Organ Engineering Research Articles

Injectable and Self-Invigorating Hydrogel Applications in Dentistry and Periodontal Regeneration: A Literature Review.

Hydrogels are thought of as unique polymers utilized to build new materials, and two key factors that impact their features are their hydrophilicity and the degree of cross-linking of the polymer chains. An injectable hydrogel is based on the hypothesis that certain biomaterials can be injected into the body as a liquid and progressively solidify there. The scientific research community was intrigued and interested by its discovery. The hydrophilic polymers that are used to make hydrogels can typically be split into two groups: natural polymers derived from tissues or other sources of natural materials, and synthetic polymers produced by combining principles from organic chemistry and molecular engineering. A variety of organic and synthetic biomaterials, such as chitosan, collagen or gelatin, alginate, hyaluronic acid, heparin, chondroitin sulfate, polyethylene glycol, and polyvinyl alcohol, are used to generate injectable hydrogels. A promising biomaterial for the therapeutic injection of cells and bioactive chemicals for tissue regeneration in both dentistry and medicine, injectable hydrogels have recently attracted attention. Since injectable scaffolds can be implanted with less invasive surgery, their application is seen as a viable strategy in the regeneration of craniofacial tissue. Treatment for periodontitis that effectively promotes periodontal regeneration involves injecting a hydrogel that contains medications with simultaneous anti-inflammatory and tissue-regenerating capabilities. The advantages of injectable hydrogel for tissue engineering are enhanced by the capability of three-dimensional encapsulation. A material's injectability can be attributed to a variety of mechanisms. The hydrogels work well to reduce inflammation and promote periodontal tissue regeneration.

Metal-Organic Framework-Loaded Engineering DNAzyme for the Self-Powered Amplified Detection of MicroRNA.

DNAzyme shows great promise in designing a highly sensitive and specific sensing platform; however, the low cellular uptake efficiency, instability, and especially the insufficient cofactor supply inhibit the intracellular molecule sensor applications. Herein, we demonstrate a novel type of DNAzyme-based self-driven intracellular sensor for microRNA (miRNA) detection in living cells. The sensor consists of a metal-organic framework [zeolite imidazole framework (ZIF-8)] core loaded with a shell consisting of a rationally designed DNAzyme, where the substrate strand is modified with FAM and BHQ-1 nearby both the sides of the restriction site, respectively, while the enzyme strand consists of two separate strands with a complementary fragment to the substrate strand and the targeting miRNA, respectively. The ZIF-8 nanoparticles enable the efficient delivery of DNAzyme into the cell and protect the DNAzyme from degradation. The pH-responsive ZIF-8 degradation is accompanied with the release of the DNAzyme and Zn2+ cofactors, and the intracellular target miRNAs recognize and activate the DNAzyme driven by the Zn2+ cofactors to cleave the substrate strand, resulting in the release of the FAM-labeled shorter product strand and increased fluorescence for miRNA detection. The self-driven approach can be generally applied to various miRNAs' detection through DNAzyme engineering.

Microfluidic Formulation of Topological Hydrogels for Microtissue Engineering.

Microfluidics has recently emerged as a powerful tool in generation of submillimeter-sized cell aggregates capable of performing tissue-specific functions, so-called microtissues, for applications in drug testing, regenerative medicine, and cell therapies. In this work, we review the most recent advances in the field, with particular focus on the formulation of cell-encapsulating microgels of small "dimensionalities": "0D" (particles), "1D" (fibers), "2D" (sheets), etc., and with nontrivial internal topologies, typically consisting of multiple compartments loaded with different types of cells and/or biopolymers. Such structures, which we refer to as topological hydrogels or topological microgels (examples including core-shell or Janus microbeads and microfibers, hollow or porous microstructures, or granular hydrogels) can be precisely tailored with high reproducibility and throughput by using microfluidics and used to provide controlled "initial conditions" for cell proliferation and maturation into functional tissue-like microstructures. Microfluidic methods of formulation of topological biomaterials have enabled significant progress in engineering of miniature tissues and organs, such as pancreas, liver, muscle, bone, heart, neural tissue, or vasculature, as well as in fabrication of tailored microenvironments for stem-cell expansion and differentiation, or in cancer modeling, including generation of vascularized tumors for personalized drug testing. We review the available microfluidic fabrication methods by exploiting various cross-linking mechanisms and various routes toward compartmentalization and critically discuss the available tissue-specific applications. Finally, we list the remaining challenges such as simplification of the microfluidic workflow for its widespread use in biomedical research, bench-to-bedside transition including production upscaling, further in vivo validation, generation of more precise organ-like models, as well as incorporation of induced pluripotent stem cells as a step toward clinical applications.

Investigation of Mechanical Properties in PVA Hydrogels Due to Cation Interactions Described by Reactive Forcefield Based Molecular Dynamics Simulations

Hydrogels are cross-linked networks containing water and are widely used in multiple fields due to their intrinsic softness and diffusive properties. One field of particular interest is in medical devices and tissue and organ engineering. Poly(vinyl alcohol) (PVA) is one common hydrogel where its mechanical properties can be changed by using different salt solutions, making it more appropriate for certain applications, such as artificial neuron tissue. In this study, we used the ReaxFF reactive forcefield to investigate PVA in lithium and potassium chloride. It was hypothesized that lithium might promote a proton transfer from the PVA hydroxyl groups, therefore inhibiting the PVA from forming hydrogen bonds with itself, yielding a weaker PVA hydrogel. Conversely, potassium would not promote a proton transfer, instead getting inside the PVA structure, allowing a higher density of hydrogen bonds to form, creating a stronger PVA hydrogel. We were able to show a proton transfer was favorable in the lithium case and unfavorable in the potassium case. This explains the differences in mechanical properties shown in experimental results and provides atomistic detail to motivate tunable mechanical properties in PVA hydrogels in various salt solutions.

425.5: Achieving Localized Immunosuppression Through Ex Vivo Engineering of Organ Blood Vessels

Introduction: Classic immunosuppressants lead to systemic immune shutdown, though necessary to mediate transplant rejection, it may lead to various complications. To reduce off-target immunosuppression while retaining increased organ survival, we propose direct modification of the endothelium of vascular transplants ex vivo to achieve localized immunomodulation. The glycocalyx (eGcx), made up of membrane-bound glycoproteins, is of particular interest due to its ability to control cell to cell communication and the activation of immune response through cell recognition. During organ transplantation, inflammation and oxidative damage occurs and can lead to the shedding and damage of the eGcx layer; this has been linked to organ failure and rejection. We developed an enzymatic approach to modify the surface of the endothelium with immunosuppressive polymers to induce immunomodulatory effects locally. We tested the efficacy of this approach in murine transplants.Method: We developed a method using tissue transglutaminase (tTGase) as the surface immobilizing enzyme and polyglycerol polymers containing sialic acid or sulfate moieties that is compatible with UW organ preservation solution at 4°C. In vitro mechanistic studies were performed using EaHy.926 cells to replicate the endothelium and PBMCs and CAR-T cells were used to test immune cytotoxicity. In vivo efficacy of graft rejection was assessed through aortic vessel or renal grafts from BALB/c donor mice into C57BL/6 recipient mice. Polymer treated and untreated grafts were assessed by serology and histology at various timepoints (day 2, 15 and 42 for vessel grafts and day 30 for renal grafts). Results: In vitro, polymer modified endothelial cells were able to evade CAR-T cell induced cytoxicity and reduced oxidative stress. Moreover, polymer treatment reduced TNF release in M1 macrophages. In vivo, modified grafts showed reduced medial thickening and leukocyte infiltration in vessel transplants; further confirmed in the reduction of pro-inflammatory cytokines in serum. In 42 day studies, donor-specific antibody was reduced in polymer-treated grafts compared to untreated. Finally, histological analysis of polymer-treated renal grafts revealed less infiltration and mesangial expansion relating to a healthier graft after 30 days.Conclusion: Here, the use of a polymer-mediated organ engineering approach leads to vascular protection that prevents immune-mediated rejection of organ transplants. Ex-vivo delivery of these immune cloaking polymers that engineer the blood vessel lumen allow for localized immune protection, making this an enticing and viable strategy for the reduction in the use of broad-active immunosuppressants post-transplantation. The protocol remains simple and easy to deliver, thereby enhancing its potential clinical applicability. To further validate this novel approach, studies in larger animal models that more closely replicate human transplant conditions are being planned. Canadian Institutes of Health Research. Natural Sciences and Engineering Council of Canada. Heart and Stroke Foundation of Canada. Canadian Glycomics Network, GlycoNet.

A comprehensive review on applications of 3D printing in natural fibers polymer composites for biomedical applications

Over the past few decades, three-dimensional (3D) printing technologies have surpassed the conventional manufacturing techniques due to their wide applications and advantages. The applications of 3D printing in biomedical field is ever increasing due to improvement in accuracy and surface quality of products. The development of biomedical implants through patient specific data and rapid tooling techniques has revolutionized the research activities. Now-a-days, the metal printers have capability to directly create metal implants using biocompatible metallic alloys. This paper focuses on the potential applications of 3D printing in biomedical fields with specific emphasis on tissue engineering and bio-printing of organs using bio-inks. This paper also reviews various biocompatible and biodegradable materials used in recent in-vivo and in-vitro studies. It has been deduced from the study that use of natural fibers in polymers resulted in improved mechanical strength of products. Also, the implementation of additive manufacturing technologies for production of composites would lead to production of customized product.

High level of polarized engraftment of porcine intrahepatic cholangiocyte organoids in decellularized liver scaffolds.

In Europe alone, each year 5500 people require a life‐saving liver transplantation, but 18% die before receiving one due to the shortage of donor organs. Whole organ engineering, utilizing decellularized liver scaffolds repopulated with autologous cells, is an attractive alternative to increase the pool of available organs for transplantation. The development of this technology is hampered by a lack of a suitable large‐animal model representative of the human physiology and a reliable and continuous cell source. We have generated porcine intrahepatic cholangiocyte organoids from adult stem cells and demonstrate that these cultures remained stable over multiple passages whilst retaining the ability to differentiate into hepatocyte‐ and cholangiocyte‐like cells. Recellularization onto porcine scaffolds was efficient and the organoids homogeneously differentiated, even showing polarization. Our porcine intrahepatic cholangiocyte system, combined with porcine liver scaffold paves the way for developing whole liver engineering in a relevant large‐animal model.

Problems of creating bioartificial organs and the competition of medical technologies

A crucial direction in the development of biotechnology is production of human bioartificial organs and of related products for tissue and organ engineering – constituent components for biofabrications of organs and tissues: human biopolymers of extracellular matrix (ECM), cytokines, biomass of autologous and allogeneic human cells, organoids and tissue spheroids, as well as special equipment – tissue bioreactors, bioprinters, etc. The biotechnology development level today allows creating live ‗spare parts‘ for humans, and there is the prospect of competition with manufacturers of prostheses and implants. The present review considers the unsolved problems of creating bioartificial organs from the perspective of the classical triad of tissue engineering technology – cells, scaffold, and bioreactor. The author focuses on clinical examples and discusses possible strategies and new approaches for growing bioartificial organs inside in vivo bioreactors (hereinafter –regeneratrons) integrated with a living organism. Regeneratrons are the latest generation of tissue bioreactorsrarely used in clinical practice yet with a potential of increasing the efficiency of treatment.

Bimorph electrothermal micro-gripper with large deformation, precise and rapid response, and low operating voltage

Micro-grippers are highly desired in engineering, robotics, and biomedicine. However, on the basis of satisfying the requirements of miniaturization, precise manipulation, and low power consumption, the existing micro-grippers are difficult to achieve rapid response simultaneously. In this paper, we present a bimorph electrothermal micro-gripper that composed of several metal ultrathin films with high surface-to-volume ratios, allowing rapid heating and cooling processes. Patterns of these films are exquisitely designed so that the micro-gripper naturally forms an embedded circuit to optimize the current distribution. The micro-gripper can be precisely actuated under voltages below 2 V, while dramatically responding to pulse voltages up to 100 Hz. By interacting with a silica particle 96 times heavier than its weight, potential applications of the micro-gripper in robotics, organic tissue engineering, and interventional surgery can be shown. The advantage to be compatible with other semiconductor components ensures that the functions of the micro-gripper can be further expanded.

Solvation of small gold clusters in supercritical water

Solvation in supercritical water features fascinating properties such as the selective dissolution or precipitation of non-polar versus polar species. This is known since long to open up astonishing possibilities in organic synthesis, catalysis, or engineering. Less known is the role that supercritical aqueous solutions play close to hydrothermal vents in the deep sea and in ore deposit formation in Earth’s crust. Within this realm, we explore here the solvation of small uncharged gold species, namely the gold dimer and tetramer, in supercritical water in terms of structural and electronic properties using ab initio molecular dynamics simulations. Our simulations reveal that a highly anisotropic first solvation shell is formed around these gold clusters which consists of less than two water molecules on average. Importantly, we find very significant charge transfer and polarization effects between these water molecules and the neutral gold particles, which cannot be captured when using non-polarizable force fields. These electronic many-body effects lead not only to enormous dipole moment fluctuations of the gold clusters themselves, but also to an unexpectedly strong increase of the average effective dipole moments in their first solvation shell. Thus, supercritical solutions of gold particles in water turn out to be surprisingly complex.

Advances in 4D printing: from stimulation to simulation.

The advancement of four-dimensional (4D) printing has been fueled by the rise in demand for additive manufacturing and the expansion in shape-memory materials. The printing of smart substances that respond to external stimuli is known as 4D printing. 4D printing allows highly controlled shapes to simulate the physiological milieu by adding time dimensions. The 4D printing is suitable with current progress in smart compounds, printers, and its mechanism of action. The 4D printing paradigm, a revolutionary enhancement of 3D printing, was anticipated by various engineering disciplines. Tissue engineering, medicinal, consumer items, aerospace, and organ engineering use 4D printing technology. The current review mainly focuses on the basics of 4D printing and the methods used therein. It also discusses the time-dependent behavior of stimulus-sensitive compounds, which are widely used in 4D printing. In addition, this review highlights material aspects, specifically related to shape-memory polymers, stimuli-responsive materials (classified as physical, chemical, and biological), and modified materials, the backbone of 4D printing technology. Finally, potential applications of 4D printing in the biomedical sector are also discussed with challenges and future perspectives.

Biomedical Applications of MXene‐Integrated Composites: Regenerative Medicine, Infection Therapy, Cancer Treatment, and Biosensing

AbstractMXenes (viz., transition metal carbides, carbonitrides, and nitrides) have emerged as a new subclass of 2D materials. Due to their outstanding physicochemical and biological properties, MXenes have gained much attention in the biomedical field in recent years, including drug delivery systems, regenerative medicine, and biosensing. Additionally, the incorporation of MXenes into hydrogels has garnered significant interest in biomedical engineering as an electroactive and mechanical nanoreinforcer capable of converting nonconductive scaffolds into excellent conductors of electricity with an impressive effect on mechanical properties for the engineering of electroactive organs and tissues such as cardiac, skeletal muscle, and nerve. However, many questions and problems remain unresolved that need to be answered to usher these 2D materials toward their true destiny. Thus, this review paper aims to provide an overview of the design and applications of MXene‐integrated composites for biomedical applications, including cardiac tissue engineering, wound healing, infection therapy, cancer therapy, and biosensors. Moreover, the current challenges and limitations of utilizing MXenes in vivo are highlighted and discussed, followed by its prospects as a guideline toward possible various futuristic biomedical applications. This review article will inspire researchers, who search for properties, opportunities, and challenges of using this 2D nanomaterial in biomedical applications.

Light Management through Organic Bulk Heterojunction and Carrier Interfacial Engineering for Perovskite Solar Cells with 23.5% Efficiency

AbstractLight management through organic bulk heterojunction (BHJ) has been widely reported to push up the performance of lead‐based perovskite solar cells (PSCs) by extending the spectral response. However, the development of integrated perovskite/organic bulk heterojunction solar cells (IPSCs) encounters a bottleneck problem that the poor carrier extraction capability of perovskite and BHJ leads to the severe loss of open‐voltage (Voc) and fill factor (FF). Herein, the strategy of introducing black phosphorous quantum dots (BPQDs) and cuprous oxide (CuOx) into IPSCs is adopted, which not only successfully extends the single‐component PSCs light response to 930 nm, but also significantly reduces the Voc and FF loss of IPSCs. BPQDs with bipolar charge transport and high mobility characteristics improves the electron/hole transport behaviors of perovskite and BHJ films. CuOx with matching energy levels is introduced between BHJ and Spiro‐OMeTAD as a buffer layer, which provides good driving force for the transportation of holes. The champion device achieves a power conversion efficiency of 23.52%. The IPSCs devices also display an excellent long‐term and humidity stability. This work demonstrates an approach to solve the carrier extraction key issues that limits the performance of IPSCs, which achieves an instructive result in the development of PSCs light management.

Air-loaded Gas Vesicle Nanoparticles Promote Cell Growth in Three-dimensional Bioprinted Tissue Constructs.

Three-dimensional (3D) bioprinting has emerged as a promising method for the engineering of tissues and organs. Still, it faces challenges in its widespread use due to issues with the development of bioink materials and the nutrient diffusion barrier inherent to these scaffold materials. Herein, we introduce a method to promote oxygen diffusion throughout the printed constructs using genetically encoded gas vesicles derived from haloarchaea. These hollow nanostructures are composed of a protein shell that allows gases to permeate freely while excluding the water flow. After printing cells with gas vesicles of various concentrations, the cells were observed to have increased activity and proliferation. These results suggest that air-filled gas vesicles can help overcome the diffusion barrier throughout the 3D bioprinted constructs by increasing oxygen availability to cells within the center of the construct. The biodegradable nature of the gas vesicle proteins combined with our promising results encourage their potential use as oxygen-promoting materials in biological samples.

Ionic Detergent Under Pressure-Vacuum as an Innovative Strategy to Generate Canine Tracheal Scaffold for Organ Engineering

Decellularized scaffolds applied in tissue engineering offer improvements, supplying the elevated necessity for organs and tissues for replacement. However, obtaining a functional trachea for autotransplantation or allotransplantation is tricky due to the organ anatomical and structural complexity. Most tracheal decellularization protocols are lengthy, expensive, and could damage the tracheal extracellular matrix (ECM) architecture and functionality. Here, we aimed to evaluate the effectiveness of 3 different decellularization protocols combined with chemical and physical methods to obtain acellular canine tracheal scaffolds. Six adult dog tracheas were incised (tracheal segments) resulting in 28 rings for control tissue and 84 rings for decellularization (5–7 mm thick). Subsequently, decellularized tracheal scaffolds were microscopically/macroscopically characterized by histological analysis (Hematoxylin-Eosin, Masson’s trichrome, Picrosirius red, Alcian blue, and Safranin O), immunohistochemistry for ECM components, scanning electron microscopy, and genomic DNA quantification. After decellularization, the tracheal tissue revealed reduced genomic DNA, and maintenance of ECM components preserved (structural proteins, adhesive glycoproteins, glycosaminoglycans and proteoglycans), suggesting ECM integrity and functionality. Comparatively, the combined ionic detergent with high vacuum pressure decellularization protocol revealed superior genomic DNA decrease (13.5 ng/mg) and improvement on glycosaminoglycans and proteoglycans preservation regarding the other decellularized trachea scaffolds and native tissue. Our results indicate that the 3 chemical/physical protocols reduce the decellularization time without ECM proteins damage. Notwithstanding, the use of ionic detergent under vacuum pressure was able to generate an innovative strategy to obtain acellular canine tracheal scaffolds with the highest levels of adhesive proteins that support its potentiality for recellularization and future tissue engineering application.

Application Status of Sacrificial Biomaterials in 3D Bioprinting.

Additive manufacturing, also known as three-dimensional (3D) printing, relates to several rapid prototyping (RP) technologies, and has shown great potential in the manufacture of organoids and even complex bioartificial organs. A major challenge for 3D bioprinting complex org unit ans is the competitive requirements with respect to structural biomimeticability, material integrability, and functional manufacturability. Over the past several years, 3D bioprinting based on sacrificial templates has shown its unique advantages in building hierarchical vascular networks in complex organs. Sacrificial biomaterials as supporting structures have been used widely in the construction of tubular tissues. The advent of suspension printing has enabled the precise printing of some soft biomaterials (e.g., collagen and fibrinogen), which were previously considered unprintable singly with cells. In addition, the introduction of sacrificial biomaterials can improve the porosity of biomaterials, making the printed structures more favorable for cell proliferation, migration and connection. In this review, we mainly consider the latest developments and applications of 3D bioprinting based on the strategy of sacrificial biomaterials, discuss the basic principles of sacrificial templates, and look forward to the broad prospects of this approach for complex organ engineering or manufacturing.

Customized Synthesis: Solvent- and Acid-Assisted Topology Evolution in Zirconium-Tetracarboxylate Frameworks.

Metal-organic frameworks (MOFs) demonstrate strong potential for various important applications due to their well tunable structures and compositions through metal and organic linker engineering. As an effective approach, topology evolution by controlling linker conformation has received considerable attention, where solvents and acids have crucial effects on structural formation. However, a systematic study of such effects remains under investigated. Herein, we carried out a methodical study on the topology evolution in Zr-MOFs directed by solvothermal conditions with various combinations of three common solvents and six different acids. As a result, three Zr-MOFs with different topologies, scu (HIAM-4007), scp (HIAM-4008), and csq (HIAM-4009), were obtained using the same Zr6-cluster and tetratopic carboxylate linker, in which structure diversity shows significant influence on their corresponding photoluminescence quantum yields. Further experiments revealed that the acidity of acids and the basicity of solvents strongly influenced the linker conformation in the resultant MOFs, leading to the topology evolution. Such a solvent- and acid-assisted topology evolution represents a general approach that can be used with other tetratopic carboxylate linkers to realize structural diversity. The present work demonstrates an effective structure designing strategy by controlling synthetic conditions, which may prove to be powerful for customized synthesis of MOFs with specific structure and functionality.

Ultrastable and High‐Rate 2D Siloxene Anode Enabled by Covalent Organic Framework Engineering for Advanced Lithium‐Ion Batteries

Siloxene as a new type of 2D material has wide potential applications due to its special structure. Especially, as anode for lithium-ion batteries, siloxene shows promising prospect due to its small volume change and low diffusion pathway. However, the unstable solid electrolyte interphase and low electronic conductivity lead to the low Coulombic efficiency, poor rate capability, and limited cycling performance. To settle the problems, a thin porous covalent organic framework (COF) coating layer is designed by in situ growth on micro-sized siloxene. With the inherent ionic conductive and electrolyte compatible advantages of COF, the engineered siloxene demonstrates superior electrochemical performance with 96% capacity retention at 8 A g-1 for 1500 cycles.

Protease inhibitor Camostat Mesyalte blocks wild type SARS-CoV-2 and D614G viral entry in human engineered miniature lungs

The catastrophic global effects of the SARS-CoV-2 pandemic highlight the need to develop novel therapeutics strategies to prevent and treat viral infections of the respiratory tract. To enable this work, we need scalable, affordable, and physiologically relevant models of the human lung, the primary organ involved in the pathogenesis of COVID-19. To date, most COVID-19 in vitro models rely on platforms such as cell lines and organoids. While 2D and 3D models have provided important insights, human distal lung models that can model epithelial viral uptake have yet to be established. We hypothesized that by leveraging techniques of whole organ engineering and directed differentiation of induced pluripotent stem cells (iPSC) we could model human distal lung epithelium, examine viral infection at the tissue level in real time, and establish a platform for COVID-19 related research ex vivo. In the present study, we used type 2 alveolar epithelial cells (AT2) derived from human iPSCs to repopulate whole rat lung acellular scaffolds and maintained them in extended biomimetic organ culture for 30 days to induce the maturation of distal lung epithelium. We observed emergence of a mixed type 1 and type 2 alveolar epithelial phenotype during tissue formation. When exposing our system to a pseudotyped lentivirus containing the spike of wildtype SARS-CoV-2 and the more virulent D614G, we observed progression of the infection in real time. We then found that the protease inhibitor Camostat Mesyalte significantly reduced viral transfection in distal lung epithelium. In summary, our data show that a mature human distal lung epithelium can serve as a novel moderate throughput research platform to examine viral infection and to evaluate novel therapeutics ex vivo.

Suppressing the Formation of High n-Phase and 3D Perovskites in the Fabrication of Ruddlesden–Popper Perovskite Thin Films by Bulky Organic Cation Engineering

Suppressing the Formation of High <i>n</i>-Phase and 3D Perovskites in the Fabrication of Ruddlesden–Popper Perovskite Thin Films by Bulky Organic Cation Engineering