Stereolithography apparatus and digital light processing-based 3D bioprinting for tissue fabrication

Fabrication of 3D Printed Microneedle Patch for the Simultaneous Delivery and Detection of Melatonin from Interstitial Fluid

Interstitial fluid (ISF) offers a potential alternative to invasive blood sample collection for biomolecule analysis. Microneedle (MN) patch application can collect ISF in a minimally invasive manner. Polyethylene glycol diacrylate MN patch was fabricated using optimized masked stereolithography-based 3D printing technique. Different 3D printing parameters including ink formula, exposure time, layer thickness, lift speed and distance, printing angle were optimized to fabricate pyramidal MN array. MN patch was characterized for design features, mechanical strength, in vitro, ex vivo and in vivo aspiration of fluid. MN patch aspirated 15 ± 2 µl ISF after application for 10 min in the rat model. Circadian rhythm controlling melatonin hormone was analyzed from ISF. The melatonin concentration ranged from 81 ± 13 to 178 ± 11 pg/ml and 94 ± 20 to 202 ± 6 pg/ml in ISF and serum from light to dark cycle, respectively. Furthermore, two different concentrations of melatonin were loaded in the MN patch during the 3D printing process. The two patches, blank MN patch for collection of ISF for melatonin detection (melatonin aspiration patch) and melatonin loaded patch for delivery (melatonin delivery patch) were simultaneously applied on the rat. Melatonin concentration increased by 4.6 and sixfold in ISF and serum, respectively after application of 20 µg melatonin MN patch, which was determined by blank MN patch application. Taken together, mSLA 3D printing technique can be used to fabricate melatonin loaded MN patch to deliver and collect ISF for melatonin analysis.

Imaging-Guided Microscale Photothermal Stereolithography Bioprinting

Stereolithography bioprinting relies heavily on costly photoinitiators for polymerization, limiting its potential for further technical advancement to meet growing needs in tissue engineering and regenerative medicine. Thermal initiators, in contrast, are low cost, and rapid growth of the photothermal conversion field offers a wide range of materials and tools to convert light into heat. However, high-resolution photothermal stereolithography bioprinting remains unattainable due to the difficulty of confining heat in an aqueous environment. Here, this challenge has been fully addressed by establishing imaging-guided microscale photothermal stereolithography bioprinting (ImPSB). This technique is achieved through building a novel imaging-guided stereolithography system that provides depth-resolved visualization of the printing dynamics, creating a unique photothermal initiator in the second near-infrared window, and developing a new bioink by seeing and controlling the photothermal gelation process. ImPSB achieves a printing resolution of ≈47 µm and generates smooth lines of arbitrarily designed shapes with a cross-sectional diameter as small as ≈104 µm, representing an unprecedented scale from photothermal aqueous stereolithography. Its cellular biocompatibility in printing both bioscaffold and cell-laden hydrogel is demonstrated, and its feasibility of transdermal printing is also shown. This work sets a new path for high-resolution stereolithography bioprinting where the vast photothermal resources can be utilized.

Effects of fused deposition modeling (FDM) printing parameters on quality aspects of polycaprolactone (PCL) for coronary stent applications: A review

Fused deposition modeling (FDM) is emerging as a promising technique for manufacturing bioresorbable stents (BRS), particularly for coronary artery disease treatment. Polycaprolactone (PCL) has emerged as a favored material due to its biocompatibility, controlled degradation rate and mechanical properties. This review provides a comprehensive analysis of the effects of key FDM printing parameters on the quality aspects of PCL-based BRS, focusing on morphological, mechanical and biological characteristics. This review also highlights inconsistencies in previous studies, particularly in the impact of these parameters on stent dimensions and mechanical properties, emphasizing the need for standardization in experimental methodologies. Additionally, the current gaps in research related to the mechanical and biological performances of PCL-based BRS are discussed, with a call for further studies on long-term effects. This review aims to guide future research by offering insights into optimizing FDM parameters for improving the overall performance and clinical outcomes of PCL-based BRS.

Digital Light Processing 3D Printing Technology in Biomedical Engineering: A Review

As one of the 3D printing technologies, digital light processing (DLP) 3D printing technology has been widely applied in biomedical engineering. The principles and advantages of DLP 3D printing technology are compared with other 3D printing technologies, while the characteristics and applicable fields of each technique are analyzed. The applications of DLP 3D printing technology in tissue engineering, medical devices and pharmaceutical field are classified and summarized. Besides, the prospects and challenges of DLP 3D printing technology in biomedical engineering are discussed. With continuous advancement, DLP 3D printing technology will play an increasingly important role in personalized medicine and regenerative medicine.

3D bioprinting technology innovation in female reproductive system

Several diseases affect the female reproductive system, and both disease factors and treatments impact its integrity and function. Consequently, understanding the mechanisms of disease occurrence and exploring treatment methods are key research focuses in obstetrics and gynecology. However, constructing accurate disease models requires a microenvironment closely resembling the human body, and current animal models and 2D in vitro cell models fall short in this regard. Thus, innovative in vitro female reproductive system models are urgently needed. Additionally, female reproductive system diseases often cause tissue loss, yet effective tissue repair and regeneration have long been a bottleneck in the medical field. 3D bioprinting offers a solution by enabling the construction of implants with tissue repair and regeneration capabilities, promoting cell adhesion, extension, and proliferation. This helps maintain the long-term efficacy of bioactive implants and achieves both structural and functional repair of the reproductive system. By combining live cells with biomaterials, 3D bioprinting can create in vitro 3D biomimetic cellular models, facilitating in-depth studies of cell-cell and cell-extracellular microenvironment interactions, which enhances our understanding of reproductive system diseases and supports disease-specific drug screening. This article reviews 3D bioprinting methods and materials applicable to the female reproductive system, discussing their advantages and limitations to aid in selecting optimal 3D bioprinting strategies. We also summarize and critically evaluate recent advancements in 3D bioprinting applications for tissue regeneration and in vitro disease models and address the prospects and challenges for translating 3D bioprinting technology into clinical applications within the female reproductive system.

Agarose Hydrogels for Bone Tissue Engineering, from Injectables to Bioprinting

A great interest in agarose, with many health-promoting and gel properties, has been registered, especially in the field of bone regeneration and repair. Agarose and its major bioactive compounds are involved in biological activities such as inflammation, cell adhesion and proliferation, and the promotion of tissue repair. Due to its unique physical properties like gelation and solubility, agarose is increasingly utilized in the medical industry. The aim of this review is to present an overview of the applications of agarose hydrogels in bone tissue engineering, introducing agarose and its modified products as innovative solutions for bone regeneration. Additionally, the injectability of agarose hydrogels and their applications in bioprinting are also summarized. Data indicate that agarose will play an increasing role in current and future global medical sectors.

3D bioprinting technology for modeling vascular diseases and its application

In vitromodeling of vascular diseases provides a useful platform for drug screening and mechanistic studies, by recapitulating the essential structures and physiological characteristics of the native tissue. Bioprinting is an emerging technique that offers high-resolution 3D capabilities, which have recently been employed in the modeling of various tissues and associated diseases. Blood vessels are composed of multiple layers of distinct cell types, and experience different mechanical conditions depending on the vessel type. The intimal layer, in particular, is directly exposed to such hemodynamic conditions inducing shear stress, which in turn influence vascular physiology. 3D bioprinting techniques have addressed the structural limitations of the previous vascular models, by incorporating supporting cells such as smooth muscle cells, geometrical properties such as dilation, curvature, or branching, or mechanical stimulation such as shear stress and pulsatile pressure. This paper presents a review of the physiology of blood vessels along with the pathophysiology of the target diseases including atherosclerosis, thrombosis, aneurysms, and tumor angiogenesis. Additionally, it discusses recent advances in fabricatingin vitro3D vascular disease models utilizing bioprinting techniques, while addressing the current challenges and future perspectives for the potential clinical translation into therapeutic interventions.

Current developments in 3D printing technology for orthopedic trauma: A review

Three-dimensional (3D) printing technology has emerged as a revolutionary tool in orthopedic trauma surgery, offering unprecedented opportunities for personalized patient care. This comprehensive review explores the current developments and applications of 3D printing in orthopedic trauma, highlighting its potential to address complex surgical challenges. We provide an in-depth analysis of various 3D printing technologies applicable to orthopedic surgery, including vat photopolymerization, material extrusion, powder bed fusion, and sheet lamination. The review examines the use of 3D printing in preoperative planning, surgical simulation, and the creation of patient-specific implants and surgical guides. We discuss applications across different anatomical regions, including upper limb, lower limb, and pelvic and spinal trauma. Evidence from recent studies demonstrates that 3D printing-assisted surgeries can lead to reduced operative times, decreased blood loss, improved fracture reduction quality, and potentially better clinical outcomes. This review synthesizes the latest research and clinical experiences, providing insights into the current state of 3D printing in orthopedic trauma and its future perspectives. As the technology continues to evolve, 3D printing holds promise for increasingly personalized and effective treatments in orthopedic trauma care, potentially transforming surgical practices and improving patient outcomes.

Biofabrication and simulation techniques for gut-on-a-chip

Biomimetic gut models show promise for enhancing our understanding of intestinal disorder pathogenesis and accelerating therapeutic strategy development. Currentin vitromodels predominantly comprise traditional static cell culture and animal models. Static cell culture lacks the precise control of the complex microenvironment governing human intestinal function. Animal models provide greater microenvironment complexity but fail to accurately replicate human physiological conditions due to interspecies differences. As the available models do not accurately reflect the microphysiological environment and functions of the human intestine, their applications are limited. An optimal approach to intestinal modeling is yet to be developed, but the field will probably benefit from advances in biofabrication techniques. This review highlights biofabrication strategies for constructing biomimetic intestinal models and research approaches for simulating key intestinal physiological features. We also discuss potential biomedical applications of these models and provide an outlook on multi-scale intestinal modeling.

Multi-material Gradient Printing Using Meniscus-enabled Projection Stereolithography (MAPS)

Light-based additive manufacturing methods have been widely used to print high-resolution 3D structures for applications in tissue engineering, soft robotics, photonics, and microfluidics, among others. Despite this progress, multi-material printing with these methods remains challenging due to constraints associated with hardware modifications, control systems, cross-contamination, waste, and resin properties. Here, we report a new printing platform coined Meniscus-enabled Projection Stereolithography (MAPS), a vat-free method that relies on generating and maintaining a resin meniscus between a crosslinked structure and bottom window to print lateral, vertical, discrete, or gradient multi-material 3D structures with no waste and user-defined mixing between layers. We show that MAPS is compatible with a wide range of resins and can print complex multi-material 3D structures without requiring specialized hardware, software, or complex washing protocols. MAPS's ability to print structures with microscale variations in mechanical stiffness, opacity, surface energy, cell densities, and magnetic properties provides a generic method to make advanced materials for a broad range of applications.

Development of Hydrogels Fabricated via Stereolithography for Bioengineering Applications

The architectures of hydrogels fabricated with stereolithography (SLA) 3D printing systems have played various roles in bioengineering applications. Typically, the SLA systems successively illuminated light to a layer of photo-crosslinkable hydrogel precursors for the fabrication of hydrogels. These SLA systems can be classified into point-scanning types and digital micromirror device (DMD) types. The point-scanning types form layers of hydrogels by scanning the precursors with a focused light, while DMD types illuminate 2D light patterns to the precursors to form each hydrogel layer at once. Overall, SLA systems were cost-effective and allowed the fabrication of hydrogels with good shape fidelity and uniform mechanical properties. As a result, hydrogel constructs fabricated with the SLA 3D printing systems were used to regenerate tissues and develop lab-on-a-chip devices and native tissue-like models.

A review of graded scaffolds made by additive manufacturing for tissue engineering: design, fabrication and properties

The emergence of tissue engineering (TE) has provided new vital means for human body tissue/organ repair. TE scaffolds can provide temporary structural support for cell attachment, growth, and proliferation, until the body restores the mechanical and biological properties of the host tissues. Since native tissues are inhomogeneous and in many situations are graded structures for performing their unique functions, graded scaffolds have become increasingly attractive for regenerating particular types of tissues, which aim to offer a more accurate replication of native interactions and functions. Importantly, the advances introduced by additive manufacturing (AM) have now enabled more design freedom and are capable of tailoring both structural and compositional gradients within a single scaffold. In this context, graded TE scaffolds fabricated by AM technologies have been attracting increasing attention. In this review, we start with an introduction of common graded structures in the human body and analyse the advantages and strengths of AM-formed graded scaffolds. Various AM technologies that can be leveraged to produce graded scaffolds are then reviewed based on non-cellular 3D printing and cell-laden 3D bioprinting. The comparisons among various AM technologies for fabricating graded scaffolds are presented. Subsequently, we propose several types of gradients, structural, material, biomolecular and multi-gradients for scaffolds, and highlight the design methods, resulting mechanical properties and biological responses. Finally, current status, challenges and perspectives for AM in developing graded scaffolds are exhibited and discussed.

Novel Soft Dosage Forms for Paediatric Applications: Can We 3D-Print Them or Not?

Over the past years, numerous novel dosage forms, including gels, have been investigated for paediatric treatment due to the need to provide flexible dose adjustment possibilities, as well as a patient-friendly approach to drug delivery. Simultaneously, 3D printing technology is continuously advancing and gaining interest as a tool for personalised formulation development. Multiple additive manufacturing methods, including the semi-solid extrusion, especially used in gel printing, provide flexibility regarding the dose of active ingredients and the adjustment of the design of soft dosage forms. 3D printing techniques can be considered as a possible answer to the demand for medicines tailored to small patients' needs. This review intends to present an overview of the current possibilities, comparing gel-like and non-gel-formulated dosage forms and crucial aspects of developing those cutting-edge dosage forms by 3D printing. This paper discusses soft formulations such as chewing gums, which still require extensive evaluation, and explores the question of the three-dimensional printing process. Furthermore, it highlights soft dosage forms, such as gel-based gummies and hydrogels, for which 3D fabrication has been intensively studied in previous years. However, the research still needs to advance.

Hydrogels for Cardiac Tissue Regeneration: Current and Future Developments

Myocardial infarction remains a leading cause of death worldwide due to the heart's limited regenerative capability and the current lack of viable therapeutic solutions. Therefore, there is an urgent need to develop effective treatment options to restore cardiac function after a heart attack. Stem cell-derived cardiac cells have been extensively utilised in cardiac tissue regeneration studies. However, the use of Matrigel as a substrate for the culture and maturation of these cells has been a major limitation for the translation of this research into clinical application. Hydrogels are emerging as a promising system to overcome this problem. They are biocompatible and can provide stem cells with a supportive scaffold that mimics the extracellular matrix, which is essential for repairing damaged tissue in the myocardium after an infarction. Thus, hydrogels provide an alternative and reproducible option in addressing myocardial infarction due to their unique potential therapeutic benefits. This review explores the different types of natural and synthetic polymers used to create hydrogels and their various delivery methods, the most common being via injection and cardiac patches and other applications such as bioprinting. Many challenges remain before hydrogels can be used in a clinical setting, but they hold great promise for the future of cardiac tissue regeneration.

Developing 3D bioprinting for organs-on-chips

Organs-on-chips (OoCs) have significantly advanced biomedical research by precisely reconstructing human microphysiological systems with biomimetic functions. However, achieving greater structural complexity of cell cultures on-chip for enhanced biological mimicry remains a challenge. To overcome these challenges, 3D bioprinting techniques can be used in directly building complex 3D cultures on chips, facilitating the in vitro engineering of organ-level models. Herein, we review the distinctive features of OoCs, along with the technical and biological challenges associated with replicating complex organ structures. We discuss recent bioprinting innovations that simplify the fabrication of OoCs while increasing their architectural complexity, leading to breakthroughs in the field and enabling the investigation of previously inaccessible biological problems. We highlight the challenges for the development of 3D bioprinted OoCs, concluding with a perspective on future directions aimed at facilitating their clinical translation.

Digital light processing printing of non-modified protein-only compositions

This study explores the utilization of digital light processing (DLP) printing to fabricate complex structures using native gelatin as the sole structural component for applications in biological implants. Unlike approaches relying on synthetic materials or chemically modified biopolymers, this research harnesses the inherent properties of gelatin to create biocompatible structures. The printing process is based on a crosslinking mechanism using a di-tyrosine formation initiated by visible light irradiation. Formulations containing gelatin were found to be printable at the maximum documented concentration of 30 wt%, thus allowing the fabrication of overhanging objects and open embedded. Cell adhesion and growth onto and within the gelatin-based 3D constructs were evaluated by examining two implant fabrication techniques: (1) cell seeding onto the printed scaffold and (2) printing compositions that contain cells (cell-laden). The preliminary biological experiments indicate that both the cell-seeding and cell-laden strategies enable making 3D cultures of chondrocytes within the gelatin constructs. The mechanical properties of the gelatin scaffolds have a compressive modulus akin to soft tissues, thus enabling the growth and proliferation of cells, and later degrade as the cells differentiate and form a grown cartilage. This study underscores the potential of utilizing non-modified protein-only bioinks in DLP printing to produce intricate 3D objects with high fidelity, paving the way for advancements in regenerative tissue engineering.

Advances in 3D bioprinting to enhance translational applications in bone tissue engineering and regenerative medicine

Bone defects are due to trauma, infections, tumors, or aging, including bone fractures, bone metastases, osteoporosis, or osteoarthritis. The global burden of these demands research into innovative strategies that overcome the limitations of conventional autografts. In this sense, the development of three-dimensional (3D) bioprinting has emerged as a promising approach in the field of tissue engineering and regenerative medicine (TERM) for the on-demand generation and transplantation of tissues and organs, including bone. It combines biological materials and living cells, which are precisely positioned layer by layer. Despite obtaining some promising results, 3D bioprinting of bone tissue still faces several challenges, such as generating an effective vascular network to increase tissue viability. In this review, we aim to collect the main knowledge on methods and techniques of 3D bioprinting. Then, we will review the main biomaterials, their composition, and the rationale for their application in 3D bioprinting for the TERM of bone.

Tuning Star Polymer Architecture to Tailor Secondary Structures and Mechanical Properties of Diblock Polypeptide Hydrogels for Direct Ink Writing

Hydrogel three-dimensional (3D) printing has emerged as a highly valuable fabrication tool for applications ranging from electronics and biomedicine. While conventional hydrogels such as gelatin, alginate, and hyaluronic acid satisfy biocompatibility requirements, they distinctly lack reproducibility in terms of mechanical properties and 3D printability. Aiming to offer a high-performance alternative, here we present a range of amphiphilic star-shaped diblock copolypeptides of l-glutamate and l-leucine residues with different topologies. Hydrophobic side chains of the l-leucine polymer block drive conformational self-assembly in water, spontaneously forming hydrogels with tunable mechanical properties, through variation of star topology. Their amenable shear-thinning and self-recovery properties render them suitable as hydrogel inks for direct ink writing. Well-defined 3D-printed structures can be readily generated and rapidly photo-cross-linked using visible light (405 nm) after methacrylamide functionalization, while hydrogel inks demonstrate good biocompatibility with top-seeded and encapsulated MC3T3 cells.

3D Printing-Based Hydrogel Dressings for Wound Healing

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

Light-based 3D bioprinting techniques for illuminating the advances of vascular tissue engineering

Vascular tissue engineering faces significant challenges in creating in vitro vascular disease models, implantable vascular grafts, and vascularized tissue/organ constructs due to limitations in manufacturing precision, structural complexity, replicating the composited architecture, and mimicking the mechanical properties of natural vessels. Light-based 3D bioprinting, leveraging the unique advantages of light including high resolution, rapid curing, multi-material adaptability, and tunable photochemistry, offers transformative solutions to these obstacles. With the emergence of diverse light-based 3D bioprinting techniques and innovative strategies, the advances in vascular tissue engineering have been significantly accelerated. This review provides an overview of the human vascular system and its physiological functions, followed by an in-depth discussion of advancements in light-based 3D bioprinting, including light-dominated and light-assisted techniques. We explore the application of these technologies in vascular tissue engineering for creating in vitro vascular disease models recapitulating key pathological features, implantable blood vessel grafts, and tissue analogs with the integration of capillary-like vasculatures. Finally, we provide readers with insights into the future perspectives of light-based 3D bioprinting to revolutionize vascular tissue engineering.

Photocrosslinkable Biomaterials for 3D Bioprinting: Mechanisms, Recent Advances, and Future Prospects

Constructing scaffolds with the desired structures and functions is one of the main goals of tissue engineering. Three-dimensional (3D) bioprinting is a promising technology that enables the personalized fabrication of devices with regulated biological and mechanical characteristics similar to natural tissues/organs. To date, 3D bioprinting has been widely explored for biomedical applications like tissue engineering, drug delivery, drug screening, and in vitro disease model construction. Among different bioinks, photocrosslinkable bioinks have emerged as a powerful choice for the advanced fabrication of 3D devices, with fast crosslinking speed, high resolution, and great print fidelity. The photocrosslinkable biomaterials used for light-based 3D printing play a pivotal role in the fabrication of functional constructs. Herein, this review outlines the general 3D bioprinting approaches related to photocrosslinkable biomaterials, including extrusion-based printing, inkjet printing, stereolithography printing, and laser-assisted printing. Further, the mechanisms, advantages, and limitations of photopolymerization and photoinitiators are discussed. Next, recent advances in natural and synthetic photocrosslinkable biomaterials used for 3D bioprinting are highlighted. Finally, the challenges and future perspectives of photocrosslinkable bioinks and bioprinting approaches are envisaged.

High-throughput bioprinting of spheroids for scalable tissue fabrication

Tissue biofabrication mimicking organ-specific architecture and function requires physiologically-relevant cell densities. Bioprinting using spheroids can achieve this, but is limited due to the lack of practical, scalable techniques. This study presents HITS-Bio (High-throughput Integrated Tissue Fabrication System for Bioprinting), a multiarray bioprinting technique for rapidly positioning multiple spheroids simultaneously using a digitally-controlled nozzle array (DCNA). HITS-Bio achieves an unprecedented speed, ten times faster compared to existing techniques while maintaining high cell viability ( > 90%). The utility of HITS-Bio was exemplified in multiple applications, including intraoperative bioprinting with microRNA transfected human adipose-derived stem cell spheroids for calvarial bone regeneration ( ~ 30 mm3) in a rat model achieving a near-complete defect closure (bone coverage area of ~ 91% in 3 weeks and ~96% in 6 weeks). Additionally, the successful fabrication of scalable cartilage constructs (1 cm3) containing ~600 chondrogenic spheroids highlights its high-throughput efficiency (under 40 min per construct) and potential for repairing volumetric defects.

Advanced bioengineering strategies broaden the therapeutic landscape for corneal failure

The cornea acts as the eye foremost protective layer and is essential for its focusing power. Corneal blindness may arise from physical trauma or conditions like dystrophies, keratitis, keratoconus, or ulceration. While conventional treatments involve medical therapies and donor allografts-sometimes supplemented with keratoprostheses-these options are not suitable for all corneal defects. Consequently, the development of bioartificial corneal tissue has emerged as a critical research area, aiming to address the global shortage of human cornea donors. Bioengineered corneas hold considerable promise as substitutes, with the potential to replace either specific layers or the entire thickness of damaged corneas. This review first delves into the structural anatomy of the human cornea, identifying key attributes necessary for successful corneal tissue bioengineering. It then examines various corneal pathologies, current treatments, and their limitations. Finally, the review outlines the primary approaches in corneal tissue engineering, exploring cell-free, cell-based, and scaffold-based options as three emerging strategies to address corneal failure.

Bioinks and biofabrication techniques for biosensors development: A review

3D bioprinting technologies and bioink development are enabling significant advances in miniaturized and integrated biosensors. For example, bioreceptors can be immobilized within a porous 3D structure to significantly amplify the signal, while biocompatible and mechanically flexible systems uniquely enable wearable chem- and bio-sensors. This advancement is accelerating translation by enabling the production of high performance, reproducible, and flexible analytical devices. The formulation of the bioink plays a crucial role in determining the bio-functionality of the resulting printed structures, e.g., the porosity that allows the analyte to diffuse through the 3D structure, the affinity and avidity of the receptors, etc. This review explores the next generation of advanced bioinks for biosensor development and provides insights into the latest cutting-edge bioprinting technologies. The bioprinting methods available for biosensor fabrication including inkjet, extrusion, and laser-based bioprinting, are discussed. The advantages and limitations of each method are analysed, and recent advancements in bioprinting technologies are presented. The review then delves into the properties of advanced bioinks, such as biocompatibility, printability, stability, and applicability. Different types of advanced bioinks are explored, including multicomponent, stimuli-responsive, and conductive bioinks. Finally, the next generation of bioinks for biosensors is considered, identifying possible new opportunities and challenges. Overall, this literature review highlights the combined importance of bioink formulation and bioprinting methods for the development of high-performance analytical biosensors.

Visible-Light-Induced Silk Fibroin Hydrogels with Carbon Quantum Dots as Initiators for 3D Bioprinting Applications

Digital light processing (DLP) 3D bioprinting technology has attracted increasing attention in tissue engineering in recent years. However, it still faces significant technical and operational challenges such as cell carcinogenesis caused by prolonged exposure to ultraviolet light and the presence of heavy metal ions in complex photoinitiator systems. In this study, a novel strategy is designed to introduce carbon quantum dots into visible-light-induced silk fibroin bioink as initiators (CDs/SilMA) applied for DLP 3D bioprinting technology. The incorporation of carbon quantum dots facilitates the formation of precise hydrogel structures at 415 nm visible wavelength, enabling the creation of brain, bronchus, spine, and ear models. Replacing heavy metal photoinitiators with carbon quantum dots imparts fluorescence properties to the bioink and enhances its mechanical properties. Meanwhile, the fibroin protein-based hydrogel exhibits favorable properties, such as drug loading, slow release, degradability, and biocompatibility. This is the first study to propose the application of carbon quantum dots in silk fibroin-based bioink. Moreover, the resulting product demonstrates excellent compatibility with the DLP printing process, making it promising for practical applications in various tissue engineering scenarios with specific requirements.

Comprehensive review of the state-of-the-art in corneal 3D bioprinting, including regulatory aspects

The global shortage of corneal transplants has spurred an urgency in the quest for efficient treatments. This systematic review not only provides a concise overview of the current landscape of corneal morphology, physiology, diseases, and conventional treatments but crucially delves into the forefront of tissue engineering for corneal regeneration. Emphasizing cellular and acellular components, bioprinting techniques, and pertinent biological assays, it explores optimization strategies for manufacturing and cost-effectiveness. To bridge the gap between research and industrial production, the review outlines the essential regulatory strategy required in Europe, encompassing relevant directives, frameworks, and governing bodies. This comprehensive regulatory framework spans the entire process, from procuring initial components to marketing and subsequent product surveillance. In a pivotal shift towards the future, the review culminates by highlighting the latest advancements in this sector, particularly the integration of tissue therapy with artificial intelligence. This synergy promises substantial optimization of the overall process, paving the way for unprecedented breakthroughs in corneal regeneration. In essence, this review not only elucidates the current state of corneal treatments and tissue engineering but also outlines regulatory pathways and anticipates the transformative impact of artificial intelligence, providing a comprehensive guide for researchers, practitioners, and policymakers in the field.

mSLAb - An open-source masked stereolithography (mSLA) bioprinter

3D bioprinting is a tissue engineering approach using additive manufacturing to fabricate tissue equivalents for regenerative medicine or medical drug testing. For this purpose, biomaterials that provide the essential microenvironment to support the viability of cells integrated directly or seeded after printing are processed into three-dimensional (3D) structures. Compared to extrusion-based 3D printing, which is most commonly used in bioprinting, stereolithography (SLA) offers a higher printing resolution and faster processing speeds with a wide range of cell-friendly materials such as gelatin- or collagen-based hydrogels and SLA is, therefore, well suited to generate 3D tissue constructs. While there have been numerous publications of conversions and upgrades for extrusion-based printers, this is not the case for state-of-the-art SLA technology in bioprinting. The high cost of proprietary printers severely limits teaching and research in SLA bioprinting. With mSLAb, we present a low-cost and open-source high-resolution 3D bioprinter based on masked SLA (mSLA). mSLAb is based on an entry-level (€350) desktop mSLA printer (Phrozen Sonic Mini 4 K), equipped with temperature control and humidification of the printing chamber to enable the processing of cell-friendly hydrogels. Additionally, the build platform was redesigned for easy sample handling and microscopic analysis of the printed constructs. All modifications were done with off-the-shelf hardware and in-house designed 3D printed components, printed with the same printer that was being modified. We validated the system by printing macroscopic porous scaffolds as well as hollow channels from gelatin-based hydrogels as representative structures needed in tissue engineering.

Design considerations for digital light processing bioprinters

With the rapid development and popularization of additive manufacturing, different technologies, including, but not limited to, extrusion-, droplet-, and vat-photopolymerization-based fabrication techniques, have emerged that have allowed tremendous progress in three-dimensional (3D) printing in the past decades. Bioprinting, typically using living cells and/or biomaterials conformed by different printing modalities, has produced functional tissues. As a subclass of vat-photopolymerization bioprinting, digital light processing (DLP) uses digitally controlled photomasks to selectively solidify liquid photocurable bioinks to construct complex physical objects in a layer-by-layer manner. DLP bioprinting presents unique advantages, including short printing times, relatively low manufacturing costs, and decently high resolutions, allowing users to achieve significant progress in the bioprinting of tissue-like complex structures. Nevertheless, the need to accommodate different materials while bioprinting and improve the printing performance has driven the rapid progress in DLP bioprinters, which requires multiple pieces of knowledge ranging from optics, electronics, software, and materials beyond the biological aspects. This raises the need for a comprehensive review to recapitulate the most important considerations in the design and assembly of DLP bioprinters. This review begins with analyzing unique considerations and specific examples in the hardware, including the resin vat, optical system, and electronics. In the software, the workflow is analyzed, including the parameters to be considered for the control of the bioprinter and the voxelizing/slicing algorithm. In addition, we briefly discuss the material requirements for DLP bioprinting. Then, we provide a section with best practices and maintenance of a do-it-yourself DLP bioprinter. Finally, we highlight the future outlooks of the DLP technology and their critical role in directing the future of bioprinting. The state-of-the-art progress in DLP bioprinter in this review will provide a set of knowledge for innovative DLP bioprinter designs.

Beyond hype: unveiling the Real challenges in clinical translation of 3D printed bone scaffolds and the fresh prospects of bioprinted organoids

Bone defects pose significant challenges in healthcare, with over 2 million bone repair surgeries performed globally each year. As a burgeoning force in the field of bone tissue engineering, 3D printing offers novel solutions to traditional bone transplantation procedures. However, current 3D-printed bone scaffolds still face three critical challenges in material selection, printing methods, cellular self-organization and co-culture, significantly impeding their clinical application. In this comprehensive review, we delve into the performance criteria that ideal bone scaffolds should possess, with a particular focus on the three core challenges faced by 3D printing technology during clinical translation. We summarize the latest advancements in non-traditional materials and advanced printing techniques, emphasizing the importance of integrating organ-like technologies with bioprinting. This combined approach enables more precise simulation of natural tissue structure and function. Our aim in writing this review is to propose effective strategies to address these challenges and promote the clinical translation of 3D-printed scaffolds for bone defect treatment.

Light-based 3D bioprinting technology applied to repair and regeneration of different tissues: A rational proposal for biomedical applications

3D bioprinting technology, a subset of 3D printing technology, is currently witnessing widespread utilization in tissue repair and regeneration endeavors. In particular, light-based 3D bioprinting technology has garnered significant interest and favor. Central to its successful implementation lies the judicious selection of photosensitive polymers. Moreover, by fine-tuning parameters such as light irradiation time, choice of photoinitiators and crosslinkers, and their concentrations, the properties of the scaffolds can be tailored to suit the specific requirements of the targeted tissue repair sites. In this comprehensive review, we provide an overview of commonly utilized bio-inks suitable for light-based 3D bioprinting, delving into the distinctive characteristics of each material. Furthermore, we delineate strategies for bio-ink selection tailored to diverse repair locations, alongside methods for optimizing printing parameters. Ultimately, we present a coherent synthesis aimed at enhancing the practical application of light-based 3D bioprinting technology in tissue engineering, while also addressing current challenges and future prospects.

Computational Fluid Dynamics (CFD) Analysis of Bioprinting

Regenerative medicine has evolved with the rise of tissue engineering due to advancements in healthcare and technology. In recent years, bioprinting has been an upcoming approach to traditional tissue engineering practices, through the fabrication of functional tissue by its layer-by-layer deposition process. This overcomes challenges such as irregular cell distribution and limited cell density, and it can potentially address organ shortages, increasing transplant options. Bioprinting fully functional organs is a long stretch but the advancement is rapidly growing due to its precision and compatibility with complex geometries. Computational Fluid Dynamics (CFD), a carestone of computer-aided engineering, has been instrumental in assisting bioprinting research and development by cutting costs and saving time. CFD optimizes bioprinting by testing parameters such as shear stress, diffusivity, and cell viability, reducing repetitive experiments and aiding in material selection and bioprinter nozzle design. This review discusses the current application of CFD in bioprinting and its potential to enhance the technology that can contribute to the evolution of regenerative medicine.

Biofabrication with microbial cellulose: from bioadaptive designs to living materials

Nanocellulose is not only a renewable material but also brings functions that are opening new technological opportunities. Here we discuss a special subset of this material, in its fibrillated form, which is produced by aerobic microorganisms, namely, bacterial nanocellulose (BNC). BNC offers distinct advantages over plant-derived counterparts, including high purity and high degree of polymerization as well as crystallinity, strength, and water-holding capacity, among others. More remarkably, beyond classical fermentative protocols, it is possible to grow BNC on non-planar interfaces, opening new possibilities in the assembly of advanced bottom-up structures. In this review, we discuss the recent advances in the area of BNC-based biofabrication of three-dimensional (3D) designs by following solid- and soft-material templating. These methods are shown as suitable platforms to achieve bioadaptive constructs comprising highly interlocked biofilms that can be tailored with precise control over nanoscale morphological features. BNC-based biofabrication opens applications that are not possible by using traditional manufacturing routes, including direct ink writing of hydrogels. This review emphasizes the critical contributions of microbiology, colloid and surface science, as well as additive manufacturing in achieving bioadaptive designs from living matter. The future impact of BNC biofabrication is expected to take advantage of material and energy integration, residue utilization, circularity and social latitudes. Leveraging existing infrastructure, the scaleup of biofabrication routes will contribute to a new generation of advanced materials rooted in exciting synergies that combine biology, chemistry, engineering and material sciences.

Targeted Rapamycin Delivery via Magnetic Nanoparticles to Address Stenosis in a 3D Bioprinted in Vitro Model of Pulmonary Veins

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.

An overview of nasal cartilage bioprinting: from bench to bedside

Nasal cartilage diseases and injuries are known as significant challenges in reconstructive medicine, affecting a substantial number of individuals worldwide. In recent years, the advent of three-dimensional (3D) bioprinting has emerged as a promising approach for nasal cartilage reconstruction, offering potential breakthroughs in the field of regenerative medicine. This paper provides an overview of the methods and challenges associated with 3D bioprinting technologies in the procedure of reconstructing nasal cartilage tissue. The process of 3D bioprinting entails generating a digital 3D model using biomedical imaging techniques and computer-aided design to integrate both internal and external scaffold features. Then, bioinks which consist of biomaterials, cell types, and bioactive chemicals, are applied to facilitate the precise layer-by-layer bioprinting of tissue-engineered scaffolds. After undergoing in vitro and in vivo experiments, this process results in the development of the physiologically functional integrity of the tissue. The advantages of 3D bioprinting encompass the ability to customize scaffold design, enabling the precise incorporation of pore shape, size, and porosity, as well as the utilization of patient-specific cells to enhance compatibility. However, various challenges should be considered, including the optimization of biomaterials, ensuring adequate cell viability and differentiation, achieving seamless integration with the host tissue, and navigating regulatory attention. Although numerous studies have demonstrated the potential of 3D bioprinting in the rebuilding of such soft tissues, this paper covers various aspects of the bioprinted tissues to provide insights for the future development of repair techniques appropriate for clinical use.

Research progress of photo-crosslink hydrogels in ophthalmology: A comprehensive review focus on the applications

Hydrogel presents a three-dimensional polymer network with high water content. Over the past decade, hydrogel has developed from static material to intelligent material with controllable response. Various stimuli are involved in the formation of hydrogel network, among which photo-stimulation has attracted wide attention due to the advantages of controllable conditions, which has a good application prospect in the treatment of ophthalmic diseases. This paper reviews the application of photo-crosslink hydrogels in ophthalmology, focusing on the types of photo-crosslink hydrogels and their applications in ophthalmology, including drug delivery, tissue engineering and 3D printing. In addition, the limitations and future prospects of photo-crosslink hydrogels are also provided.

Droplet bioprinting of acellular and cell-laden structures at high-resolutions

Advances in digital light projection(DLP) based (bio) printers have made printing of intricate structures at high resolution possible using a wide range of photosensitive bioinks. A typical setup of a DLP bioprinter includes a vat or reservoir filled with liquid bioink, which presents challenges in terms of cost associated with bioink synthesis, high waste, and gravity-induced cell settling, contaminations, or variation in bioink viscosity during the printing process. Here, we report a vat-free, low-volume, waste-free droplet bioprinting method capable of rapidly printing 3D soft structures at high resolution using model bioinks and model cells. A multiphase many-body dissipative particle dynamics model was developed to simulate the dynamic process of droplet-based DLP printing and elucidate the roles of surface wettability and bioink viscosity. Process variables such as light intensity, photo-initiator concentration, and bioink formulations were optimized to print 3D soft structures (∼0.4-3 kPa) with a typical layer thickness of 50µm, an XY resolution of 38 ± 1.5μm and Z resolution of 237 ± 5.4µm. To demonstrate its versatility, droplet bioprinting was used to print a range of acellular 3D structures such as a lattice cube, a Mayan pyramid, a heart-shaped structure, and a microfluidic chip with endothelialized channels. Droplet bioprinting, performed using model C3H/10T1/2 cells, exhibited high viability (90%) and cell spreading. Additionally, microfluidic devices with internal channel networks lined with endothelial cells showed robust monolayer formation while osteoblast-laden constructs showed mineral deposition upon osteogenic induction. Overall, droplet bioprinting could be a low-cost, no-waste, easy-to-use, method to make customized bioprinted constructs for a range of biomedical applications.

Advanced 3D imaging and organoid bioprinting for biomedical research and therapeutic applications

Organoid cultures offer a valuable platform for studying organ-level biology, allowing for a closer mimicry of human physiology compared to traditional two-dimensional cell culture systems or non-primate animal models. While many organoid cultures use cell aggregates or decellularized extracellular matrices as scaffolds, they often lack precise biochemical and biophysical microenvironments. In contrast, three-dimensional (3D) bioprinting allows precise placement of organoids or spheroids, providing enhanced spatial control and facilitating the direct fusion for the formation of large-scale functional tissues in vitro. In addition, 3D bioprinting enables fine tuning of biochemical and biophysical cues to support organoid development and maturation. With advances in the organoid technology and its potential applications across diverse research fields such as cell biology, developmental biology, disease pathology, precision medicine, drug toxicology, and tissue engineering, organoid imaging has become a crucial aspect of physiological and pathological studies. This review highlights the recent advancements in imaging technologies that have significantly contributed to organoid research. Additionally, we discuss various bioprinting techniques, emphasizing their applications in organoid bioprinting. Integrating 3D imaging tools into a bioprinting platform allows real-time visualization while facilitating quality control, optimization, and comprehensive bioprinting assessment. Similarly, combining imaging technologies with organoid bioprinting can provide valuable insights into tissue formation, maturation, functions, and therapeutic responses. This approach not only improves the reproducibility of physiologically relevant tissues but also enhances understanding of complex biological processes. Thus, careful selection of bioprinting modalities, coupled with appropriate imaging techniques, holds the potential to create a versatile platform capable of addressing existing challenges and harnessing opportunities in these rapidly evolving fields.

Engineered Living Material Bioreactors with Tunable Mechanical Properties using Vat Photopolymerization

3D-printed engineered living materials (ELM) are promising bioproduction platforms for agriculture, biotechnology, sustainable energy, and green technology applications. However, the design of these platforms faces several challenges, such as the processability of these materials into complex form factors and control over their mechanical properties. Herein, ELM are presented as 3D-printed bioreactors with arbitrary shape geometries and tunable mechanical properties (moduli and toughness). Poly(ethylene glycol) diacrylate (PEGDA) is used as the precursor to create polymer networks that encapsulate the microorganisms during the vat photopolymerization process. A major limitation of PEGDA networks is their propensity to swell and fracture when submerged in water. The authors overcame this issue by adding glycerol to the resin formulation to 3D print mechanically tough ELM hydrogels. While polymer concentration affects the modulus and reduces bioproduction, ELM bioreactors still maintain their metabolic activity regardless of polymer concentration. These ELM bioreactors have the potential to be used in different applications for sustainable architecture, food production, and biomedical devices that require different mechanical properties from soft to stiff.

3D bioprinting of microorganisms: principles and applications

In recent years, the ability to create intricate, live tissues and organs has been made possible thanks to three-dimensional (3D) bioprinting. Although tissue engineering has received a lot of attention, there is growing interest in the use of 3D bioprinting for microorganisms. Microorganisms like bacteria, fungi, and algae, are essential to many industrial bioprocesses, such as bioremediation as well as the manufacture of chemicals, biomaterials, and pharmaceuticals. This review covers current developments in 3D bioprinting methods for microorganisms. We go over the bioink compositions designed to promote microbial viability and growth, taking into account factors like nutrient delivery, oxygen supply, and waste elimination. Additionally, we investigate the most important bioprinting techniques, including extrusion-based, inkjet, and laser-assisted approaches, as well as their suitability with various kinds of microorganisms. We also investigate the possible applications of 3D bioprinted microbes. These range from constructing synthetic microbial consortia for improved metabolic pathway combinations to designing spatially patterned microbial communities for enhanced bioremediation and bioprocessing. We also look at the potential for 3D bioprinting to advance microbial research, including the creation of defined microenvironments to observe microbial behavior. In conclusion, the 3D bioprinting of microorganisms marks a paradigm leap in microbial bioprocess engineering and has the potential to transform many application areas. The ability to design the spatial arrangement of various microorganisms in functional structures offers unprecedented possibilities and ultimately will drive innovation.

Applications, advancements, and challenges of 3D bioprinting in organ transplantation

To date, organ transplantation remains an effective method for treating end-stage diseases of various organs. In recent years, despite the continuous development of organ transplantation technology, a variety of problems restricting its progress have emerged one after another, and the shortage of donors is at the top of the list. Bioprinting is a very useful tool that has huge application potential in many fields of life science and biotechnology, among which its use in medicine occupies a large area. With the development of bioprinting, advances in medicine have focused on printing cells and tissues for tissue regeneration and reconstruction of viable human organs, such as the heart, kidneys, and bones. In recent years, with the development of organ transplantation, three-dimensional (3D) bioprinting has played an increasingly important role in this field, giving rise to many unsolved problems, including a shortage of organ donors. This review respectively introduces the development of 3D bioprinting as well as its working principles and main applications in the medical field, especially in the applications, and advancements and challenges of 3D bioprinting in organ transplantation. With the continuous update and progress of printing technology and its deeper integration with the medical field, many obstacles will have new solutions, including tissue repair and regeneration, organ reconstruction, etc., especially in the field of organ transplantation. 3D printing technology will provide a better solution to the problem of donor shortage.

Fabrication and properties of PLA/β-TCP scaffolds using liquid crystal display (LCD) photocuring 3D printing for bone tissue engineering

Introduction: Bone defects remain a thorny challenge that clinicians have to face. At present, scaffolds prepared by 3D printing are increasingly used in the field of bone tissue repair. Polylactic acid (PLA) has good thermoplasticity, processability, biocompatibility, and biodegradability, but the PLA is brittle and has poor osteogenic performance. Beta-tricalcium phosphate (β-TCP) has good mechanical properties and osteogenic induction properties, which can make up for the drawbacks of PLA. Methods: In this study, photocurable biodegradable polylactic acid (bio-PLA) was utilized as the raw material to prepare PLA/β-TCP slurries with varying β-TCP contents (β-TCP dosage at 0%, 10%, 20%, 30%, 35% of the PLA dosage, respectively). The PLA/β-TCP scaffolds were fabricated using liquid crystal display (LCD) light-curing 3D printing technology. The characterization of the scaffolds was assessed, and the biological activity of the scaffold with the optimal compressive strength was evaluated. The biocompatibility of the scaffold was assessed through CCK-8 assays, hemocompatibility assay and live-dead staining experiments. The osteogenic differentiation capacity of the scaffold on MC3T3-E1 cells was evaluated through alizarin red staining, alkaline phosphatase (ALP) detection, immunofluorescence experiments, and RT-qPCR assays. Results: The prepared scaffold possesses a three-dimensional network structure, and with an increase in the quantity of β-TCP, more β-TCP particles adhere to the scaffold surface. The compressive strength of PLA/β-TCP scaffolds exhibits a trend of initial increase followed by decrease with an increasing amount of β-TCP, reaching a maximum value of 52.1 MPa at a 10% β-TCP content. Degradation rate curve results indicate that with the passage of time, the degradation rate of the scaffold gradually increases, and the pH of the scaffold during degradation shows an alkaline tendency. Additionally, Live/dead staining and blood compatibility experiments suggest that the prepared PLA/β-TCP scaffold demonstrates excellent biocompatibility. CCK-8 experiments indicate that the PLA/β-TCP group promotes cell proliferation, and the prepared PLA/β-TCP scaffold exhibits a significant ability to enhance the osteogenic differentiation of MC3T3-E1 cells in vitro. Discussion: 3D printed LCD photocuring PLA/β-TCP scaffolds could improve surface bioactivity and lead to better osteogenesis, which may provide a unique strategy for developing bioactive implants in orthopedic applications.

The fabrication of the chitosan-based bioink for in vitro tissue repair and regeneration: A review

The repair and regeneration of the injured tissues or organs is a major challenge for biomedicine, and the emerging 3D bioprinting technology as a class of promising techniques in biomedical research for the development of tissue engineering and regenerative medicine. Chitosan-based bioinks, as the natural biomaterials, are considered as ideal materials for 3D bioprinting to design and fabricate the various scaffold due to their unique dynamic reversibility and fantastic biological properties. Our review aims to provide an overview of chitosan-based bioinks for in vitro tissue repair and regeneration, starting from modification of chitosan that affect these bioprinting processes. In addition, we summarize the advances in chitosan-based bioinks used in the various 3D printing strategies. Moreover, the biomedical applications of chitosan-based bioinks are discussed, primarily centered on regenerative medicine and tissue modeling engineering. Finally, current challenges and future opportunities in this field are discussed. The combination of chitosan-based bioinks and 3D bioprinting will hold promise for developing novel biomedical scaffolds for tissue or organ repair and regeneration.

[Photopolymerizable compositions for bone tissue regeneration]

The review considers methods of manufacturing photopolymerizable compositions for bone tissue repair, as well as polymers and photoinitiators used for this purpose. Their physical and biological properties are described. Examples of light-curing compositions used in biomedicine and tissue engineering are given. The prospects of photopolymerization development for the production of materials for bone tissue regeneration as a promising technology for application in dentistry, maxillofacial surgery and orthopedics are considered.

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

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

Development and Prospective Applications of 3D Membranes as a Sensor for Monitoring and Inducing Tissue Regeneration

For decades, tissue regeneration has been a challenging issue in scientific modeling and human practices. Although many conventional therapies are already used to treat burns, muscle injuries, bone defects, and hair follicle injuries, there remains an urgent need for better healing effects in skin, bone, and other unique tissues. Recent advances in three-dimensional (3D) printing and real-time monitoring technologies have enabled the creation of tissue-like membranes and the provision of an appropriate microenvironment. Using tissue engineering methods incorporating 3D printing technologies and biomaterials for the extracellular matrix (ECM) containing scaffolds can be used to construct a precisely distributed artificial membrane. Moreover, advances in smart sensors have facilitated the development of tissue regeneration. Various smart sensors may monitor the recovery of the wound process in different aspects, and some may spontaneously give feedback to the wound sites by releasing biological factors. The combination of the detection of smart sensors and individualized membrane design in the healing process shows enormous potential for wound dressings. Here, we provide an overview of the advantages of 3D printing and conventional therapies in tissue engineering. We also shed light on different types of 3D printing technology, biomaterials, and sensors to describe effective methods for use in skin and other tissue regeneration, highlighting their strengths and limitations. Finally, we highlight the value of 3D bioengineered membranes in various fields, including the modeling of disease, organ-on-a-chip, and drug development.

Preclinical Testing Techniques: Paving the Way for New Oncology Screening Approaches

Prior to clinical trials, preclinical testing of oncology drug candidates is performed by evaluating drug candidates with in vitro and in vivo platforms. For in vivo testing, animal models are used to evaluate the toxicity and efficacy of drug candidates. However, animal models often display poor translational results as many drugs that pass preclinical testing fail when tested with humans, with oncology drugs exhibiting especially poor acceptance rates. The FDA Modernization Act 2.0 promotes alternative preclinical testing techniques, presenting the opportunity to use higher complexity in vitro models as an alternative to in vivo testing, including three-dimensional (3D) cell culture models. Three-dimensional tissue cultures address many of the shortcomings of 2D cultures by more closely replicating the tumour microenvironment through a combination of physiologically relevant drug diffusion, paracrine signalling, cellular phenotype, and vascularization that can better mimic native human tissue. This review will discuss the common forms of 3D cell culture, including cell spheroids, organoids, organs-on-a-chip, and 3D bioprinted tissues. Their advantages and limitations will be presented, aiming to discuss the use of these 3D models to accurately represent human tissue and as an alternative to animal testing. The use of 3D culture platforms for preclinical drug development is expected to accelerate as these platforms continue to improve in complexity, reliability, and translational predictivity.

3D Printed Graphene and Graphene/Polymer Composites for Multifunctional Applications

Three-dimensional (3D) printing, alternatively known as additive manufacturing, is a transformative technology enabling precise, customized, and efficient manufacturing of components with complex structures. It revolutionizes traditional processes, allowing rapid prototyping, cost-effective production, and intricate designs. The 3D printed graphene-based materials combine graphene's exceptional properties with additive manufacturing's versatility, offering precise control over intricate structures with enhanced functionalities. To gain comprehensive insights into the development of 3D printed graphene and graphene/polymer composites, this review delves into their intricate fabrication methods, unique structural attributes, and multifaceted applications across various domains. Recent advances in printable materials, apparatus characteristics, and printed structures of typical 3D printing techniques for graphene and graphene/polymer composites are addressed, including extrusion methods (direct ink writing and fused deposition modeling), photopolymerization strategies (stereolithography and digital light processing) and powder-based techniques. Multifunctional applications in energy storage, physical sensor, stretchable conductor, electromagnetic interference shielding and wave absorption, as well as bio-applications are highlighted. Despite significant advancements in 3D printed graphene and its polymer composites, innovative studies are still necessary to fully unlock their inherent capabilities.

Advances in 3D Bioprinting: Techniques, Applications, and Future Directions for Cardiac Tissue Engineering

Cardiovascular diseases are the leading cause of morbidity and mortality in the United States. Cardiac tissue engineering is a direction in regenerative medicine that aims to repair various heart defects with the long-term goal of artificially rebuilding a full-scale organ that matches its native structure and function. Three-dimensional (3D) bioprinting offers promising applications through its layer-by-layer biomaterial deposition using different techniques and bio-inks. In this review, we will introduce cardiac tissue engineering, 3D bioprinting processes, bioprinting techniques, bio-ink materials, areas of limitation, and the latest applications of this technology, alongside its future directions for further innovation.

Recent Advances in Decellularized Extracellular Matrix-Based Bioinks for 3D Bioprinting in Tissue Engineering

In recent years, three-dimensional (3D) bioprinting has been widely utilized as a novel manufacturing technique by more and more researchers to construct various tissue substitutes with complex architectures and geometries. Different biomaterials, including natural and synthetic materials, have been manufactured into bioinks for tissue regeneration using 3D bioprinting. Among the natural biomaterials derived from various natural tissues or organs, the decellularized extracellular matrix (dECM) has a complex internal structure and a variety of bioactive factors that provide mechanistic, biophysical, and biochemical signals for tissue regeneration and remodeling. In recent years, more and more researchers have been developing the dECM as a novel bioink for the construction of tissue substitutes. Compared with other bioinks, the various ECM components in dECM-based bioink can regulate cellular functions, modulate the tissue regeneration process, and adjust tissue remodeling. Therefore, we conducted this review to discuss the current status of and perspectives on dECM-based bioinks for bioprinting in tissue engineering. In addition, the various bioprinting techniques and decellularization methods were also discussed in this study.

Generation of a Perfusable 3D Lung Cancer Model by Digital Light Processing

Lung cancer still has one of the highest morbidity and mortality rates among all types of cancer. Its incidence continues to increase, especially in developing countries. Although the medical field has witnessed the development of targeted therapies, new treatment options need to be developed urgently. For the discovery of new drugs, human cancer models are required to study drug efficiency in a relevant setting. Here, we report the generation of a non-small cell lung cancer model with a perfusion system. The bioprinted model was produced by digital light processing (DLP). This technique has the advantage of including simulated human blood vessels, and its simple assembly and maintenance allow for easy testing of drug candidates. In a proof-of-concept study, we applied gemcitabine and determined the IC₅₀ values in the 3D models and 2D monolayer cultures and compared the response of the model under static and dynamic cultivation by perfusion. As the drug must penetrate the hydrogel to reach the cells, the IC₅₀ value was three orders of magnitude higher for bioprinted constructs than for 2D cell cultures. Compared to static cultivation, the viability of cells in the bioprinted 3D model was significantly increased by approximately 60% in the perfusion system. Dynamic cultivation also enhanced the cytotoxicity of the tested drug, and the drug-mediated apoptosis was increased with a fourfold higher fraction of cells with a signal for the apoptosis marker caspase-3 and a sixfold higher fraction of cells positive for PARP-1. Altogether, this easily reproducible cancer model can be used for initial testing of the cytotoxicity of new anticancer substances. For subsequent in-depth characterization of candidate drugs, further improvements will be necessary, such as the generation of a multi-cell type lung cancer model and the lining of vascular structures with endothelial cells.