote proliferation and induce osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) on polymer surfaces. Despite this, the impact of varying PDA coating thicknesses on the osteogenic differentiation of BMSCs has been minimally explored. In this paper, PCL scaffolds were fabricated using 3D printing technology, and PDA-coated PCL scaffolds (PDA-PCL-0, PDA-PCL-3, PDA-PCL-6, PDA-PCL-24) were prepared by immersing the scaffolds in an aqueous dopamine solution for fixed time points (0, 3, 6, 24 h) under constant shaking. The scaffolds were characterized and subjected to physicochemical performance tests to evaluate their effects on BMSC proliferation, adhesion, and osteogenic differentiation. The results showed that PDA-PCL-6 scaffolds exhibited significant immunomodulatory properties, promoting BMSC proliferation, adhesion, and osteogenic differentiation more effectively than the other groups. In vivo validation experiments, including micro-computed tomography, hematoxylin and eosin staining, Masson staining, and immunohistochemical analysis of bone morphologenetic protein 2 (BMP-2) and type I collagen (COL-I), confirmed that PDA-PCL-6 scaffolds significantly enhanced bone regeneration, histocompatibility, and hemocompatibility compared to uncoated scaffolds at 1, 2, and 3 months postoperation. In conclusion, our results indicate that a PDA coating obtained through 6-h immersion significantly enhances the biocompatibility and osteoinductive properties of PCL scaffolds, providing a promising strategy for bone defect repair.

Dermal substitutes (DS) have been widely used in wound repair, but the low-survival rate of skin grafts with a DS remains an important challenge in regenerative medicine. This study aims to investigate the efficacy of combining prevascularized human mesenchymal stem cell sheets (PHCS) with DS in improving full-thickness wound healing. We used porcine dermis-derived decellularized extracellular matrix to construct an optimized 3D-printed DS, which exhibited the desired structure, good mechanical properties, and biocompatibility. Meanwhile, we constructed PHCS with a certain microstructure, which could enhance microvessel formation and maturation and upregulate the expression of angiogenic growth factors. An immunocompetent one-stage skin graft model in vivo demonstrated that the combination of PHCS and DS, along with split-thickness meshed skin autografting, could improve the repair effect of skin grafts, reduce graft fibrosis and later scar formation, and increase blood perfusion of skin grafts through early angiogenesis and rapid microvessel maturation. Our results suggest that the combination of PHCS and DS improves the repair effect of skin grafts through early angiogenesis for full-thickness skin defect repair.

Cartilage defects negatively impact the quality of life of over 500 million people worldwide. 3D-printed scaffolds loaded with polydatin (PD) have shown significant potential in cartilage defect repair. This study aims to investigate their reparative effects and analyze the associated metabolic changes using lipidomics techniques, providing new strategies for treating cartilage defects. Biocompatible 3D-printed scaffolds containing PD were prepared and 30 New Zealand rabbits were divided into three groups (10 rabbits per group) that underwent either sham surgery (Normal group) or surgical creation of a cartilage defect without scaffold filling (Model group) or with the developed scaffold filling (Scaffold group). After three months of intervention, the repair of cartilage defects was evaluated through macroscopic observation, micro-CT, hematoxylin and eosin (H&E) staining, and Safranin O/fast green (SFO/FG) staining. The expression of vascular endothelial growth factor A vascular endothelial growth factor A (VEGFA), Col2a1, and biglycan was detected by immunofluorescence while lipid metabolic profiling analysis was conducted on newly formed cartilage tissue to comprehensively evaluate the scaffold’s mechanism of action. Macroscopic observation, micro-CT, H&E staining, and SFO/FG staining indicated that the repair of cartilage defects in the Scaffold group was significantly better than in the Model group, closely resembling the Normal group. Lipidomics revealed that the Scaffold group modulated 36 metabolites, with a recovery rate of 69.23%, including ceramides (Cers), glycerophospholipids (GPs), and sphingomyelins (SMs). Immunofluorescence analysis showed increased expression of cartilage cell markers Sox9, Col2a1, biglycan, and VEGFA, along with a reduction in cell apoptosis (all p <0.05) after scaffold implantation. These findings collectively suggest that the PD-loaded 3D-printed scaffold promotes cartilage repair by restoring lipid metabolites in cartilage tissue, inhibiting chondrocyte apoptosis, enhancing vascular-related protein expression, and accelerating cartilage collagen matrix remodeling.

The intervertebral disc, a fibro-cartilaginous structure, contains a gelatinous core (nucleus pulposus) surrounded by collagen fiber lamellae (annulus fibrosus). Intervertebral disc degeneration leads to a debilitating disorder, and new treatments are currently being developed. Unfortunately, conventional monolayer in vitro models fail to predict the clinical efficacy of novel therapies accurately. Here, we report a bioprinted construct that mimics the macroscopic and microscopic architecture of the intervertebral disc. First, a 3D model was created from a histological section of a sheep lumbar intervertebral disc. The printability of the ink, gelatin (7% w/v), alginate (0.6% w/v), and hyaluronic acid (0.2% w/v) was optimized by varying the printing pressure (70–110 kPa), printing speed (2–10 mm/s), and nozzle type (needle or tip). Nucleus pulposus and annulus fibrosus cells, harvested from 4-month-old lambs, were bioprinted (5 × 105 cells/mL) using an in-house extrusion bioprinter. Cell viability (live/ dead assay), shape (actin immunostaining), distribution (confocal microscopy), and matrix synthesis (immunostaining) were evaluated after 21 days of culture. We used a parametric study to quantify and optimize the factors (pressure, printing speed, nozzle type) influencing the filament width. The 3D construct exhibited fidelity to the initial design and maintained stability in length, width, and height for 21 days. Fluorescent labeling confirmed the distribution of nucleus pulposus and annulus fibrosus cells in each tissue, replicating the native intervertebral disc structure. We also evidenced cell viability and collagen type 1 synthesis. This bioprinted construct offers a promising alternative to current in vitro models, potentially enabling more relevant preclinical evaluations.

The excessive use of antibiotics has precipitated the emergence of drug-resistant bacterial strains, underscoring the critical need for developing novel, targeted antimicrobial agents. Among the burgeoning class of nanomaterials, silver clusters have attracted considerable attention due to their broad-spectrum and enduring antimicrobial properties, coupled with the crucial advantage of not eliciting resistance. These features render them exceptionally promising in the landscape of antimicrobial therapy. Nevertheless, the constraints associated with the topical application of silver clusters and the adverse effects linked to high-dose shock therapy pose significant challenges that require resolution. To surmount these obstacles, we engineered a sophisticated nanodrug delivery system capable of specific bacterial recognition and synergistic interaction with antimicrobial agents to accomplish precise antibacterial efficacy. Through the interaction between bacterial recognition receptor proteins (TLR2 and TLR4) on macrophage membranes and pathogen-specific molecular patterns on bacteria, we observed that cultivating macrophages in the presence of specific bacteria markedly upregulated the expression of these receptors. We subsequently isolated these specialized membrane proteins, integrated them into liposomes, and loaded silver clusters to formulate composite biomimetic liposomes (Lip@MOMP2@AgNCs). These liposomes can be effectively administered to sites of vaginal infection via intravenous injection, facilitating specific bacterial recognition, and precise targeting. Moreover, we devised a 3D-printed hydrogel mesh scaffold incorporating Lip@MOMP2@AgNCs, which amalgamates the injectable liposomal formulation with the 3D-printed hydrogel scaffold to realize sustained and localized drug release. This investigation not only advances a specific and promising therapeutic strategy for combating drug-resistant Candida albicans vaginitis but also forges new pathways in addressing the formidable challenge of antibiotic resistance.

Tendon-to-bone interface (TBI) injuries have become increasingly common due to the growing competition in sports. Electrohydrodynamic (EHD) three-dimensional (3D) printing is a promising strategy for controllably fabricating biomimetic micro/ nanoscale architecture in musculoskeletal tissue engineering. This study aims to fabricate a novel biomimetic EHD-printed poly(ε-caprolactone) (PCL) with gradient hydroxyapatite (HA) nanoparticles utilizing modified dopamine self-polymerization reaction and assess the biocompatibility and efficacy of osteogenic differentiation and interface regeneration in vivo. The fabricated scaffold PCL-PDA-HA (PPH) has a diameter of 190.35 ± 41.96 nm in areas with lower HA concentration and 446.54 ± 125.42 nm in areas with higher HA concentration; the scaffold was demonstrated to profoundly facilitate osteogenic differentiation of tendon stem/progenitor cells (TSPCs), enhancing the expression of RUNX2 and ALP. On day 14, the expression of osteogenic genes, including Bmp2 (~3.12-fold, p < 0.001) and Runx2 (~3.24- fold, p < 0.001), was significantly elevated compared to those of PCL groups. New fibrocartilage formation and TBI healing were observed in the PPH group in vivo. Therefore, our work demonstrated a facile green synthesis avenue for enhancing TBI healing via TSPCs’ osteogenic differentiation, which supplied a novel approach to augment the therapeutic effects of ligament graft in TBI reconstruction.

Spinal fusion surgery is an effective therapy for patients with disc herniation and degenerative disc disease. In this procedure, the intervertebral cage plays a key role in reconstructing stability and achieving fusion, though its clinical efficacy is limited by inadequate osseointegration. In this study, we developed a tantalum (Ta) cage, featuring micro-scale roughness and a porous microstructure, using advanced three-dimensional (3D) printing techniques. The aim of the study was to investigate its osteogenic potential in vitro and intervertebral fusion capability in vivo. Compared with conventional polyetheretherketone cages, in vitro biological experiments demonstrated that the 3D-printed porous Ta (3D-pTa) cages significantly enhanced osteoblast adhesion, proliferation, and differentiation. In vivo spinal fusion studies in a sheep model demonstrated significant increases in bone-implant contact and bone volume to total volume ratios (p < 0.05) with the 3D-pTa cages, indicating marked bone ingrowth and effective spinal fusion. Additionally, mechanical tests revealed that the 3D-pTa cages provided consistent stability and stiffness, significantly reducing the range of motion at various time points (p < 0.05). Our findings indicate that the 3D-pTa cage effectively facilitates bone fusion and possesses reliable biosafety, highlighting its potential for future clinical application in spinal surgery.

Constructing a cell-inductive scaffold that promotes the proliferation of cardiac-specific host cells for effective myocardium repair is a great challenge in the realm of cardiac tissue engineering. Three-dimensional (3D) printing allows for the precise fabrication of intricate structures like cardiac patches but produces large pores (sub-macron), reducing surface area for cell attachment and tissue regeneration. Moreover, the hydrophobic nature of most polyesters used in 3D printing further complicates cell adhesion and integration. In this study, human chorion placenta extracellular matrix (hpcECM) hydrogel with highly preserved ECM components, such as glycosaminoglycans (GAG), elastin, and collagen, was coated on a hydrophobic 3D-printed poly-ε-caprolactone (PCL) patch. The presence of hpcECM on the 3D-printed PCL patches could significantly induce higher levels of cell attachment, proliferation, and activation of cells such as human umbilical vein endothelial cells (HUVECs), endothelial progenitor cells (EPCs), H9c2 undifferentiated/differentiated cardiomyoblasts and fibroblasts. Fibronectin-coated samples served as controls in the experiment. Coating efficiency, hpcECM modulus of elasticity (in nanoscale), surface profile roughness, and contact angle measurements were performed and confirmed the significant potential of hpcECM as a stable, soft, hydrophilic coating matrix with low modulus of elasticity for 3D-printed synthetic constructs. Furthermore, hpcECM could modulate the high expression of inflammatory genes (CCR7 and IL-1α, expressed after 72 hours) via high expression of IL-10 in macrophages after one week. Expression of adhesion molecules (ICAM, VCAM-1, and PECAM-1) and hemolysis rate did not show statistically significant changes. All these findings highlight hpcECM as a promising immunomodulatory matrix supporting tissue-specific cell attachment and activation; particularly, hydrophobic 3D-printed constructs would outperform equivalents like fibronectin-coated constructs.

Meniscal injuries are a leading cause of knee dysfunction and are commonly treated with partial meniscectomy, which often leads to altered joint biomechanics and early onset osteoarthritis. Current meniscal implants and scaffolds fail to address patient-specific anatomical variations, particularly for partial defects, limiting their clinical effectiveness. This pioneering study introduces the first methodology specifically designed to develop patient-specific scaffolds tailored to partial meniscal injuries, representing a groundbreaking advancement in the field. By using medical imaging and computer-aided design, precise 3D models of injured and intact menisci were created, leveraging the contralateral meniscus as a reference. Scaffolds were fabricated through extrusion-based 3D printing to enable accurate replication of the defect geometry. Ex vivo analyses demonstrated the scaffolds’ adaptability to diverse defect types and their morphological fidelity to the native tissue. Quantitative assessments revealed minimal deviations, underscoring the precision of the proposed method. This innovative methodology provides a robust framework for developing anatomically precise scaffolds, paving the way for personalized regenerative strategies. Beyond its current application, this method holds potential for creating cell-laden scaffolds, acellular implants, or permanent prosthetic devices, addressing critical challenges in meniscal repair and advancing patient-specific tissue engineering.

This study presents a pioneering approach utilizing hierarchically functionalized scaffolds to foster anisotropic osteochondral tissue regeneration, leveraging the integration of distinct yet interconnected layers. We developed 3D-printed polydopamine-modified polycaprolactone (PCL) scaffolds, which were subsequently covered with a layer of electrospun PCL-gelatin fibers, and then functionalized with gelatin-bone morphogenetic protein-2 (BMP-2) following oxygen plasma surface treatments, creating a hierarchically organized multi-phasic architecture. This interconnected porous microstructure enabled controllable degradation while maintaining mechanical integrity and hydroxyapatite mineralization. In vitro assessments demonstrated that the scaffolds provided superior support for rat bone marrow mesenchymal stem cells, marked by their enhanced adhesion, viability, and proliferation. Increased alkaline phosphatase activity and osteocalcin expression over 14 days indicated that the scaffolds enhanced osteogenic performance, likely due to BMP-2 interaction with serum proteins, as supported by simulation studies, augmenting growth factor bioavailability. In vivo investigations in rabbit critical- sized osteochondral defects at 4- and 12-week post-implantation demonstrated that the multi-phasic scaffolds notably promoted secretion of type I and II collagen, neo-tissue formation, and integration with surrounding tissue, with significant results observed at 12 weeks. These findings indicate the potential of multi-phasic scaffolds for osteochondral tissue regeneration.

The global shortage of donor eye bank tissue has significantly impeded advancements in biomaterial for corneal implantation. To address this issue, we have developed a three-dimensional (3D)-printed artificial cornea using a composite scaffolds of sodium alginate (SA) and cellulose nanofibers (CNF), crosslinked with poly-L-lysine-co-L-glutamic acid (PLL80GA20, PG) and calcium chloride (CaCl2, CC). The 2 wt% SA/ CNF composite scaffolds offer several advantages, including low toxicity, cost-effectiveness, excellent printability, and high mechanical strength, even with low crosslinker concentrations. The PG was synthesized via ring-opening polymerization of L-glutamate N-carboxyl anhydride (BGNCA) and L-lysine N-carboxyl anhydride (CBZNCA). The purity of the monomers was verified through differential scanning calorimetry analysis, revealing a melting point of 97°C. The molecular weight of the synthesized PG was determined to be 47 kDa. A dual crosslinking strategy was employed, starting with electrostatic crosslinking, followed by ionic crosslinking using varying concentrations of PG and CC at different effective charge concentrations of 6.25 12.25, and 25 mM.The hydrogel and 3D-printed cornea were comprehensively evaluated for chemical structure, surface functional groups, water content, mechanical strength, orientation, cytotoxicity, biocompatibility, and transparency. Notably, the inclusion of PG significantly enhanced the mechanical properties of the 3D-printed cornea, with the hydrogel achieving a storage modulus of 2,360 kPa at 6.25 mM of PG/CC, while maintaining over 95% water content. The artificial cornea demonstrated 86% transparency, and the cell viability showed 96% viable on day 7 with degradation rate of 35.9% in 28 days. The superior hydrophilicity, transparency, and mechanical strength of the printed scaffolds highlights their potential for the development of full-thickness corneal structures, making them a promising candidate for future corneal implants.

Tissue-engineered trachea offers a potential solution for patients needing long-segment tracheal resections. In our research, robust neotissue growth, including cartilage, muscle, adipose, and glands, was observed on the external surface of three-dimensional (3D)-printed tracheal grafts transplanted into a 3-month-old large-scale porcine, noticeable after 7 days. This study is the first to categorize the regeneration stages in detail, aiming for a clearer understanding of the cell development process, as previous studies have not fully elucidated the mechanisms of chondrogenesis and glandogenesis. We have identified four stages of chondrogenesis based on chondrocyte numbers, protein expression, and perichondrium presence. Muscle cells evolved from a fibroblast-like state, confirmed by alpha-smooth muscle actin and smooth muscle-myosin heavy chain markers, while initial adipose tissue resembling brown fat diminished over time. Gland development, marked by a change in MUC5B expression, paralleled the findings in native trachea epithelium and submucosal glands. Transforming growth factor-β1 and type XII collagen were key indicators in the emerging neotissue post-transplant.