Hydrogel-based 3D bioprinting: A comprehensive review on cell-laden hydrogels, bioink formulations, and future perspectives

Biomimetic basement membranes: advances in materials, preparation techniques, and applications in in vitro biological models

In vitro biological model technology has become a cornerstone of modern biological research, driving advancements in drug screening, physiological and pathological studies, and tissue implantation applications. The natural basement membrane (BM), a homogeneous structure, provides critical physical and biological support for tissues and organs. To replicate its function, researchers have developed biomimetic BMs using advanced fabrication technologies, which are increasingly applied to in vitro models. This review explores the materials, preparation techniques, and applications of biomimetic BMs across various biological models, highlighting their advantages and limitations. Additionally, it discusses recent progress in the field and identifies current challenges in achieving BM simulations that closely mimic native structures. Future directions and recommendations are provided to guide the development of high-performance biomimetic BM materials and their manufacturing processes.

Synthesis and characterization of photo-cross-linkable quince seed-based hydrogels for soft tissue engineering applications

The convenience, versatility, and biocompatibility of photocrosslinkable hydrogel precursors make them promising candidates for developing tissue engineering scaffolds. However, the current library of photosensitive materials is limited. This study reports, for the first time, the modification of quince seed mucilage (QS) with glycidyl methacrylate (GM), resulting in the synthesis of methacrylated QS (QSGM). The chemical composition and structure of QS were analyzed. The effects of reaction time, temperature, QS concentration, and GM/QS ratio on the degree of methacrylation, as well as the physicochemical, rheological, mechanical, and biological properties of the synthesized materials were explored. Chemical characterization using 1H NMR and FTIR confirmed the successful methacrylation of QS. Hydrogels fabricated from QSGMs at a 0.5 wt% concentration exhibited high swelling ratios of 320 to 580 g/g, and compressive strengths between 0.6 ± 0.1 and 1.2 ± 0.3 kPa. No significant changes in the rheological properties of hydrogel precursors were observed. Moreover, QSGM-based hydrogels supported cell encapsulation for 14 days with minimal cytotoxicity and immune cell activation. Finally, as a proof of concept, the potential use of QSGM for 3D printing was demonstrated. Overall, the results highlight the significant potential of QSGMs as a biomaterial of choice for soft tissue engineering applications.

Spheroids from Epithelial and Mesenchymal Cell Phenotypes as Building Blocks in Bioprinting (Review)

Most tissues and organs are based on cells of the epithelial and mesenchymal phenotypes. Epithelial cells build protective barriers, have a key role in absorption and secretion, and participate in metabolism. Characterized by high plasticity and ability to migrate, mesenchymal cells ensure structural support, promote tissue restoration and are important for matrix remodeling. Interaction between these two cell types is critical for maintaining the body integrity and functioning. Modern tissue engineering is aimed at creation of artificial tissues and organs that have the required cellular composition, mechanical properties and functional potential for medical usage. One of the most popular methods of tissue engineering is 3D bioprinting, which allows creating complex three-dimensional structures with specified characteristics. Recently, special attention has been paid to bioprinting with spheroids being three-dimensional cellular aggregates that can be used as building blocks for tissue-engineered structures. Due to numerous cell-to-cell contacts and accumulation of extracellular matrix, spheroids ensure conditions allowing to form anatomical tissues and organs. To optimize bioprinting conditions, one shall precisely understand the mechanical properties of spheroids, as they directly affect the ability of cells to migrate and fuse, and thus the rate of construct formation and its overall morphology. This review summarizes the available data on the differences in mechanical properties of epithelial and mesenchymal spheroids, examines methods for their co-culturing in various applications of regenerative medicine, as well as analyzes the peculiarities of their use in different bioprinting methods to obtain high-quality tissue constructs.

3D-printed and In-situ prepared hydrogel anti-bacterial wound patch with silver nanoparticle embedded matrix

The application of wearable hydrogel wound patches has great potential in advancing the field of medicine. However, for high reach and large-scale utilization, the fabrication process of wearable hydrogel wound patches needs to be low-cost, reliable, and have high throughput. Therefore, the incorporation of 3D-printing technology helps in providing a starting point for flexible, high throughput, mechanically enhanced, low-cost, and reliable antibacterial wound patches. 3D-printed patches can perform antibacterial behavior while exhibiting a fast fabrication process in a time range of less than 3 h. The fabricated patch exhibited good water retention, water vapor transmission rates a porosity values indicating that it has a promising potential to be commercialized as a wound patch.

Solving Challenges in Microalgae-Based Living Materials

Engineered living materials (ELMs) integrate aspects of material science and biology into a unique platform, leading to materials and devices with features of life. Among those, ELMs containing microalgae have received increased attention due to the many benefits photosynthetic organisms provide. Due to their relatively recent occurrence, photosynthetic ELMs still face many challenges related to reliability, lifetime, scalability, and more, often based on the complicated crosstalk of cellular, material-based, and environmental variables in time. This Viewpoint aims to summarize potential avenues for improving ELMs, beginning with an emphasis on understanding the cell's perspective and the potential stresses imposed on them due to recurring flaws in many current ELMs. Potential solutions and their ease of implementation will be discussed, ranging from choice of organism, adjustments to the ELM design, to various genetic modification tools, so as to achieve ELMs with longer lifetime and improved functionality.

Development of a Novel Hybprinter-SAM for Functionally Graded Tissue Engineering Constructs with Patterned and Localized Biochemical Signals

Engineering native-mimetic tissue constructs is challenging due to their intricate biological and structural gradients. To address this, Hybprinter-SAM was developed by integrating three bioprinting technologies: syringe extrusion (SE), acoustic droplet ejection (ADE) and molten material extrusion (MME). This system not only enables the creation of mechanical gradients by integrating soft and rigid materials spanning 7 order magnitude of stiffness but also facilitates precise patterning and controlled localization of biochemical signals within printed scaffolds. This capability is beneficial in replicating the complexity of native tissues to enhance functionality. Both the printing process and biomaterials were optimized to balance printability, mechanical integrity, and biocompatibility. As a proof of concept, Hybprinter-SAM was used in a bone-tendon regeneration study to engineer a multi-material construct with patterned fibroblast growth factor 2 (FGF-2), resulting in markers indicative of fibrocartilage development. These findings highlight the potential of Hybprinter-SAM as a versatile platform for diverse tissue engineering applications that require complex, functionally graded tissue constructs.

Advances in three-dimensional printing of hydrogel formulations for vascularized tissue and organ regeneration

Over the last decades, three-dimensional (3D) printing has emerged as one of the most promising alternative tissue and organ regeneration technologies. Recent advances in 3D printing technology, particularly in hydrogel-derived bioink formulations, offer promising solutions for fabricating intricate, biomimetic scaffolds that promote vascularization. In this review, we presented numerous studies that have been conducted to fabricate 3D-printed hydrogel vascularized constructs with significant advancements in printing integumentary systems, cardiovascular systems, vascularized bone tissues, skeletal muscles, livers, and kidneys. Furthermore, this work also discusses the engineering considerations, current challenges, proposed solutions, and future outlooks of 3D bioprinting.

Pioneering the Future of Oral Healthcare: Bioprinting and Its Transformative Clinical Potential in Dentistry

Bioprinting is revolutionizing the field of dentistry by enabling the fabrication of complex dental tissues using advanced techniques like inkjet, extrusion-based, and laser-assisted bioprinting. These methods allow for the precise placement of cells and materials to regenerate dental pulp, periodontal tissues, alveolar bone, and temporomandibular joint structures. Hydrogels, composite bioinks, and cell-laden bioinks play a crucial role in scaffold formation and improving cell viability. Preclinical models have demonstrated the potential of bioprinting for tissue regeneration and dental implants, with early clinical trials showing promising results. However, challenges remain, including scalability, material selection, immune response, and regulatory approval. Future advancements in multi-material bioprinting, real-time monitoring, and personalized treatment approaches will expand clinical applications of bioprinting, driving innovation in oral healthcare and improving patient outcomes.

Advanced Hydrogels: Enhancing Tissue Bioengineering with RGD Peptides and Carbon Nanomaterials

The advancement of tissue engineering (TE) is driven by the development of scaffolds that mimic the mechanical, spatial, and biological environment of the extracellular matrix (ECM), crucial for regulating cell behavior and tissue repair. Hydrogels, 3D networks of polymer chains, are particularly suited for TE due to their high biocompatibility, ability to mimic tissue water content, facilitate cell migration, sustain growth factor release, and offer controllable physical properties. However, hydrogels mimicking the ECM often face challenges related to cell adhesion due to the absence of specific receptors. This issue can be addressed by incorporating ECM components into the polymer matrix, such as the peptide sequence arginine-glycine-aspartic acid (RGD), known for its role in cell adhesion. Additionally, carbon nanomaterials (CNMs) offer unique physicochemical properties that can improve scaffold-cell interactions. Despite the potential benefits, there are limited reports on their combination. RGD-CNM hydrogels enable a more accurate emulation of the natural cellular environment, enhancing tissue engineering applications. This hybrid approach may promote robust cell adhesion along with exceptional mechanical and electrical properties. This review outlines the potential benefits of these hybrid scaffolds and their synergistic potential, aiming to inspire new research directions in this innovative field.

Progress in Nanotechnology for Treating Ocular Surface Chemical Injuries: Reflecting on Advances in Ophthalmology

Ocular surface chemical injuries often result in permanent visual impairment and necessitate complex, long-term treatments. Immediate and extensive irrigation serves as the first-line intervention, followed by various therapeutic protocols applied throughout different stages of the condition. To optimize outcomes, conventional regimens increasingly incorporate biological agents and surgical techniques. In recent years, nanotechnology has made significant strides, revolutionizing the management of ocular surface chemical injuries by enabling sustained drug release, enhancing treatment efficacy, and minimizing side effects. This review provides a comprehensive analysis of the etiology, epidemiology, classification, and conventional therapies for ocular chemical burns, with a special focus on nanotechnology-based drug delivery systems in managing ocular surface chemical injuries. Twelve categories of nanocarrier platforms are examined, including liposomes, nanoemulsions, nanomicelles, nanowafers, nanostructured lipid carriers, nanoparticles, hydrogels, dendrimers, nanocomplexes, nanofibers, nanozymes, and nanocomposite materials, highlighting their advantages in targeted delivery, biocompatibility, and improved healing efficacy. Additionally, current challenges and limitations in the field are discussed and the future potential of nanotechnology in treating ocular diseases is explored. This review presents the most extensive examination of this topic to date, aiming to link recent advancements with broader therapeutic strategies.

Recent advances in 3D bioprinted polysaccharide hydrogels for biomedical applications: A comprehensive review

Polysaccharide hydrogels, which can mimic the natural extracellular matrix and possess appealing physicochemical and biological characteristics, have emerged as significant bioinks for 3D bioprinting. They are highly promising for applications in tissue engineering and regenerative medicine because of their ability to enhance cell adhesion, proliferation, and differentiation in a manner akin to the natural cellular environment. This review comprehensively examines the fabrication methods, characteristics, and applications of polysaccharide hydrogel-driven 3D bioprinting, underscoring its potential in tissue engineering, drug delivery, and regenerative medicine. To contribute pertinent knowledge for future research in this field, this review critically examines key aspects, including the chemistry of carbohydrates, manufacturing techniques, formulation of bioinks, and characterization of polysaccharide-based hydrogels. Furthermore, this review explores the primary advancements and applications of 3D-printed polysaccharide hydrogels, encompassing drug delivery systems with controlled release kinetics and targeted therapy, along with tissue-engineered constructs for bone, cartilage, skin, and vascular regeneration. The use of these 3D bioprinted hydrogels in innovative research fields, including disease modeling and drug screening, is also addressed. Despite notable progress, challenges, including modulating the chemistry and properties of polysaccharides, enhancing bioink printability and mechanical properties, and achieving long-term in vivo stability, have been highlighted.

Artificial Intelligence-Driven Modeling for Hydrogel Three-Dimensional Printing: Computational and Experimental Cases of Study

Determining the values of various properties for new bio-inks for 3D printing is a very important task in the design of new materials. For this purpose, a large number of experimental works have been consulted, and a database with more than 1200 bioprinting tests has been created. These tests cover different combinations of conditions in terms of print pressure, temperature, and needle values, for example. These data are difficult to deal with in terms of determining combinations of conditions to optimize the tests and analyze new options. The best model demonstrated a specificity (Sp) of 88.4% and a sensitivity (Sn) of 86.2% in the training series while achieving an Sp of 85.9% and an Sn of 80.3% in the external validation series. This model utilizes operators based on perturbation theory to analyze the complexity of the data. For comparative purposes, neural networks have been used, and very similar results have been obtained. The developed tool could easily be applied to predict the properties of bioprinting assays in silico. These findings could significantly improve the efficiency and accuracy of predictive models in bioprinting without resorting to trial-and-error tests, thereby saving time and funds. Ultimately, this tool may help pave the way for advances in personalized medicine and tissue engineering.

Cutting-edge 3D printing in immunosensor design for early cancer detection

Cancer is a major cause of death globally, and early detection is a key to improving outcomes. Traditional diagnostic methods have limitations such as being invasive and lacking sensitivity. Immunosensors, which detect cancer biomarkers using antibodies, offer a solution with high sensitivity and selectivity. When combined with 3D printing, these immunosensors can be customized to detect specific cancer markers, creating rapid, cost-effective, and scalable diagnostic tools. The article reviews the principles behind immunosensors, different 3D fabrication methods such as Fused Deposition Modeling (FDM) and Stereolithography (SLA), and discusses how functionalization strategies, such as surface modifications, can enhance the sensitivity of these devices. The integration of 3D printing allows for the creation of complex sensor structures, offering advantages such as customization, rapid prototyping, and multi-material printing. These advancements make immunosensors arrays highly promising for early cancer detection, tumor profiling, and personalized medicine. The article also explores challenges like scalability, material biocompatibility, and the need for clinical validation. Future perspectives suggest the potential of integrating nanomaterials, multiplexed detection, and wearable technology to further improve the performance and accessibility of these diagnostic tools.

Osteoradionecrosis of the Jaws and Management Strategies

Background

Osteoradionecrosis of the jaws (ORNJ) is a severe complication arising from radiotherapy for head and neck cancers. It results from irreversible damage to osteocytes, leading to nonhealing of exposed bone. The condition can cause substantial pain, swelling, trismus, and in severe cases, pathological fractures of the jaw, substantially impacting the patient's quality of life and increasing morbidity.

Aims

This review aims to describe the pathophysiology of ORNJ, evaluate current management strategies, and explore emerging therapies to provide a comprehensive understanding of this condition.

Methods

A comprehensive literature review was conducted to describe the pathophysiology, clinical presentation, and treatment of ORNJ.

Results

The pathophysiology of ORNJ involves multiple theories, including radiation‐induced fibrosis and the “hypoxia, hypocellular, and hypovascular” model. Management strategies include surgical debridement, hyperbaric oxygen therapy (HBOT), and emerging biological approaches such as tissue engineering and platelet‐rich plasma (PRP), which are all discussed.

Discussion

Radiotherapy significantly impairs wound healing, leading to chronic fibrosis and tissue necrosis. Although ORNJ is uncommon, its impact on patients is substantial. Current treatments offer limited success, necessitating a multidisciplinary approach and ongoing research into innovative therapies. Emerging treatments, including tissue engineering and PRP, offer potential but require further research.

Conclusion

ORNJ remains a challenging condition with substantial patient morbidity. Understanding its pathophysiology is crucial for patient education, early detection and developing effective management strategies.

Hybrid-integrated devices for mimicking malignant brain tumors ("tumor-on-a-chip") for in vitro development of targeted drug delivery and personalized therapy approaches

Acute and requiring attention problem of oncotheranostics is a necessity for the urgent development of operative and precise diagnostics methods, followed by efficient therapy, to significantly reduce disability and mortality of citizens. A perspective way to achieve efficient personalized treatment is to use methods for operative evaluation of the individual drug load, properties of specific tumors and the effectiveness of selected therapy, and other actual features of pathology. Among the vast diversity of tumor types-brain tumors are the most invasive and malignant in humans with poor survival after diagnosis. Among brain tumors glioblastoma shows exceptionally high mortality. More studies are urgently needed to understand the risk factors and improve therapy approaches. One of the actively developing approaches is the tumor-on-a-chip (ToC) concept. This review examines the achievements of recent years in the field of ToC system developments. The basics of microfluidic chips technologies are considered in the context of their applications in solving oncological problems. Then the basic principles of tumors cultivation are considered to evaluate the main challengers in implementation of microfluidic devices, for growing cell cultures and possibilities of their treatment and observation. The main achievements in the culture types diversity approaches and their advantages are being analyzed. The modeling of angiogenesis and blood-brain barrier (BBB) on a chip, being a principally important elements of the life system, were considered in detail. The most interesting examples and achievements in the field of tumor-on-a-chip developments have been presented.

3D printing and computer-aided design techniques for drug delivery scaffolds in tissue engineering

INTRODUCTION

The challenge in tissue engineering lies in replicating the intricate structure of the native extracellular matrix. Recent advancements in AM, notably 3D printing, offer unprecedented capabilities to tailor scaffolds precisely, controlling properties like structure and bioactivity. CAD tools complement this by facilitating design using patient-specific data.

AREA’S COVERED

This review introduces additive manufacturing (AM) and computer-aided design (CAD) as pivotal tools in advancing tissue engineering, particularly cartilage regeneration. This article explores various materials utilized in AM, focusing on polymers and hydrogels for their advantageous properties in tissue engineering applications. Integrating bioactive molecules, including growth factors, into scaffolds to promote tissue regeneration is discussed alongside strategies involving different cell sources, such as stem cells, to enhance tissue development within scaffold matrices.

EXPERT OPINION

Applications of AM and CAD in addressing specific challenges like osteochondral defects and osteoarthritis in cartilage tissue engineering are highlighted. This review consolidates current research findings, offering expert insights into the evolving landscape of AM and CAD technologies in advancing tissue engineering, particularly in cartilage regeneration.

Advancements of Biomacromolecular Hydrogel Applications in Food Nutrition and Health

Hydrogels exhibit remarkable degradability, biocompatibility and functionality, which position them as highly promising materials for applications within the food and pharmaceutical industries. Although many relevant studies on hydrogels have been reported in the chemical industry, materials, and other fields, there have been few reviews on their potential applications in food nutrition and human health. This study aims to address this gap by reviewing the functional properties of hydrogels and assessing their value in terms of food nutrition and human health. The use of hydrogels in preserving bioactive ingredients, food packaging and food distribution is delved into specifically in this review. Hydrogels can serve as cutting-edge materials for food packaging and delivery, ensuring the preservation of nutritional activity within food products, facilitating targeted delivery of bioactive compounds and regulating the digestion and absorption processes in the human body, thereby promoting human health. Moreover, hydrogels find applications in in vitro cell and tissue culture, human tissue repair, as well as chronic disease prevention and treatment. These broad applications have attracted great attention in the fields of human food nutrition and health. Ultimately, this paper serves as a valuable reference for further utilization and exploration of hydrogels in these respective fields.

Biomimicking trilayer scaffolds with controlled estradiol release for uterine tissue regeneration

Scaffold-based tissue engineering provides an efficient approach for repairing uterine tissue defects and restoring fertility. In the current study, a novel trilayer tissue engineering scaffold with high similarity to the uterine tissue in structure was designed and fabricated via 4D printing, electrospinning and 3D bioprinting for uterine regeneration. Highly stretchable poly(l-lactide-co-trimethylene carbonate) (PLLA-co-TMC, "PTMC" in short)/thermoplastic polyurethane (TPU) polymer blend scaffolds were firstly made via 4D printing. To improve the biocompatibility, porous poly(lactic acid-co-glycolic acid) (PLGA)/gelatin methacryloyl (GelMA) fibers incorporated with polydopamine (PDA) particles were produced on PTMC/TPU scaffolds via electrospinning. Importantly, estradiol (E2) was encapsulated in PDA particles. The bilayer scaffolds thus produced could provide controlled and sustained release of E2. Subsequently, bone marrow derived mesenchymal stem cells (BMSCs) were mixed with gelatin methacryloyl (GelMA)-based inks and the formulated bioinks were used to fabricate a cell-laden hydrogel layer on the bilayer scaffolds via 3D bioprinting, forming ultimately biomimicking trilayer scaffolds for uterine tissue regeneration. The trilayer tissue engineering scaffolds thus formed exhibited a shape morphing ability by transforming from the planar shape to tubular structures when immersed in the culture medium at 37°C. The trilayer tissue engineering scaffolds under development would provide new insights for uterine tissue regeneration.

Advanced tumor organoid bioprinting strategy for oncology research

Bioprinting is a groundbreaking technology that enables precise distribution of cell-containing bioinks to construct organoid models that accurately reflect the characteristics of tumors in vivo. By incorporating different types of tumor cells into the bioink, the heterogeneity of tumors can be replicated, enabling studies to simulate real-life situations closely. Precise reproduction of the arrangement and interactions of tumor cells using bioprinting methods provides a more realistic representation of the tumor microenvironment. By mimicking the complexity of the tumor microenvironment, the growth patterns and diffusion of tumors can be demonstrated. This approach can also be used to evaluate the response of tumors to drugs, including drug permeability and cytotoxicity, and other characteristics. Therefore, organoid models can provide a more accurate oncology research and treatment simulation platform. This review summarizes the latest advancements in bioprinting to construct tumor organoid models. First, we describe the bioink used for tumor organoid model construction, followed by an introduction to various bioprinting methods for tumor model formation. Subsequently, we provide an overview of existing bioprinted tumor organoid models.

Bioprinting of Cells, Organoids and Organs-on-a-Chip Together with Hydrogels Improves Structural and Mechanical Cues

The 3D bioprinting technique has made enormous progress in tissue engineering, regenerative medicine and research into diseases such as cancer. Apart from individual cells, a collection of cells, such as organoids, can be printed in combination with various hydrogels. It can be hypothesized that 3D bioprinting will even become a promising tool for mechanobiological analyses of cells, organoids and their matrix environments in highly defined and precisely structured 3D environments, in which the mechanical properties of the cell environment can be individually adjusted. Mechanical obstacles or bead markers can be integrated into bioprinted samples to analyze mechanical deformations and forces within these bioprinted constructs, such as 3D organoids, and to perform biophysical analysis in complex 3D systems, which are still not standard techniques. The review highlights the advances of 3D and 4D printing technologies in integrating mechanobiological cues so that the next step will be a detailed analysis of key future biophysical research directions in organoid generation for the development of disease model systems, tissue regeneration and drug testing from a biophysical perspective. Finally, the review highlights the combination of bioprinted hydrogels, such as pure natural or synthetic hydrogels and mixtures, with organoids, organoid-cell co-cultures, organ-on-a-chip systems and organoid-organ-on-a chip combinations and introduces the use of assembloids to determine the mutual interactions of different cell types and cell-matrix interferences in specific biological and mechanical environments.

Characterization and application of photocrosslinkable collagen maleate as bioink in extrusion-based 3D bioprinting

3D bioprinting, a significant advancement in biofabrication, is renowned for its precision in creating tissue constructs. Collagen, despite being a gold standard biomaterial, faces challenges in bioink formulations due to its unique physicochemical properties. This study introduces a novel, neutral-soluble, photocrosslinkable collagen maleate (ColME) that is ideal for 3D bioprinting. ColME was synthesized by chemically modifying bovine type I collagen with maleic anhydride, achieving a high substitution ratio that shifted the isoelectric point to enhance solubility in physiological pH environments. This modification was confirmed to preserve the collagen's triple-helix structure substantially. Bioprinting parameters for ColME were optimized, focusing on adjustments to the bioink concentration, extrusion pressure, nozzle speed, and temperature. Results demonstrated that lower temperatures and smaller nozzle sizes substantially improved the print quality of grid structures. Additionally, the application of intermittent photo-crosslinking facilitated the development of structurally robust 3D multilayered constructs, enabling the stable fabrication of complex tissues. Cell viability assays showed that encapsulated cells within the ColME matrix maintained high viability after printing. When compared to methacrylated gelatin, ColME exhibited superior mechanical strength, resistance to enzymatic digestion, and overall printability, positioning it as an outstanding bioink for the creation of durable, bioactive 3D tissues.

Recent Advances in Hydrogel-Based Biosensors for Cancer Detection

Early cancer detection is crucial for effective treatment, but current methods have limitations. Novel biomaterials, such as hydrogels, offer promising alternatives for developing biosensors for cancer detection. Hydrogels are three-dimensional and cross-linked networks of hydrophilic polymers that have properties similar to biological tissues. They can be combined with various biosensors to achieve high sensitivity, specificity, and stability. This review summarizes the recent advances in hydrogel-based biosensors for cancer detection, their synthesis, their applications, and their challenges. It also discusses the implications and future directions of this emerging field.

Methods to achieve tissue-mimetic physicochemical properties in hydrogels for regenerative medicine and tissue engineering

Hydrogels are water-swollen polymeric matrices with properties that are remarkably similar in function to the extracellular matrix. For example, the polymer matrix provides structural support and adhesion sites for cells in much of the same way as the fibers of the extracellular matrix. In addition, depending on the polymer used, bioactive sites on the polymer may provide signals to initiate certain cell behavior. However, despite their potential as biomaterials for tissue engineering and regenerative medicine applications, fabricating hydrogels that truly mimic the physicochemical properties of the extracellular matrix to physiologically-relevant values is a challenge. Recent efforts in the field have sought to improve the physicochemical properties of hydrogels using advanced materials science and engineering methods. In this review, we highlight some of the most promising methods, including crosslinking strategies and manufacturing approaches such as 3D bioprinting and granular hydrogels. We also provide a brief perspective on the future outlook of this field and how these methods may lead to the clinical translation of hydrogel biomaterials for tissue engineering and regenerative medicine applications.

Laser-Based Selective Material Processing for Next-Generation Additive Manufacturing

The connection between laser-based material processing and additive manufacturing is quite deeply rooted. In fact, the spark that started the field of additive manufacturing is the idea that two intersecting laser beams can selectively solidify a vat of resin. Ever since, laser has been accompanying the field of additive manufacturing, with its repertoire expanded from processing only photopolymer resin to virtually any material, allowing liberating customizability. As a result, additive manufacturing is expected to take an even more prominent role in the global supply chain in years to come. Herein, an overview of laser-based selective material processing is presented from various aspects: the physics of laser-material interactions, the materials currently used in additive manufacturing processes, the system configurations that enable laser-based additive manufacturing, and various functional applications of next-generation additive manufacturing. Additionally, current challenges and prospects of laser-based additive manufacturing are discussed.

Engineering Considerations on Large-Scale Cultured Meat Production

In recent decades, cultured meat has received considerable interest as a sustainable alternative to traditional meat products, showing promise for addressing the inherent problems associated with conventional meat production. However, current limitations on the scalability of production and extremely high production costs have prevented their widespread adoption. Therefore, it is important to develop novel engineering strategies to overcome the current limitations in large-scale cultured meat production. Such engineering considerations have the potential for advancements in cultured meat production by providing innovative and effective solutions to the prevailing challenges. In this review, we discuss how engineering strategies have been utilized to advance cultured meat technology by categorizing the production processes of cultured meat into three distinct steps: (1) cell preparation; (2) cultured meat fabrication; and (3) cultured meat maturation. For each step, we provide a comprehensive discussion of the recent progress and its implications. In particular, we focused on the engineering considerations involved in each step of cultured meat production, with specific emphasis on large-scale production.

Engineering biomaterials by inkjet printing of hydrogels with functional particulates

Hydrogels with particulates, including proteins, drugs, nanoparticles, and cells, enable the development of new and innovative biomaterials. Precise control of the spatial distribution of these particulates is crucial to produce advanced biomaterials. Thus, there is a high demand for manufacturing methods for particle-laden hydrogels. In this context, 3D printing of hydrogels is emerging as a promising method to create numerous innovative biomaterials. Among the 3D printing methods, inkjet printing, so-called drop-on-demand (DOD) printing, stands out for its ability to construct biomaterials with superior spatial resolutions. However, its printing processes are still designed by trial and error due to a limited understanding of the ink behavior during the printing processes. This review discusses the current understanding of transport processes and hydrogel behaviors during inkjet printing for particulate-laden hydrogels. Specifically, we review the transport processes of water and particulates within hydrogel during ink formulation, jetting, and curing. Additionally, we examine current inkjet printing applications in fabricating engineered tissues, drug delivery devices, and advanced bioelectronics components. Finally, the challenges and opportunities for next-generation inkjet printing are also discussed.

Graphical Abstract

Advances in Cell-Rich Inks for Biofabricating Living Architectures

Advancing biofabrication toward manufacturing living constructs with well-defined architectures and increasingly biologically relevant cell densities is highly desired to mimic the biofunctionality of native human tissues. The formulation of tissue-like, cell-dense inks for biofabrication remains, however, challenging at various levels of the bioprinting process. Promising advances have been made toward this goal, achieving relatively high cell densities that surpass those found in conventional platforms, pushing the current boundaries closer to achieving tissue-like cell densities. On this focus, herein the overarching challenges in the bioprocessing of cell-rich living inks into clinically grade engineered tissues are discussed, as well as the most recent advances in cell-rich living ink formulations and their processing technologies are highlighted. Additionally, an overview of the foreseen developments in the field is provided and critically discussed.

Recent Advances in Implantable 3D-Printed Scaffolds for Repair of Spinal Cord Injury

Spinal cord injury (SCI) is an important factor in sensory and motor disorders that affects thousands of people every year. Currently, despite successes in basic science and clinical research, there are few effective methods in the treatment of chronic and acute spinal cord injuries. In the last decade, the use of 3D printed scaffolds in the treatment of SCI had satisfactory and promising results. By providing a microenvironment around the injury site and in combination with growth factors or cells, 3D printed scaffolds help in axon regeneration as well as neural recovery after SCI. Here, we provide an overview of tissue engineering, 3D printing scaffolds, the different polymers used and their characterization methods. This review highlights the recent encouraging applications of 3D printing scaffolds in developing the novel SCI therapy.

Superimposed Electric Field Enhanced Electrospray for High-Throughput and Consistent Cell Encapsulation

Cell encapsulation technology, crucial for advanced biomedical applications, faces challenges in existing microfluidic and electrospray methods. Microfluidic techniques, while precise, can damage vulnerable cells, and conventional electrospray methods often encounter instability and capsule breakage during high-throughput encapsulation. Inspired by the transformation of the working state from unstable dripping to stable jetting triggered by local electric potential, this study introduces a superimposed electric field (SEF)-enhanced electrospray method for cell encapsulation, with improved stability and biocompatibility. Utilizing stiffness theory, the stability of the electrospray, whose stiffness is five times stronger under conical confinement, is quantitatively analyzed. The SEF technique enables rapid, continuous production of ≈300 core-shell capsules per second in an aqueous environment, significantly improving cell encapsulation efficiency. This method demonstrates remarkable potential as exemplified in two key applications: (1) a 92-fold increase in human-derived induced pluripotent stem cells (iPSCs) expansion over 10 d, outperforming traditional 2D cultures in both growth rate and pluripotency maintenance, and (2) the development of liver capsules for steatosis modeling, exhibiting normal function and biomimetic lipid accumulation. The SEF-enhanced electrospray method presents a significant advancement in cell encapsulation technology. It offers a more efficient, stable, and biocompatible approach for clinical transplantation, drug screening, and cell therapy.

Towards Stem Cell Therapy for Critical-Sized Segmental Bone Defects: Current Trends and Challenges on the Path to Clinical Translation

The management and reconstruction of critical-sized segmental bone defects remain a major clinical challenge for orthopaedic clinicians and surgeons. In particular, regenerative medicine approaches that involve incorporating stem cells within tissue engineering scaffolds have great promise for fracture management. This narrative review focuses on the primary components of bone tissue engineering-stem cells, scaffolds, the microenvironment, and vascularisation-addressing current advances and translational and regulatory challenges in the current landscape of stem cell therapy for critical-sized bone defects. To comprehensively explore this research area and offer insights for future treatment options in orthopaedic surgery, we have examined the latest developments and advancements in bone tissue engineering, focusing on those of clinical relevance in recent years. Finally, we present a forward-looking perspective on using stem cells in bone tissue engineering for critical-sized segmental bone defects.

Controlled oxygen delivery to power tissue regeneration

Oxygen plays a crucial role in human embryogenesis, homeostasis, and tissue regeneration. Emerging engineered regenerative solutions call for novel oxygen delivery systems. To become a reality, these systems must consider physiological processes, oxygen release mechanisms and the target application. In this review, we explore the biological relevance of oxygen at both a cellular and tissue level, and the importance of its controlled delivery via engineered biomaterials and devices. Recent advances and upcoming trends in the field are also discussed with a focus on tissue-engineered constructs that could meet metabolic demands to facilitate regeneration.

3D Bioprinting of Sugar Beet Pectin through Horseradish Peroxidase-Catalyzed Cross-Linking

Horseradish peroxidase (HRP)-mediated hydrogelation, caused by the cross-linking of phenolic groups in polymers in the presence of hydrogen peroxide (H2O2), is an effective route for bioink solidification in 3D bioprinting. Sugar beet pectin (SBP) naturally has cross-linkable phenols through the enzymatic reaction. Therefore, chemical modifications are not required, unlike the various polymers that have been used in the enzymatic cross-linking system. In this study, we report the application of SBP in extrusion-based bioprinting including HRP-mediated bioink solidification. In this system, H2O2 necessary for the solidification of inks is supplied in the gas phase. Cell-laden liver lobule-like constructs could be fabricated using bioinks consisting of 10 U/mL HRP, 4.0 and 6.0 w/v% SBP, and 6.0 × 106 cells/mL human hepatoblastoma (HepG2) cells exposed to air containing 16 ppm of H2O2 concurrently during printing and 10 min postprinting. The HepG2 cells enclosed in the printed constructs maintained their viability, metabolic activity, and hepatic functions from day 1 to day 7 of the culture, which indicates the cytocompatibility of this system. Taken together, this result demonstrates the potential of SBP and HRP cross-linking systems for 3D bioprinting, which can be applied in tissue engineering applications.

Three-Dimensional Bioprinting of GelMA Hydrogels with Culture Medium: Balancing Printability, Rheology and Cell Viability for Tissue Regeneration

Three-dimensional extrusion bioprinting technology aims to become a fundamental tool for tissue regeneration using cell-loaded hydrogels. These biomaterials must have highly specific mechanical and biological properties that allow them to generate biosimilar structures by successive layering of material while maintaining cell viability. The rheological properties of hydrogels used as bioinks are critical to their printability. Correct printability of hydrogels allows the replication of biomimetic structures, which are of great use in medicine, tissue engineering and other fields of study that require the three-dimensional replication of different tissues. When bioprinting cell-loaded hydrogels, a small amount of culture medium can be added to ensure adequate survival, which can modify the rheological properties of the hydrogels. GelMA is a hydrogel used in bioprinting, with very interesting properties and rheological parameters that have been studied and defined for its basic formulation. However, the changes that occur in its rheological parameters and therefore in its printability, when it is mixed with the culture medium necessary to house the cells inside, are unknown. Therefore, in this work, a comparative study of GelMA 100% and GelMA in the proportions 3:1 (GelMA 75%) and 1:1 (GelMA 50%) with culture medium was carried out to determine the printability of the gel (using a device of our own invention), its main rheological parameters and its toxicity after the addition of the medium and to observe whether significant differences in cell viability occur. This raises the possibility of its use in regenerative medicine using a 3D extrusion bioprinter.

Organoid bioinks: construction and application

Organoids have emerged as crucial platforms in tissue engineering and regenerative medicine but confront challenges in faithfully mimicking native tissue structures and functions. Bioprinting technologies offer a significant advancement, especially when combined with organoid bioinks-engineered formulations designed to encapsulate both the architectural and functional elements of specific tissues. This review provides a rigorous, focused examination of the evolution and impact of organoid bioprinting. It emphasizes the role of organoid bioinks that integrate key cellular components and microenvironmental cues to more accurately replicate native tissue complexity. Furthermore, this review anticipates a transformative landscape invigorated by the integration of artificial intelligence with bioprinting techniques. Such fusion promises to refine organoid bioink formulations and optimize bioprinting parameters, thus catalyzing unprecedented advancements in regenerative medicine. In summary, this review accentuates the pivotal role and transformative potential of organoid bioinks and bioprinting in advancing regenerative therapies, deepening our understanding of organ development, and clarifying disease mechanisms.

Janus hydrogels: merging boundaries in tissue engineering for enhanced biomaterials and regenerative therapies

In recent years, the design and synthesis of Janus hydrogels have witnessed a thriving development, overcoming the limitations of single-performance materials and expanding their potential applications in tissue engineering and regenerative medicine. Janus hydrogels, with their exceptional mechanical properties and excellent biocompatibility, have emerged as promising candidates for various biomedical applications, including tissue engineering and regenerative therapies. In this review, we present the latest progress in the synthesis of Janus hydrogels using commonly employed preparation methods. We elucidate the surface and interface interactions of these hydrogels and discuss the enhanced properties bestowed by the unique "Janus" structure in biomaterials. Additionally, we explore the applications of Janus hydrogels in facilitating regenerative therapies, such as drug delivery, wound healing, tissue engineering, and biosensing. Furthermore, we analyze the challenges and future trends associated with the utilization of Janus hydrogels in biomedical applications.

Bioprinting Soft 3D Models of Hematopoiesis using Natural Silk Fibroin-Based Bioink Efficiently Supports Platelet Differentiation

Hematopoietic stem and progenitor cells (HSPCs) continuously generate platelets throughout one's life. Inherited Platelet Disorders affect ≈ 3 million individuals worldwide and are characterized by defects in platelet formation or function. A critical challenge in the identification of these diseases lies in the absence of models that facilitate the study of hematopoiesis ex vivo. Here, a silk fibroin-based bioink is developed and designed for 3D bioprinting. This bioink replicates a soft and biomimetic environment, enabling the controlled differentiation of HSPCs into platelets. The formulation consisting of silk fibroin, gelatin, and alginate is fine-tuned to obtain a viscoelastic, shear-thinning, thixotropic bioink with the remarkable ability to rapidly recover after bioprinting and provide structural integrity and mechanical stability over long-term culture. Optical transparency allowed for high-resolution imaging of platelet generation, while the incorporation of enzymatic sensors allowed quantitative analysis of glycolytic metabolism during differentiation that is represented through measurable color changes. Bioprinting patient samples revealed a decrease in metabolic activity and platelet production in Inherited Platelet Disorders. These discoveries are instrumental in establishing reference ranges for classification and automating the assessment of treatment responses. This model has far-reaching implications for application in the research of blood-related diseases, prioritizing drug development strategies, and tailoring personalized therapies.

Artificial Cells and HepG2 Cells in 3D-Bioprinted Arrangements

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

In Vitro and In Vivo Evaluation of 3D Printed Poly(Ethylene Glycol) Dimethacrylate-Based Photocurable Hydrogel Platform for Bone Tissue Engineering

This study focuses to develop a unique hybrid hydrogel bioink formulation that incorporates poly(ethylene glycol) dimethacrylate (PEGDMA), gelatin (Gel), and methylcellulose (MC). This formulation achieves the necessary viscosity for extrusion-based three-dimensional (3D) printing of scaffolds intended for bone regeneration. After thorough optimization of the hybrid bioink system with Gel, three distinct scaffold groups are investigated in vitro: 0%, 3%, and 6% (w/v) Gel. These scaffold groups are examined for their morphology, mechanical strength, biodegradation, in vitro cell proliferation and differentiation, and in vivo bone formation using a rat cranial defect model. Among these scaffold compositions, the 3% Gel scaffold exhibits the most favorable characteristics, prompting further evaluation as a rat mesenchymal stem cell (rMSC) carrier in a critical-size cranial defect within a Lewis rat model. The compressive strength of all three scaffold groups range between 1 and 2 MPa. Notably, the inclusion of Gel in the scaffolds leads to enhanced bioactivity and cell adhesion. The Gel-containing scaffolds notably amplify osteogenic differentiation, as evidenced by alkaline phosphatase (ALP) and Western blot analyses. The in vivo results, as depicted by microcomputed tomography, showcase augmented osteogenesis within cell-seeded scaffolds, thus validating this innovative PEGDMA-based scaffold system as a promising candidate for cranial bone defect healing.

Highly oriented hydrogels for tissue regeneration: design strategies, cellular mechanisms, and biomedical applications

Many human tissues exhibit a highly oriented architecture that confers them with distinct mechanical properties, enabling adaptation to diverse and challenging environments. Hydrogels, with their water-rich "soft and wet" structure, have emerged as promising biomimetic materials in tissue engineering for repairing and replacing damaged tissues and organs. Highly oriented hydrogels can especially emulate the structural orientation found in human tissue, exhibiting unique physiological functions and properties absent in traditional homogeneous isotropic hydrogels. The design and preparation of highly oriented hydrogels involve strategies like including hydrogels with highly oriented nanofillers, polymer-chain networks, void channels, and microfabricated structures. Understanding the specific mechanism of action of how these highly oriented hydrogels affect cell behavior and their biological applications for repairing highly oriented tissues such as the cornea, skin, skeletal muscle, tendon, ligament, cartilage, bone, blood vessels, heart, etc., requires further exploration and generalization. Therefore, this review aims to fill that gap by focusing on the design strategy of highly oriented hydrogels and their application in the field of tissue engineering. Furthermore, we provide a detailed discussion on the application of highly oriented hydrogels in various tissues and organs and the mechanisms through which highly oriented structures influence cell behavior.

The application of a 4D-printed chitosan-based stem cell carrier for the repair of corneal alkali burns

BACKGROUND

Corneal alkali burns can lead to ulceration, perforation, and even corneal blindness due to epithelial defects and extensive cell necrosis, resulting in poor healing outcomes. Previous studies have found that chitosan-based in situ hydrogel loaded with limbal epithelium stem cells (LESCs) has a certain reparative effect on corneal alkali burns. However, the inconsistent pore sizes of the carriers and low cell loading rates have resulted in suboptimal repair outcomes. In this study, 4D bioprinting technology was used to prepare a chitosan-based thermosensitive gel carrier (4D-CTH) with uniform pore size and adjustable shape to improve the transfer capacity of LESCs.

METHODS

Prepare solutions of chitosan acetate, carboxymethyl chitosan, and β-glycerophosphate sodium at specific concentrations, and mix them in certain proportions to create a pore-size uniform scaffold using 4D bioprinting technology. Extract and culture rat LESCs (rLESCs) in vitro, perform immunofluorescence experiments to observe the positivity rate of deltaNp63 cells for cell identification. Conduct a series of experiments to validate the cell compatibility of 4D-CTH, including CCK-8 assay to assess cell toxicity, scratch assay to evaluate the effect of 4D-CTH on rLESCs migration, and Calcein-AM/PI cell staining experiment to examine the impact of 4D-CTH on rLESCs proliferation and morphology. Establish a severe alkali burn model in rat corneas, transplant rLESCs onto the injured cornea using 4D-CTH, periodically observe corneal opacity and neovascularization using a slit lamp, and evaluate epithelial healing by fluorescein sodium staining. Assess the therapeutic effect 4D-CTH-loaded rLESCs on corneal alkali burn through histological evaluation of corneal tissue paraffin sections stained with hematoxylin and eosin, as well as immunofluorescence staining of frozen sections.

RESULTS

Using the 4D-CTH, rLESCs were transferred to the alkali burn wounds of rats. Compared with the traditional treatment group (chitosan in situ hydrogel encapsulating rLESCs), the 4D-CTH-rLESC group had significantly higher repair efficiency of corneal injury, such as lower corneal opacity score (1.2 ± 0.4472 vs 0.4 ± 0.5477, p < 0.05) and neovascularization score (5.5 ± 1.118 vs 2.6 ± 0.9618, p < 0.01), and significantly higher corneal epithelial wound healing rate (72.09 ± 3.568% vs 86.60 ± 5.004%, p < 0.01).

CONCLUSION

In summary, the corneas of the 4D-CTH-rLESC treatment group were similar to the normal corneas and had a complete corneal structure. These findings suggested that LESCs encapsulated by 4D-CTH significantly accelerated corneal wound healing after alkali burn and can be considered as a rapid and effective method for treating epithelial defects.

Recent advances in composite hydrogels: synthesis, classification, and application in the treatment of bone defects

Bone defects are often difficult to treat due to their complexity and specificity, and therefore pose a serious threat to human life and health. Currently, the clinical treatment of bone defects is mainly surgical. However, this treatment is often more harmful to patients and there is a potential risk of rejection and infection. Hydrogels have a unique three-dimensional structure that can accommodate a variety of materials, including particles, polymers and small molecules, making them ideal for treating bone defects. Therefore, emerging composite hydrogels are considered one of the most promising candidates for the treatment of bone defects. This review describes the use of different types of composite hydrogel in the treatment of bone defects. We present the basic concepts of hydrogels, different preparation techniques (including chemical and physical crosslinking), and the clinical requirements for hydrogels used to treat bone defects. In addition, a review of numerous promising designs of different types of hydrogel doped with different materials (e.g., nanoparticles, polymers, carbon materials, drugs, and active factors) is also highlighted. Finally, the current challenges and prospects of composite hydrogels for the treatment of bone defects are presented. This review will stimulate research efforts in this field and promote the application of new methods and innovative ideas in the clinical field of composite hydrogels.

Recent Advancements of Bioinks for 3D Bioprinting of Human Tissues and Organs

3D bioprinting is recognized as a promising biomanufacturing technology that enables the reproducible and high-throughput production of tissues and organs through the deposition of different bioinks. Especially, bioinks based on loaded cells allow for immediate cellularity upon printing, providing opportunities for enhanced cell differentiation for organ manufacturing and regeneration. Thus, extensive applications have been found in the field of tissue engineering. The performance of the bioinks determines the functionality of the entire printed construct throughout the bioprinting process. It is generally expected that bioinks should support the encapsulated cells to achieve their respective cellular functions and withstand normal physiological pressure exerted on the printed constructs. The bioinks should also exhibit a suitable printability for precise deposition of the constructs. These characteristics are essential for the functional development of tissues and organs in bioprinting and are often achieved through the combination of different biomaterials. In this review, we have discussed the cutting-edge outstanding performance of different bioinks for printing various human tissues and organs in recent years. We have also examined the current status of 3D bioprinting and discussed its future prospects in relieving or curing human health problems.

Proteolytic remodeling of 3D bioprinted tumor microenvironments

In native tissue, remodeling of the pericellular space is essential for cellular activities and is mediated by tightly regulated proteases. Protease activity is dysregulated in many diseases, including many forms of cancer. Increased proteolytic activity is directly linked to tumor invasion into stroma, metastasis, and angiogenesis as well as all other hallmarks of cancer. Here we show a strategy for 3D bioprinting of breast cancer models using well-defined protease degradable hydrogels that can facilitate exploration of the multifaceted roles of proteolytic extracellular matrix remodeling in tumor progression. We designed a set of bicyclo[6.1.0]nonyne functionalized hyaluronan (HA)-based bioinks cross-linked by azide-modified poly(ethylene glycol) (PEG) or matrix metalloproteinase (MMP) degradable azide-functionalized peptides. Bioprinted structures combining PEG and peptide-based hydrogels were proteolytically degraded with spatial selectivity, leaving non-degradable features intact. Bioprinting of tumor-mimicking microenvironments using bioinks comprising human breast cancer cells (MCF-7) and fibroblast in hydrogels with different susceptibilities to proteolytic degradation shows that MCF-7 proliferation and spheroid size were significantly increased in protease degradable hydrogel compartments, but only in the presence of fibroblasts. In the absence of fibroblasts in the stromal compartment, cancer cell proliferation was reduced and did not differ between degradable and nondegradable hydrogels. The interactions between spatially separated fibroblasts and MCF-7 cells consequently resulted in protease-mediated remodeling of the bioprinted structures and a significant increase in cancer cell spheroid size, highlighting the close interplay between cancer cells and stromal cells in the tumor microenvironment and the influence of proteases in tumor progression.

Injectable cell-laden silk acid hydrogel

This study presents an injectable cell-laden hydrogel system based on silk acid, a carboxylated derivative of natural silk fibroin, which exhibits promising applications in biomedicine. The hydrogel is produced under physiological conditions (37 °C and pH 7.4) via physical crosslinking. Notably, the hydrogel demonstrates remarkable cytocompatibility, enabling efficient cell encapsulation, and exhibits good injectability. These promising results strongly indicate the potential of silk acid hydrogel for transformative applications, including 3D cell culture, targeted cell delivery, and tissue engineering.

Polysaccharide-based hydrogels for medical devices, implants and tissue engineering: A review

Hydrogels are highly biocompatible biomaterials composed of crosslinked three-dimensional networks of hydrophilic polymers. Owing to their natural origin, polysaccharide-based hydrogels (PBHs) possess low toxicity, high biocompatibility and demonstrate in vivo biodegradability, making them great candidates for use in various biomedical devices, implants, and tissue engineering. In addition, many polysaccharides also show additional biological activities such as antimicrobial, anticoagulant, antioxidant, immunomodulatory, hemostatic, and anti-inflammatory, which can provide additional therapeutic benefits. The porous nature of PBHs allows for the immobilization of antibodies, aptamers, enzymes and other molecules on their surface, or within their matrix, potentiating their use in biosensor devices. Specific polysaccharides can be used to produce transparent hydrogels, which have been used widely to fabricate ocular implants. The ability of PBHs to encapsulate drugs and other actives has been utilized for making neural implants and coatings for cardiovascular devices (stents, pacemakers and venous catheters) and urinary catheters. Their high water-absorption capacity has been exploited to make superabsorbent diapers and sanitary napkins. The barrier property and mechanical strength of PBHs has been used to develop gels and films as anti-adhesive formulations for the prevention of post-operative adhesion. Finally, by virtue of their ability to mimic various body tissues, they have been explored as scaffolds and bio-inks for tissue engineering of a wide variety of organs. These applications have been described in detail, in this review.

NIR light-facilitated bone tissue engineering

In the last decades, near-infrared (NIR) light has attracted considerable attention due to its unique properties and numerous potential applications in bioimaging and disease treatment. Bone tissue engineering for bone regeneration with the help of biomaterials is currently an effective means of treating bone defects. As a controlled light source with deeper tissue penetration, NIR light can provide real-time feedback of key information on bone regeneration in vivo utilizing fluorescence imaging and be used for bone disease treatment. This review provides a comprehensive overview of NIR light-facilitated bone tissue engineering, from the introduction of NIR probes as well as NIR light-responsive materials, and the visualization of bone regeneration to the treatment of bone-related diseases. Furthermore, the existing challenges and future development directions of NIR light-based bone tissue engineering are also discussed. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement.

Photocuring 3D printing technology as an advanced tool for promoting angiogenesis in hypoxia-related diseases

Three-dimensional (3D) bioprinting has emerged as a promising strategy for fabricating complex tissue analogs with intricate architectures, such as vascular networks. Achieving this necessitates bioink formulations that possess highly printable properties and provide a cell-friendly microenvironment mimicking the native extracellular matrix. Rapid advancements in printing techniques continue to expand the capabilities of researchers, enabling them to overcome existing biological barriers. This review offers a comprehensive examination of ultraviolet-based 3D bioprinting, renowned for its exceptional precision compared to other techniques, and explores its applications in inducing angiogenesis across diverse tissue models related to hypoxia. The high-precision and rapid photocuring capabilities of 3D bioprinting are essential for accurately replicating the intricate complexity of vascular networks and extending the diffusion limits for nutrients and gases. Addressing the lack of vascular structure is crucial in hypoxia-related diseases, as it can significantly improve oxygen delivery and overall tissue health. Consequently, high-resolution 3D bioprinting facilitates the creation of vascular structures within three-dimensional engineered tissues, offering a potential solution for addressing hypoxia-related diseases. Emphasis is placed on fundamental components essential for successful 3D bioprinting, including cell types, bioink compositions, and growth factors highlighted in recent studies. The insights provided in this review underscore the promising prospects of leveraging 3D printing technologies for addressing hypoxia-related diseases through the stimulation of angiogenesis, complementing the therapeutic efficacy of cell therapy.

Injectable smart stimuli-responsive hydrogels: pioneering advancements in biomedical applications

Hydrogels have established their significance as prominent biomaterials within the realm of biomedical research. However, injectable hydrogels have garnered greater attention compared with their conventional counterparts due to their excellent minimally invasive nature and adaptive behavior post-injection. With the rapid advancement of emerging chemistry and deepened understanding of biological processes, contemporary injectable hydrogels have been endowed with an "intelligent" capacity to respond to various endogenous/exogenous stimuli (such as temperature, pH, light and magnetic field). This innovation has spearheaded revolutionary transformations across fields such as tissue engineering repair, controlled drug delivery, disease-responsive therapies, and beyond. In this review, we comprehensively expound upon the raw materials (including natural and synthetic materials) and injectable principles of these advanced hydrogels, concurrently providing a detailed discussion of the prevalent strategies for conferring stimulus responsiveness. Finally, we elucidate the latest applications of these injectable "smart" stimuli-responsive hydrogels in the biomedical domain, offering insights into their prospects.

Gelation of Uniform Interfacial Diffusant in Embedded 3D Printing

While the human body has many different examples of perfusable structures with complex geometries, biofabrication methods to replicate this complexity are still lacking. Specifically, the fabrication of self-supporting, branched networks with multiple channel diameters is particularly challenging. Here, we present the Gelation of Uniform Interfacial Diffusant in Embedded 3D Printing (GUIDE-3DP) approach for constructing perfusable networks of interconnected channels with precise control over branching geometries and vessel sizes. To achieve user-specified channel dimensions, this technique leverages the predictable diffusion of crosslinking reaction-initiators released from sacrificial inks printed within a hydrogel precursor. We demonstrate the versatility of GUIDE-3DP to be adapted for use with diverse physicochemical crosslinking mechanisms by designing seven printable material systems. Importantly, GUIDE-3DP allows for the independent tunability of both the inner and outer diameters of the printed channels and the ability to fabricate seamless junctions at branch points. This 3D bioprinting platform is uniquely suited for fabricating lumenized structures with complex shapes characteristic of multiple hollow vessels throughout the body. As an exemplary application, we demonstrate the fabrication of vasculature-like networks lined with endothelial cells. GUIDE-3DP represents an important advance toward the fabrication of self-supporting, physiologically relevant networks with intricate and perfusable geometries.

Crosslinking strategies for biomimetic hydrogels in bone tissue engineering

Bone tissue engineering has become a popular area of study for making biomimetic hydrogels to treat bone diseases. In this work, we looked at biocompatible hydrogels that can be injected into bone defects that require the smallest possible surgery. Mineral ions can be attached to polymer chains to make useful hydrogels that help bones heal faster. These ions are very important for the balance of the body. In the chemically-triggered sector, advanced hydrogels cross-linked by different molecular agents have many advantages, such as being selective, able to form gels, and having mechanical properties that can be modified. In addition, different photo-initiators can be used to make photo cross linkable hydrogels react quickly and moderately under certain light bands. Enzyme-triggered hydrogels are another type of hydrogel that can be used to repair bone tissue because they are biocompatible and gel quickly. We also look at some of the important factors mentioned above that could change how well bone tissue engineering works as a therapy. Finally, this review summarizes the problems that still need to be solved to make clinically relevant hydrogels.