3D tissue engineering, an emerging technique for pharmaceutical research

Phenotypic Screening of Prospective Analgesics Among FDA-Approved Compounds using an iPSC-Based Model of Acute and Chronic Inflammatory Nociception

Classical target-based drug screening is low-throughput, largely subjective, and costly. Phenotypic screening based on in vitro models is increasingly being used to identify candidate compounds that modulate complex cell/tissue functions. Chronic inflammatory nociception, and subsequent chronic pain conditions, affect peripheral sensory neuron activity (e.g., firing of action potentials) through myriad pathways, and remain unaddressed in regard to effective, non-addictive management/treatment options. Here, a chronic inflammatory nociception model is demonstrated based on induced pluripotent stem cell (iPSC) sensory neurons and glia, co-cultured on microelectrode arrays (MEAs). iPSC sensory co-cultures exhibit coordinated spontaneous extracellular action potential (EAP) firing, reaching a stable baseline after ≈27 days in vitro (DIV). Spontaneous and evoked EAP metrics are significantly modulated by 24-h incubation with tumor necrosis factor-alpha (TNF-α), representing an inflammatory phenotype. Compared with positive controls (lidocaine), this model is identified as an "excellent" stand-alone assay based on a modified Z' assay quality metric. This model is then used to screen 15 cherry-picked, off-label, Food and Drug Administration (FDA)-approved compounds; 10 of 15 are identified as "hits". Both hits and "misses" are discussed in turn. In total, this data suggests that iPSC sensory co-cultures on MEAs may represent a moderate-to-high-throughput assay for drug discovery targeting inflammatory nociception.

Recent progresses in neural tissue engineering using topographic scaffolds

Neural tissue engineering as alternatives to recover damaged tissues and organs is getting more and more attention due to the lack of regeneration ability of natural tissue nervous system after injury. Particularly, topographic scaffolds are one of the critical elements to guide nerve orientation and reconnection with characteristics of mimic the natural extracellular matrix. This review focuses on scaffolds preparation technologies, topographical features, scaffolds-based encapsulations delivery strategies for neural tissue regeneration, biological functions on nerve cell guidance and regeneration, and applications of topographic scaffolds in vivo and in vitro. Here, the recent developments in topographic scaffolds for neural tissue engineering by simulating neural cell topographic orientation and differentiation are presented. We also explore the challenges and future perspectives of topographical scaffolds in clinical trials and practical applications.

3D Prestress Bioprinting of Directed Tissues

Many mammalian tissues adopt a specific cellular arrangement under stress stimulus that enables their unique function. However, conventional 3D encapsulation often fails to recapitulate the complexities of these arrangements, thus motivating the need for advanced cellular arrangement approaches. Here, an original 3D prestress bioprinting approach of directed tissues under the synergistic effect of static sustained tensile stress and molecular chain orientation, with an aid of slow crosslinking in bioink, is developed. The semi-crosslinking state of the designed bioink exhibits excellent elasticity for applying stress on the cells during the sewing-like process. After bioprinting, the bioink gradually forms complete crosslinking and keeps the applied stress force to induce cell-orientated growth. More importantly, multiple cell types can be arranged directionally by this approach, while the internal stress of the hydrogel filament is also adjustable. In addition, compared with conventional bioprinted skin, the 3D prestress bioprinted skin results in a better wound healing effect due to promoting the angiogenesis of granulation tissue. This study provides a prospective strategy to engineer skeletal muscles, as well as tendons, ligaments, vascular networks, or combinations thereof in the future.

High-throughput design of cultured tissue moulds using a biophysical model: optimising cell alignment

The technique presented here identifies tethered mould designs, optimised for growing cultured tissue with very highly-aligned cells. It is based on a microscopic biophysical model for polarised cellular hydrogels. There is an unmet need for tools to assist mould and scaffold designs for the growth of cultured tissues with bespoke cell organisations, that can be used in applications such as regenerative medicine, drug screening and cultured meat. High-throughput biophysical calculations were made for a wide variety of computer-generated moulds, with cell-matrix interactions and tissue-scale forces simulated using a contractile network dipole orientation model. Elongated moulds with central broadening and one of the following tethering strategies are found to lead to highly-aligned cells: (1) tethers placed within the bilateral protrusions resulting from an indentation on the short edge, to guide alignment (2) tethers placed within a single vertex to shrink the available space for misalignment. As such, proof-of-concept has been shown for mould and tethered scaffold design based on a recently developed biophysical model. The approach is applicable to a broad range of cell types that align in tissues and is extensible for 3D scaffolds.

Rapid prediction of lab-grown tissue properties using deep learning

The interactions between cells and the extracellular matrix are vital for the self-organisation of tissues. In this paper we present proof-of-concept to use machine learning tools to predict the role of this mechanobiology in the self-organisation of cell-laden hydrogels grown in tethered moulds. We develop a process for the automated generation of mould designs with and without key symmetries. We create a large training set withN = 6400 cases by running detailed biophysical simulations of cell-matrix interactions using the contractile network dipole orientation model for the self-organisation of cellular hydrogels within these moulds. These are used to train an implementation of thepix2pixdeep learning model, with an additional 100 cases that were unseen in the training of the neural network for review and testing of the trained model. Comparison between the predictions of the machine learning technique and the reserved predictions from the biophysical algorithm show that the machine learning algorithm makes excellent predictions. The machine learning algorithm is significantly faster than the biophysical method, opening the possibility of very high throughput rational design of moulds for pharmaceutical testing, regenerative medicine and fundamental studies of biology. Future extensions for scaffolds and 3D bioprinting will open additional applications.

Systematic Comparison of Commercial Hydrogels Revealed That a Synergy of Laminin and Strain-Stiffening Promotes Directed Migration of Neural Cells

Hydrogels have shown potential in replacing damaged nerve tissue, but the ideal hydrogel is yet to be found. In this study, various commercially available hydrogels were compared. Schwann cells, fibroblasts, and dorsal root ganglia neurons were seeded on the hydrogels, and their morphology, viability, proliferation, and migration were examined. Additionally, detailed analyses of the gels' rheological properties and topography were conducted. Our results demonstrate vast differences on cell elongation and directed migration on the hydrogels. Laminin was identified as the driver behind cell elongation and in combination with a porous, fibrous, and strain-stiffening matrix structure responsible for oriented cell motility. This study improves our understanding of cell-matrix interactions and thereby facilitates tailored fabrication of hydrogels in the future.

3D engineered tissue models for studying human-specific infectious viral diseases

Viral infections cause damage to various organ systems by inducing organ-specific symptoms or systemic multi-organ damage. Depending on the infection route and virus type, infectious diseases are classified as respiratory, nervous, immune, digestive, or skin infections. Since these infectious diseases can widely spread in the community and their catastrophic effects are severe, identification of their causative agent and mechanisms underlying their pathogenesis is an urgent necessity. Although infection-associated mechanisms have been studied in two-dimensional (2D) cell culture models and animal models, they have shown limitations in organ-specific or human-associated pathogenesis, and the development of a human-organ-mimetic system is required. Recently, three-dimensional (3D) engineered tissue models, which can present human organ-like physiology in terms of the 3D structure, utilization of human-originated cells, recapitulation of physiological stimuli, and tight cell–cell interactions, were developed. Furthermore, recent studies have shown that these models can recapitulate infection-associated pathologies. In this review, we summarized the recent advances in 3D engineered tissue models that mimic organ-specific viral infections. First, we briefly described the limitations of the current 2D and animal models in recapitulating human-specific viral infection pathology. Next, we provided an overview of recently reported viral infection models, focusing particularly on organ-specific infection pathologies. Finally, a future perspective that must be pursued to reconstitute more human-specific infectious diseases is presented.

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3D in vitro models are different from the traditional model in the infection process.

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Human-specific infection research requires a 3D microenvironment and human cells.

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3D in vitro infectious models can be useful for basic research on infectious disease.

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3D in vitro infectious models recapitulate the complex cell-virus-immune interaction.

Recent progress in the manipulation of biochemical and biophysical cues for engineering functional tissues

Tissue engineering (TE) is currently considered a cutting-edge discipline that offers the potential for developing treatments for health conditions that negatively affect the quality of life. This interdisciplinary field typically involves the combination of cells, scaffolds, and appropriate induction factors for the regeneration and repair of damaged tissue. Cell fate decisions, such as survival, proliferation, or differentiation, critically depend on various biochemical and biophysical factors provided by the extracellular environment during developmental, physiological, and pathological processes. Therefore, understanding the mechanisms of action of these factors is critical to accurately mimic the complex architecture of the extracellular environment of living tissues and improve the efficiency of TE approaches. In this review, we recapitulate the effects that biochemical and biophysical induction factors have on various aspects of cell fate. While the role of biochemical factors, such as growth factors, small molecules, extracellular matrix (ECM) components, and cytokines, has been extensively studied in the context of TE applications, it is only recently that we have begun to understand the effects of biophysical signals such as surface topography, mechanical, and electrical signals. These biophysical cues could provide a more robust set of stimuli to manipulate cell signaling pathways during the formation of the engineered tissue. Furthermore, the simultaneous application of different types of signals appears to elicit synergistic responses that are likely to improve functional outcomes, which could help translate results into successful clinical therapies in the future.

The Natural Products Withaferin A and Withanone from the Medicinal Herb Withania somnifera Are Covalent Inhibitors of the SARS-CoV-2 Main Protease

The current COVID-19 pandemic caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) created a global health crisis. The ability of vaccines to protect immunocompromised individuals and from emerging new strains are major concerns. Hence antiviral drugs against SARS-CoV-2 are essential. The SARS-CoV-2 main protease Mpro is vital for replication and an important target for antivirals. Using CMap analysis and docking studies, withaferin A (wifA) and withanone (win), two natural products from the medicinal herb Withania somnifera (ashwagandha), were identified as promising candidates that can covalently inhibit the viral protease Mpro. Cell culture, enzymatic, LC-MS/MS, computational, and equilibrium dialysis based assays were performed. DFT calculations indicated that wifA and win can form stable adducts with thiols. The cytotoxicity of Mpro was significantly reduced by wifA and win. Both wifA and win were found to irreversibly inhibit 0.5 μM Mpro with IC50 values of 0.54 and 1.8 μM, respectively. LC-MS/MS analysis revealed covalent adduct formation with wifA at cysteines 145 and 300 of Mpro. The natural products wifA and win can irreversibly inhibit the SARS-CoV-2 main protease Mpro. Based on the work presented here we propose that both wifA and win have the potential to be safely used as preventative and therapeutic interventions for COVID-19.

Tissue-Engineered Models of the Human Brain: State-of-the-Art Analysis and Challenges

Neurological disorders affect billions of people across the world, making the discovery of effective treatments an important challenge. The evaluation of drug efficacy is further complicated because of the lack of in vitro models able to reproduce the complexity of the human brain structure and functions. Some limitations of 2D preclinical models of the human brain have been overcome by the use of 3D cultures such as cell spheroids, organoids and organs-on-chip. However, one of the most promising approaches for mimicking not only cell structure, but also brain architecture, is currently represented by tissue-engineered brain models. Both conventional (particularly electrospinning and salt leaching) and unconventional (particularly bioprinting) techniques have been exploited, making use of natural polymers or combinations between natural and synthetic polymers. Moreover, the use of induced pluripotent stem cells (iPSCs) has allowed the co-culture of different human brain cells (neurons, astrocytes, oligodendrocytes, microglia), helping towards approaching the central nervous system complexity. In this review article, we explain the importance of in vitro brain modeling, and present the main in vitro brain models developed to date, with a special focus on the most recent advancements in tissue-engineered brain models making use of iPSCs. Finally, we critically discuss achievements, main challenges and future perspectives.

Travelling-Wave and Asymptotic Analysis of a Multiphase Moving Boundary Model for Engineered Tissue Growth

We derive a multiphase, moving boundary model to represent the development of tissue in vitro in a porous tissue engineering scaffold. We consider a cell, extra-cellular liquid and a rigid scaffold phase, and adopt Darcy’s law to relate the velocity of the cell and liquid phases to their respective pressures. Cell–cell and cell–scaffold interactions which can drive cellular motion are accounted for by utilising relevant constitutive assumptions for the pressure in the cell phase. We reduce the model to a nonlinear reaction–diffusion equation for the cell phase, coupled to a moving boundary condition for the tissue edge, the diffusivity being dependent on the cell and scaffold volume fractions, cell and liquid viscosities and parameters that relate to cellular motion. Numerical simulations reveal that the reduced model admits three regimes for the evolution of the tissue edge at large time: linear, logarithmic and stationary. Employing travelling-wave and asymptotic analysis, we characterise these regimes in terms of parameters related to cellular production and motion. The results of our investigation allow us to suggest optimal values for the governing parameters, so as to stimulate tissue growth in an engineering scaffold.

Human Heart Anoxia and Reperfusion Tissue (HEART) Model for the Rapid Study of Exosome Bound miRNA Expression As Biomarkers for Myocardial Infarction

Current biomarkers for myocardial infarction (MI) diagnosis are typically late markers released upon cell death, incapable of distinguishing between ischemic and reperfusion injury and can be symptoms of other pathologies. Circulating microRNAs (miRNAs) have recently been proposed as alternative biomarkers for MI diagnosis; however, detecting the changes in the human cardiac miRNA profile during MI is extremely difficult. Here, to study the changes in miRNA levels during acute MI, a heart-on-chip model with a cardiac channel, containing human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes in human heart decellularized matrix and collagen, and a vascular channel, containing hiPSC-derived endothelial cells, is developed. This model is exposed to anoxia followed by normoxia to mimic ischemia and reperfusion, respectively. Using a highly sensitive miRNA biosensor that the authors developed, the exact same increase in miR-1, miR-208b, and miR-499 levels in the MI-on-chip and the time-matched human blood plasma samples collected before and after ischemia and reperfusion, is shown. That the surface marker profile of exosomes in the engineered model changes in response to ischemic and reperfusion injury, which can be used as biomarkers to detect MI, is also shown. Hence, the MI-on-chip model developed here can be used in biomarker discovery.

Highlights on Advancing Frontiers in Tissue Engineering

The field of tissue engineering continues to advance, sometimes in exponential leaps forward, but also sometimes at a rate that does not fulfill the promise that the field imagined a few decades ago. This review is in part a catalog of success in an effort to inform the process of innovation. Tissue engineering has recruited new technologies and developed new methods for engineering tissue constructs that can be used to mitigate or model disease states for study. Key to this antecedent statement is that the scientific effort must be anchored in the needs of a disease state and be working toward a functional product in regenerative medicine. It is this focus on the wildly important ideas coupled with partnered research efforts within both academia and industry that have shown most translational potential. The field continues to thrive and among the most important recent developments are the use of three-dimensional bioprinting, organ-on-a-chip, and induced pluripotent stem cell technologies that warrant special attention. Developments in the aforementioned areas as well as future directions are highlighted in this article. Although several early efforts have not come to fruition, there are good examples of commercial profitability that merit continued investment in tissue engineering. Impact statement Tissue engineering led to the development of new methods for regenerative medicine and disease models. Among the most important recent developments in tissue engineering are the use of three-dimensional bioprinting, organ-on-a-chip, and induced pluripotent stem cell technologies. These technologies and an understanding of them will have impact on the success of tissue engineering and its translation to regenerative medicine. Continued investment in tissue engineering will yield products and therapeutics, with both commercial importance and simultaneous disease mitigation.

Decellularized extracellular matrix scaffolds: Recent trends and emerging strategies in tissue engineering

The application of scaffolding materials is believed to hold enormous potential for tissue regeneration. Despite the widespread application and rapid advance of several tissue-engineered scaffolds such as natural and synthetic polymer-based scaffolds, they have limited repair capacity due to the difficulties in overcoming the immunogenicity, simulating in-vivo microenvironment, and performing mechanical or biochemical properties similar to native organs/tissues. Fortunately, the emergence of decellularized extracellular matrix (dECM) scaffolds provides an attractive way to overcome these hurdles, which mimic an optimal non-immune environment with native three-dimensional structures and various bioactive components. The consequent cell-seeded construct based on dECM scaffolds, especially stem cell-recellularized construct, is considered an ideal choice for regenerating functional organs/tissues. Herein, we review recent developments in dECM scaffolds and put forward perspectives accordingly, with particular focus on the concept and fabrication of decellularized scaffolds, as well as the application of decellularized scaffolds and their combinations with stem cells (recellularized scaffolds) in tissue engineering, including skin, bone, nerve, heart, along with lung, liver and kidney.

Versatile activity and morphological effects of zinc oxide submicron particles as anticancer agents

Background: Submicron particles (SMPs), as novel bionanomaterials, offer complementary benefits to their conventional nano-counterparts. Aim: To explore zinc oxide (ZnO) SMPs' bioimaging and anticancer potentials. Materials & methods: ZnO SMPs were synthesized into two shapes. Fluorescent spectrum and microscopy were studied for the bioimaging property. Wound healing and Live/Dead assays of glioblastoma cells were characterized for anticancer activities. Results: ZnO SMPs exhibited a high quantum yield (49%) with stable orange fluorescence emission. Both morphologies (most significant in the rod shape) showed tumor-selective properties in cytotoxicity, inhibition to cell migration and attenuating the cancer-upregulated genes. The tumor selectivity was attributed to particle degradation and surface properties on pH dependency. Conclusion: The authors propose that ZnO SMPs could be a promising anticancer drug with tunable, morphology-dependent properties for bioimaging and controlled release.

Cellular Interaction of Bone Marrow Mesenchymal Stem Cells with Polymer and Hydrogel 3D Microscaffold Templates

Biomimicking biological niches of healthy tissues or tumors can be achieved by means of artificial microenvironments, where structural and mechanical properties are crucial parameters to promote tissue formation and recreate natural conditions. In this work, three-dimensional (3D) scaffolds based on woodpile structures were fabricated by two-photon polymerization (2PP) of different photosensitive polymers (IP-S and SZ2080) and hydrogels (PEGDA 700) using two different 2PP setups, a commercial one and a customized one. The structures' properties were tuned to study the effect of scaffold dimensions (gap size) and their mechanical properties on the adhesion and proliferation of bone marrow mesenchymal stem cells (BM-MSCs), which can serve as a model for leukemic diseases, among other hematological applications. The woodpile structures feature gap sizes of 25, 50, and 100 μm and a fixed beam diameter of 25 μm, to systematically study the optimal cell colonization that promotes healthy cell growth and potential tissue formation. The characterization of the scaffolds involved scanning electron microscopy and mechanical nanoindenting, while their suitability for supporting cell growth was evaluated with live/dead cell assays and multistaining 3D confocal imaging. In the mechanical assays of the hydrogel material, we observed two different stiffness ranges depending on the indentation depth. Larger gap woodpile structures coated with fibronectin were identified as the most promising scaffolds for 3D BM-MSC cellular models, showing higher proliferation rates. The results indicate that both the design and the employed materials are suitable for further assays, where retaining the BM-MSC stemness and original features is crucial, including studies focused on BM disorders such as leukemia and others. Moreover, the combination of 3D scaffold geometry and materials holds great potential for the investigation of cellular behaviors in a co-culture setting, for example, mesenchymal and hematopoietic stem cells, to be further applied in medical research and pharmacological studies.

3D Tissue-Engineered Vascular Drug Screening Platforms: Promise and Considerations

Despite the efforts devoted to drug discovery and development, the number of new drug approvals have been decreasing. Specifically, cardiovascular developments have been showing amongst the lowest levels of approvals. In addition, concerns over the adverse effects of drugs to the cardiovascular system have been increasing and resulting in failure at the preclinical level as well as withdrawal of drugs post-marketing. Besides factors such as the increased cost of clinical trials and increases in the requirements and the complexity of the regulatory processes, there is also a gap between the currently existing pre-clinical screening methods and the clinical studies in humans. This gap is mainly caused by the lack of complexity in the currently used 2D cell culture-based screening systems, which do not accurately reflect human physiological conditions. Cell-based drug screening is widely accepted and extensively used and can provide an initial indication of the drugs' therapeutic efficacy and potential cytotoxicity. However, in vitro cell-based evaluation could in many instances provide contradictory findings to the in vivo testing in animal models and clinical trials. This drawback is related to the failure of these 2D cell culture systems to recapitulate the human physiological microenvironment in which the cells reside. In the body, cells reside within a complex physiological setting, where they interact with and respond to neighboring cells, extracellular matrix, mechanical stress, blood shear stress, and many other factors. These factors in sum affect the cellular response and the specific pathways that regulate variable vital functions such as proliferation, apoptosis, and differentiation. Although pre-clinical in vivo animal models provide this level of complexity, cross species differences can also cause contradictory results from that seen when the drug enters clinical trials. Thus, there is a need to better mimic human physiological conditions in pre-clinical studies to improve the efficiency of drug screening. A novel approach is to develop 3D tissue engineered miniaturized constructs in vitro that are based on human cells. In this review, we discuss the factors that should be considered to produce a successful vascular construct that is derived from human cells and is both reliable and reproducible.

Nanoarchitectonics of a Microsphere-Based Scaffold for Modeling Neurodevelopment and Neurological Disease

Three-dimensional cellular constructs derived from pluripotent stem cells allow the ex vivo study of neurodevelopment and neurological disease within a spatially organized model. However, the robustness and utility of three-dimensional models is impacted by tissue self-organization, size limitations, nutrient supply, and heterogeneity. In this work, we have utilized the principles of nanoarchitectonics to create a multifunctional polymer/bioceramic composite microsphere system for stem cell culture and differentiation in a chemically defined microenvironment. Microspheres could be customized to produce three-dimensional structures of defined size (ranging from >100 to <350 μm) with lower mechanical properties compared with a thin film. Furthermore, the microspheres softened in solution, approaching more tissue-like mechanical properties over time. With neural stem cells (NSCs) derived from human induced pluripotent stem cells, microsphere-cultured NSCs were able to utilize multiple substrates to promote cell adhesion and proliferation. Prolonged culture of NSC-bound microspheres under differentiating conditions allowed the formation of both neural and glial cell types from control and patient-derived stem cell models. Human NSCs and differentiated neurons could also be cocultured with astrocytes and human umbilical vein endothelial cells, demonstrating application for tissue-engineered modeling of development and human disease. We further demonstrated that microspheres allow the loading and sustained release of multiple recombinant proteins to support cellular maintenance and differentiation. While previous work has principally utilized self-organizing models or protein-rich hydrogels for neural culture, the three-dimensional matrix developed here through nanoarchitectonics represents a chemically defined and robust alternative for the in vitro study of neurodevelopment and nervous system disorders.

Modelling the central nervous system: tissue engineering of the cellular microenvironment

With the increasing prevalence of neurodegenerative diseases, improved models of the central nervous system (CNS) will improve our understanding of neurophysiology and pathogenesis, whilst enabling exploration of novel therapeutics. Studies of brain physiology have largely been carried out using in vivo models, ex vivo brain slices or primary cell culture from rodents. Whilst these models have provided great insight into complex interactions between brain cell types, key differences remain between human and rodent brains, such as degree of cortical complexity. Unfortunately, comparative models of human brain tissue are lacking. The development of induced Pluripotent Stem Cells (iPSCs) has accelerated advancement within the field of in vitro tissue modelling. However, despite generating accurate cellular representations of cortical development and disease, two-dimensional (2D) iPSC-derived cultures lack an entire dimension of environmental information on structure, migration, polarity, neuronal circuitry and spatiotemporal organisation of cells. As such, researchers look to tissue engineering in order to develop advanced biomaterials and culture systems capable of providing necessary cues for guiding cell fates, to construct in vitro model systems with increased biological relevance. This review highlights experimental methods for engineering of in vitro culture systems to recapitulate the complexity of the CNS with consideration given to previously unexploited biophysical cues within the cellular microenvironment.

Application of Temporary, Cell-Containing Alginate Microcarriers to Facilitate the Fabrication of Spatially Defined Cell Pockets in 3D Collagen Hydrogels

Mimicking the complexity of natural tissue is a major challenge in the field of tissue engineering. Here, a facile 2-step fabrication method to prepare 3D constructs with distinct regions of high cell concentrations and without the need for elaborate equipment is proposed. The initial incorporation of cells in a sacrificial alginate matrix allows the addition of other, cell relevant biopolymers, such as, collagen to form a spatially confined, interpenetrating network at the microscale. A layered structure at the macroscale can be achieved by incorporating these cell-containing microspheres in thin collagen layers. Cells are locally released by de-gelling the alginate matrix and their attachment to the collagen hydrogel layers has been studied. The use of the murine pre-osteoblast cell line MC3T3-E1 as an example cell line shows that the cells behave differently in their cell migration pattern based on the initial composition of the alginate microspheres.

Tracking the Differentiation Status of Human Neural Stem Cells through Label-Free Raman Spectroscopy and Machine Learning-Based Analysis

The ability to noninvasively monitor stem cells' differentiation is important to stem cell studies. Raman spectroscopy is a non-harmful imaging approach that acquires the cellular biochemical signatures. Herein, we report the first use of label-free Raman spectroscopy to characterize the gradual change during the differentiation process of live human neural stem cells (NSCs) in the in vitro cultures. Raman spectra of 600-1800 cm-1 were measured with human NSC cultures from the undifferentiated stage (NSC-predominant) to the highly differentiated one (neuron-predominant) and subsequently analyzed using various mathematical methods. Hierarchical cluster analysis distinguished two cell types (NSCs and neurons) through the spectra. The subsequently derived differentiation rate matched that measured by immunocytochemistry. The key spectral biomarkers were identified by time-dependent trend analysis and principal component analysis. Furthermore, through machine learning-based analysis, a set of eight spectral data points were found to be highly accurate in classifying cell types and predicting the differentiation rate. The predictive accuracy was the highest using the artificial neural network (ANN) and slightly lowered using the logistic regression model and linear discriminant analysis. In conclusion, label-free Raman spectroscopy with the aid of machine learning analysis can provide the noninvasive classification of cell types at the single-cell level and thus accurately track the human NSC differentiation. A set of eight spectral data points combined with the ANN method were found to be the most efficient and accurate. Establishing this non-harmful and efficient strategy will shed light on the in vivo and clinical studies of NSCs.

Imitating Hypoxia and Tumor Microenvironment with Immune Evasion by Employing Three Dimensional in vitro Cellular Models: Impressive Tool in Drug Discovery

The heterogeneous tumor microenvironment is exceptionally perplexing and not wholly comprehended. Different multifaceted alignments lead to the generation of oxygen destitute situations within the tumor niche that modulate numerous intrinsic tumor microenvironments. Disentangling these communications is vital for scheming practical therapeutic approaches that can successfully decrease tumor allied chemotherapy resistance by utilizing the innate capability of the immune system. Several research groups have concerned with a protruding role for oxygen metabolism along with hypoxia in the immunity of healthy tissue. Hypoxia in addition to hypoxia-inducible factors (HIFs) in the tumor microenvironment plays an important part in tumor progression and endurance. Although numerous hypoxia-focused therapies have shown promising outcomes both in vitro and in vivo these outcomes have not effectively translated into clinical preliminaries. Distinctive cell culture techniques have utilized as an in vitro model for tumor niche along with tumor microenvironment and proficient in more precisely recreating tumor genomic profiles as well as envisaging therapeutic response. To study the dynamics of tumor immune evasion, three-dimensional (3D) cell cultures are more physiologically important to the hypoxic tumor microenvironment. Recent research has revealed new information and insights into our fundamental understanding of immune systems, as well as novel results that have been established as potential therapeutic targets. There are a lot of patented 3D cell culture techniques which will be highlighted in this review. At present notable 3D cell culture procedures in the hypoxic tumor microenvironment, discourse open doors to accommodate both drug repurposing, advancement, and divulgence of new medications and will deliberate the 3D cell culture methods into standard prescription disclosure especially in the field of cancer biology which will be discussing here.

Innovative color jet 3D printing of levetiracetam personalized paediatric preparations

3D printing is a promising technology used in the fabrication of complex oral dosage delivery pharmaceuticals. This study first reports an innovative color jet 3D printing (CJ-3DP) technology to produce colorful cartoon levetiracetam pediatric preparations with high accuracy and reproducibility. For this study, the ideal printing ink consisted of 40% (v/v) isopropanol aqueous solution containing 0.05% (w/w) polyvinylpyrrolidone and 4% (w/w) glycerin, which was satisfied with scale-up of the production. The external and internal spatial structures of the tablets were designed to control the appearance and release, and cartoon tablets with admirable appearances and immediate release characteristics were printed. The dosage model showed a good linear relationship between the model volume and the tablet strength (r > 0.999), which proved the potential of personalized administration. The surface roughness indicated that the appearance of the CJ-3DP tablets was significantly better than the first listed 3D printed drug (Spritam^Ⓡ). Moreover, the scanning electron microscopy and porosity results further showed that the tablets have a structure of loose interior and tight exterior, which could ensure good mechanical properties and rapid dispersion characteristics simultaneously. In conclusion, the innovative CJ-3DP technology can be used to fabricate personalized pediatric preparations for improved compliance. Due to the stable formulation and fabrication process, this technology has the potential in scale-up production.

The Emerging Role of Neuronal Organoid Models in Drug Discovery: Potential Applications and Hurdles to Implementation

The high failure rate of drugs in the clinical pipeline is likely in part the result of inadequate preclinical models, particularly those for neurologic disorders and neurodegenerative disease. Such preclinical animal models often suffer from fundamental species differences and rarely recapitulate all facets of neurologic conditions, whereas conventional two-dimensional (2D) in vitro models fail to capture the three-dimensional spatial organization and cell-to-cell interactions of brain tissue that are presumed to be critical to the function of the central nervous system. Recent studies have suggested that stem cell-derived neuronal organoids are more physiologically relevant than 2D neuronal cultures because of their cytoarchitecture, electrophysiological properties, human origin, and gene expression. Hence there is interest in incorporating such physiologically relevant models into compound screening and lead optimization efforts within drug discovery. However, despite their perceived relevance, compared with previously used preclinical models, little is known regarding their predictive value. In fact, some have been wary to broadly adopt organoid technology for drug discovery because of the low-throughput and tedious generation protocols, inherent variability, and lack of compatible moderate-to-high-throughput screening assays. Consequently, microfluidic platforms, specialized bioreactors, and automated assays have been and are being developed to address these deficits. This mini review provides an overview of the gaps to broader implementation of neuronal organoids in a drug discovery setting as well as emerging technologies that may better enable their utilization. SIGNIFICANCE STATEMENT: Neuronal organoid models offer the potential for a more physiological system in which to study neurological diseases, and efforts are being made to employ them not only in mechanistic studies but also in profiling/screening purposes within drug discovery. In addition to exploring the utility of neuronal organoid models within this context, efforts in the field aim to standardize such models for consistency and adaptation to screening platforms for throughput evaluation. This review covers potential impact of and hurdles to implementation.

Bioactivity Comparison of Electrospun PCL Mats and Liver Extracellular Matrix as Scaffolds for HepG2 Cells

Cells grown on bioactive matrices have immensely advanced many aspects of biomedical research related to drug delivery and tissue engineering. Our main objective was to perform simple evaluation of the structural and biotic qualities of cell scaffolds made of affordable biomaterials for liver cell line (HepG2) cultivation in vitro. In this work the electrospun matrix made of synthetic polyester poly(ε-caprolactone) (PCL) was compared with the natural protein-based extracellular matrix isolated from porcine liver (ECM). Mechanical and structural analysis showed that ECM was about 12 times less resistant to tensile stress while it had significantly larger pore size and twice smaller water contact angle than PCL. Bioactivity assessment included comparison of cell growth and transfection efficiency on cell-seeded scaffolds. Despite the differences in composition and structure between the two respective matrices, the rate of cell spreading and the percentage of transfected cells on both scaffolds were fairly comparable. These results suggest that in an attempt to produce simple, cell carrying structures that adequately simulate the natural scaffold, one can rely on PCL electrospun mats.

Hyaluronic Acid Biomaterials for Central Nervous System Regenerative Medicine

Hyaluronic acid (HA) is a primary component of the brain extracellular matrix and functions through cellular receptors to regulate cell behavior within the central nervous system (CNS). These behaviors, such as migration, proliferation, differentiation, and inflammation contribute to maintenance and homeostasis of the CNS. However, such equilibrium is disrupted following injury or disease leading to significantly altered extracellular matrix milieu and cell functions. This imbalance thereby inhibits inherent homeostatic processes that support critical tissue health and functionality in the CNS. To mitigate the damage sustained by injury/disease, HA-based tissue engineering constructs have been investigated for CNS regenerative medicine applications. HA's effectiveness in tissue healing and regeneration is primarily attributed to its impact on cell signaling and the ease of customizing chemical and mechanical properties. This review focuses on recent findings to highlight the applications of HA-based materials in CNS regenerative medicine.

Electrospun nanofibers in cancer research: from engineering of in vitro 3D cancer models to therapy

Electrospinning is historically related to tissue engineering due to its ability to produce nano-/microscale fibrous materials with mechanical and functional properties that are extremely similar to those of the extracellular matrix of living tissues. The general interest in electrospun fibrous matrices has recently expanded to cancer research both as scaffolds for in vitro cancer modelling and as patches for in vivo therapeutic delivery. In this review, we examine electrospinning by providing a brief description of the process and overview of most materials used in this process, discussing the effect of changing the process parameters on fiber conformations and assemblies. Then, we describe two different applications of electrospinning in service of cancer research: firstly, as three-dimensional (3D) fibrous materials for generating in vitro pre-clinical cancer models; and secondly, as patches encapsulating anticancer agents for in vivo delivery.

A resazurin-based, nondestructive assay for monitoring cell proliferation during a scaffold-based 3D culture process

Development of viable cell estimation method without sacrificing proliferation and functions of cells cultured on regenerative biomaterials is essential for regenerative engineering. Cytotoxicity and depletion of resazurin are critical but often overlooked limitations that hindered applications of resazurin in viable cell estimation. The present work found that cytotoxicity and depletion of resazurin depended on cell concentration, resazurin concentration and resazurin incubation time. A simple strategy which only allowed cells to incubate with resazurin during each measurement was developed to eliminate negative effects of resazurin. This strategy was verified by monitoring proliferation of MC3T3-E1 preosteoblasts on poly(d,l-lactic acid) scaffold during a continuous 3D culture process for up to 21 days, comparing the accuracy with MTT assay which is a destructive assay with high sensitivity and accuracy and commonly used in regenerative engineering and comparing viability, proliferation and differentiation functions of MC3T3-E1, which were treated with/without this strategy for nondestructive evaluation. This method showed comparable linearity of standard curve and characteristics of growth curve to MTT assay. No major negative effects of this method on MC3T3-E1 viability and functions were found. Our work highlighted the importance of the concentration and incubation time of resazurin in designing application-specific nondestructive viability assay and would be helpful in improving the implanted medical devices as well as in regenerative engineering.

Waste Autochthonous Tuscan Olive Leaves (Olea europaea var. Olivastra seggianese) as Antioxidant Source for Biomedicine

Olive leaf extract (OLE) can be obtained as biowaste and is extensively used a food supplement and an over-the-counter drug for its beneficial effects. New studies have investigated OLE concerning the role of oxidative stress in the pathogenesis of vascular disease. This in vitro study aims to evaluate if OLE extracted from the Tuscan Olea europaea protects endothelial cells against oxidative stress generated by reactive oxygen species (ROS).

METHODS

OLE total polyphenols (TPs) were characterized by the Folin-Ciocalteu method. Endothelial cells were grown in conventional cultures (i.e., two-dimensional, 2D) and on a biomaterial scaffold (i.e., three-dimensional, 3D) fabricated via electrospinning. Cell viability and ROS measurement after H₂O₂ insults were performed.

RESULTS

OLE TP content was 23.29 mg GAE/g, and oleuropein was the principal compound. The dose-dependent viability curve highlighted the absence of significant cytotoxic effects at OLE concentrations below 250 µg/mL TPs. By using OLE preconditioning at 100 µg/mL, cell viability decrease was observed, being in 3D lower than in the 2D model. OLE was protective against ROS in both models.

CONCLUSIONS

OLE represents a high-value antioxidant source obtained by biowaste that is interesting for biomedical products. Using a 3D scaffold could be the best predictive model to mimic the physiological conditions of vascular tissue reaction.

Improving the Rate of Translation of Tissue Engineering Products

Over 100 000 research articles and 9000 patents have been published on tissue engineering (TE) in the past 20 years. Yet, very few TE products have made their way to the market during the same period. Experts have proposed a variety of strategies to address the lack of translation of TE products. However, since these proposals are guided by qualitative insights, they are limited in scope and impact. Machine learning is utilized in the current study to analyze the entire body of patents that have been published over the past twenty years and understand patenting trends, topics, areas of application, and exemplifications. This analysis yields surprising and little-known insights about the differences in research priorities and perceptions of innovativeness of tissue engineers in academia and industry, as well as aids to chart true advances in the field during the past twenty years. It is hoped that this analysis and subsequent proposal to improve translational rates of TE products will spur much needed dialogue about this important pursuit.

Injectable peptide hydrogel as intraperitoneal triptolide depot for the treatment of orthotopic hepatocellular carcinoma

Chemotherapy is among the limited choices approved for the treatment of hepatocellular carcinoma (HCC) at intermediate and advanced stages. Preferential and prolonged drug exposure in diseased sites is required to maximize the therapeutic index of the drug. Here, we report an injectable supramolecular peptide hydrogel as an intraperitoneal depot for localized and sustained release of triptolide for the treatment of orthotopic HCC. We chose peptide amphiphile C₁₆-GNNQQNYKD-OH-based nanofibers as gelators and carriers for triptolide. Sustained triptolide release from the hydrogel was achieved over 14 days in vitro, with higher accumulation in and cytotoxicity against human HCC Bel-7402 in comparison with L-02 fetal hepatocytes. After intraperitoneal injection, the hydrogel showed prolonged retention over 13 days and preferential accumulation in the liver, realizing HCC growth inhibition by 99.7 ± 0.1% and animal median survival extension from 19 to 43 days, without causing noticeable pathological changes in the major organs. These results demonstrate that injectable peptide hydrogel can be a potential carrier for localized chemotherapy of HCC.

Decellularization techniques and their applications for the repair and regeneration of the nervous system

A variety of surgical and non-surgical approaches have been used to address the impacts of nervous system injuries, which can lead to either impairment or a complete loss of function for affected patients. The inherent ability of nervous tissues to repair and/or regenerate is dampened due to irreversible changes that occur within the tissue remodeling microenvironment following injury. Specifically, dysregulation of the extracellular matrix (i.e., scarring) has been suggested as one of the major factors that can directly impair normal cell function and could significantly alter the regenerative potential of these tissues. A number of tissue engineering and regenerative medicine-based approaches have been suggested to intervene in the process of remodeling which occurs following injury. Decellularization has become an increasingly popular technique used to obtain acellular scaffolds, and their derivatives (hydrogels, etc.), which retain tissue-specific components, including critical structural and functional proteins. These advantageous characteristics make this approach an intriguing option for creating materials capable of stimulating the sensitive repair mechanisms associated with nervous system injuries. Over the past decade, several diverse decellularization methods have been implemented specifically for nervous system applications in an attempt to carefully remove cellular content while preserving tissue morphology and composition. Each application-based decellularized ECM product requires carefully designed treatments that preserve the unique biochemical signatures associated within each tissue type to stimulate the repair of brain, spinal cord, and peripheral nerve tissues. Herein, we review the decellularization techniques that have been applied to create biomaterials with the potential to promote the repair and regeneration of tissues within the central and peripheral nervous system.

Develop a 3D neurological disease model of human cortical glutamatergic neurons using micropillar-based scaffolds

Establishing an effective three-dimensional (3D) in vitro culture system to better model human neurological diseases is desirable, since the human brain is a 3D structure. Here, we demonstrated the development of a polydimethylsiloxane (PDMS) pillar-based 3D scaffold that mimicked the 3D microenvironment of the brain. We utilized this scaffold for the growth of human cortical glutamatergic neurons that were differentiated from human pluripotent stem cells. In comparison with the 2D culture, we demonstrated that the developed 3D culture promoted the maturation of human cortical glutamatergic neurons by showing significantly more MAP2 and less Ki67 expression. Based on this 3D culture system, we further developed an in vitro disease-like model of traumatic brain injury (TBI), which showed a robust increase of glutamate-release from the neurons, in response to mechanical impacts, recapitulating the critical pathology of TBI. The increased glutamate-release from our 3D culture model was attenuated by the treatment of neural protective drugs, memantine or nimodipine. The established 3D in vitro human neural culture system and TBI-like model may be used to facilitate mechanistic studies and drug screening for neurotrauma or other neurological diseases.