Instant Gelation System as Self-Healable and Printable 3D Cell Culture Bioink Based on Dynamic Covalent Chemistry

The rapid development of additive manufacturing techniques in the field of tissue regeneration offers unprecedented success for artificial tissue and organ fabrication. However, some limitations still remain for current bioinks, such as the compromised cell viability after printing, the low cross-linking efficiency leading to poor printing resolution and speed due to the relatively slow gelation rate, and the requirement of external stimuli for gelation. To address these problems, herein, a biocompatible and printable instant gelation hydrogel system has been developed based on a designed hyperbranched poly(ethylene glycol) (PEG)-based multihydrazide macro-cross-linker (HB-PEG-HDZ) and an aldehyde-functionalized hyaluronic acid (HA-CHO). HB-PEG-HDZ is prepared by the postfunctionalization of hyperbranched PEG-based multivinyl macromer via thiol-ene chemistry. Owing to the high functional group density of HB-PEG-HDZ, the hydrogel can be formed instantly upon mixing the solutions of two components. The reversible cross-linking mechanism between the hydrazide and aldehyde groups endows the hydrogel with shear-thinning and self-healing properties. The minimally toxic components and cross-linking chemistry allow the resulting hydrogel to be a biocompatible niche. Moreover, the fast sol-to-gel transition of the hydrogel, combining all of the advanced characteristics of this platform, protects the cells during the printing procedure, avoids their damage during extrusion, and improves the transplanted cell survival.

Reconfigurable Microphysiological Systems for Modeling Innervation and Multitissue Interactions

Tissue-engineered models continue to experience challenges in delivering structural specificity, nutrient delivery, and heterogenous cellular components, especially for organ-systems that require functional inputs/outputs and have high metabolic requirements, such as the heart. While soft lithography has provided a means to recapitulate complex architectures in the dish, it is plagued with a number of prohibitive shortcomings. Here, concepts from microfluidics, tissue engineering, and layer-by-layer fabrication are applied to develop reconfigurable, inexpensive microphysiological systems that facilitate discrete, 3D cell compartmentalization, and improved nutrient transport. This fabrication technique includes the use of the meniscus pinning effect, photocrosslinkable hydrogels, and a commercially available laser engraver to cut flow paths. The approach is low cost and robust in capabilities to design complex, multilayered systems with the inclusion of instrumentation for real-time manipulation or measures of cell function. In a demonstration of the technology, the hierarchal 3D microenvironment of the cardiac sympathetic nervous system is replicated. Beat rate and neurite ingrowth are assessed on-chip and quantification demonstrates that sympathetic-cardiac coculture increases spontaneous beat rate, while drug-induced increases in beating lead to greater sympathetic innervation. Importantly, these methods may be applied to other organ-systems and have promise for future applications in drug screening, discovery, and personal medicine.

Pumpless microfluidic device with open top cell culture under oscillatory shear stress

Here we developed a 96-well plate-based pumpless microfluidic device to mimic bidirectional oscillatory shear stress experienced by osteoblasts at the endosteal niche located at the interface between bone and bone marrow. The culture device was designed to be high-throughput with 32 open top culture chambers for convenient cell seeding and staining. Mathematical modeling was used to simulate the control of oscillatory shear stress with the peak stress in the range of 0.3 to 50 mPa. Osteoblasts, cultured under oscillatory shear stress, were found to be highly viable and significantly aligned along the direction of flow. The modeling and experimental results demonstrate for the first time that cells can be cultured under controllable oscillatory shear stress in the open top culture chamber and pumpless configurations.

Aberrant Differentiation of Human Pluripotent Stem Cell-Derived Kidney Precursor Cells inside Mouse Vascularized Bioreactors

BACKGROUND

Numerous studies have documented the in vitro differentiation of human pluripotent stem cells (hPSCs) into kidney cells. Fewer studies have followed the fates of such kidney precursor cells (KPCs) inside animals, a more life-like setting. Here, we tested the hypothesis that implanting hPSC-derived KPCs into an in vivo milieu surgically engineered to be highly vascular would enhance their maturation into kidney tissues.

METHODS

3D printed chambers containing KPCs were implanted into the thighs of adult immunodeficient mice. In some chambers, an arterial and venous flow-through (AVFT) was surgically fashioned. After 3 weeks and 3 months, implants were studied by histology, using qualitative and quantitative methods.

RESULTS

After 3 weeks, chambers containing AVFTs were richer in small vessels than contralateral chambers without AVFTs. Glomeruli with capillary loops and diverse types of tubules were detected in all chambers. At 3 months, chambers contained only rudimentary tubules and glomeruli that appeared avascular. In chambers with AVFTs, prominent areas of muscle-like cells were also detected near tubules and the abnormal tissues immunostained for transforming growth factor β1. These features have similarities to renal dysplasia, a typical histological signature of human congenital kidney malformations.

CONCLUSIONS

This study urges a note of caution regarding the in vivo fates of hPSC-derived kidney precursors, with pathological differentiation appearing to follow a period of increased vascularity.

Homogenization of initial cell distribution by secondary flow of medium improves cell culture efficiency

Homogenization of the initial cell distribution is essential for effective cell development. However, there are few previous reports on efficient cell seeding methods, even though the initial cell distribution has a large effect on cell proliferation. Dense cell regions have an inverse impact on cell development, known as contact inhibition. In this study, we developed a method to homogenize the cell seeding density using secondary flow, or Ekman transportation, induced by orbital movement of the culture dish. We developed an orbital shaker device that can stir the medium in a 35-mm culture dish by shaking the dish along a circular orbit with 2 mm of eccentricity. The distribution of cells in the culture dish can be controlled by the rotational speed of the orbital shaker, enabling dispersion of the initial cell distribution. The experimental results indicated that the cell density became most homogeneous at 61 rpm. We further evaluated the cell proliferation after homogenization of the initial cell density at 61 rpm. The results revealed 36% higher proliferation for the stirred samples compared with the non-stirred control samples. The present findings indicate that homogenization of the initial cell density by Ekman transportation contributes to the achievement of higher cell proliferation.

A Microfluidic Single-Cell Cloning (SCC) Device for the Generation of Monoclonal Cells

Single-cell cloning (SCC) is a critical step in generating monoclonal cell lines, which are widely used as in vitro models and for producing proteins with high reproducibility for research and the production of therapeutic drugs. In monoclonal cell line generation, the development time can be shortened by validating the monoclonality of the cloned cells. However, the validation process currently requires specialized equipment that is not readily available in general biology laboratories. Here, we report a disposable SCC device, in which single cells can be isolated, validated, and expanded to form monoclonal cell colonies using conventional micropipettes and microscopes. The monoclonal cells can be selectively transferred from the SCC chip to conventional culture plates, using a tissue puncher. Using the device, we demonstrated that monoclonal colonies of actin-GFP (green fluorescent protein) plasmid-transfected A549 cells could be formed in the device within nine days and subsequently transferred to wells in plates for further expansion. This approach offers a cost-effective alternative to the use of specialized equipment for monoclonal cell generation.

Simultaneous Isolation and Culture of Atrial Myocytes, Ventricular Myocytes, and Non-Myocytes from an Adult Mouse Heart

The isolation and culturing of cardiac myocytes from mice has been essential for furthering the understanding of cardiac physiology and pathophysiology. While isolating myocytes from neonatal mouse hearts is relatively straightforward, myocytes from the adult murine heart are preferred. This is because compared to neonatal cells, adult myocytes more accurately recapitulate cell function as it occurs in the adult heart in vivo. However, it is technically difficult to isolate adult mouse cardiac myocytes in the necessary quantities and viability, which contributes to an experimental impasse. Furthermore, published procedures are specific for the isolation of either atrial or ventricular myocytes at the expense of atrial and ventricular non-myocyte cells. Described here is a detailed method for isolating both atrial and ventricular cardiac myocytes, along with atrial and ventricular non-myocytes, simultaneously from a single mouse heart. Also provided are the details for optimal cell-specific culturing methods, which enhance cell viability and function. This protocol aims not only to expedite the process of adult murine cardiac cell isolation, but also to increase the yield and viability of cells for investigations of atrial and ventricular cardiac cells.

Cell Adhesion Molecule 1 Contributes to Cell Survival in Crowded Epithelial Monolayers

When epithelial cells in vivo are stimulated to proliferate, they crowd and often grow in height. These processes are likely to implicate dynamic interactions among lateral membranous proteins, such as cell adhesion molecule 1 (CADM1), an immunoglobulin superfamily member. Pulmonary epithelial cell lines that express CADM1, named NCI-H441 and RLE-6TN, were grown to become overconfluent in the polarized 2D culture system, and were examined for the expression of CADM1. Western analyses showed that the CADM1 expression levels increased gradually up to 3 times in a cell density-dependent manner. Confocal microscopic observations revealed dense immunostaining for CADM1 on the lateral membrane. In the overconfluent monolayers, CADM1 knockdown was achieved by two methods using CADM1-targeting siRNA and an anti-CADM1 neutralizing antibody. Antibody treatment experiments were also done on 6 other epithelial cell lines expressing CADM1. The CADM1 expression levels were reduced roughly by half, in association with cell height decrease by half in 3 lines. TUNEL assays revealed that the CADM1 knockdown increased the proportion of TUNEL-positive apoptotic cells approximately 10 folds. Increased expression of CADM1 appeared to contribute to cell survival in crowded epithelial monolayers.

Scaffolds of PCL combined to bioglass: synthesis, characterization and biological performance

Biomaterials may be useful in filling lost bone portions in order to restore balance and improve bone regeneration. The objective of this study was to produce polycaprolactone (PCL) membranes combined with two types of bioglass (Sol-Gel and melt-quenched) and determine their physical and biological properties. Membranes were produced through electrospinning. This study presented three experimental groups: pure PCL membranes, PCL-Melt-Bioglass and PCL-Sol-gel-Bioglass. Membranes were characterized using Scanning Electron Microscopy, Fourier Transform Infrared Spectrophotometry (FTIR), Energy-Dispersive Spectroscopy and Zeta Potential. The following in vitro tests were performed: MTT assay, alkaline phosphatase activity, total protein content and mineralization nodules. Twenty-four male rats were used to observe biological performance through radiographic, fracture energy, histological and histomorphometric analyses. The physical and chemical analysis results showed success in manufacturing bioactive membranes which significantly enhanced cell viability and osteoblast differentiation. The new formed bone from the in vivo experiment was similar to that observed in the control group. In conclusion, the electrospinning enabled preparing PCL membranes with bioglass incorporated into the structure and onto the surface of PCL fibers. The microstructure of the PCL membranes was influenced by the bioglass production method. Both bioglasses seem to be promising biomaterials to improve bone tissue regeneration when incorporated into PCL.

Dynamic Environmental Control in Microfluidic Single-Cell Cultivations: From Concepts to Applications

Microfluidic single-cell cultivation (MSCC) is an emerging field within fundamental as well as applied biology. During the last years, most MSCCs were performed at constant environmental conditions. Recently, MSCC at oscillating and dynamic environmental conditions has started to gain significant interest in the research community for the investigation of cellular behavior. Herein, an overview of this topic is given and microfluidic concepts that enable oscillating and dynamic control of environmental conditions with a focus on medium conditions are discussed, and their application in single-cell research for the cultivation of both mammalian and microbial cell systems is demonstrated. Furthermore, perspectives for performing MSCC at complex dynamic environmental profiles of single parameters and multiparameters (e.g., pH and O₂ ) in amplitude and time are discussed. The technical progress in this field provides completely new experimental approaches and lays the foundation for systematic analysis of cellular metabolism at fluctuating environments.

Micropatterned Biphasic Nanocomposite Platform for Maintaining Chondrocyte Morphology

One major limitation hindering the translation of in vitro osteoarthritis research into clinical disease-modifying therapies is that chondrocytes rapidly spread and dedifferentiate under standard monolayer conditions. Current strategies to maintain rounded morphologies of chondrocytes in culture either unnaturally restrict adhesion and place chondrocytes in an excessively stiff mechanical environment or are impractical for use in many applications. To address the limitations of current techniques, we have developed a unique composite thin-film cell culture platform, the CellWell, to model articular cartilage that utilizes micropatterned hemispheroidal wells, precisely sized to fit individual cells (12-18 μm diameters), to promote physiologically spheroidal chondrocyte morphologies while maintaining compatibility with standard cell culture and analytical techniques. CellWells were constructed of 15-μm-thick 5% agarose films embedded with electrospun poly(vinyl alcohol) (PVA) nanofibers. Transmission electron microscope (TEM) images of PVA nanofibers revealed a mean diameter of 60.9 ± 24 nm, closely matching the observed 53.8 ± 29 nm mean diameter of human ankle collagen II fibers. Using AFM nanoindentation, CellWells were found to have compressive moduli of 158 ± 0.60 kPa at 15 μm/s indentation, closely matching published stiffness values of the native pericellular matrix. Primary human articular chondrocytes taken from ankle cartilage were seeded in CellWells and assessed at 24 h. Chondrocytes maintained their rounded morphology in CellWells (mean aspect ratio of 0.87 ± 0.1 vs three-dimensional (3D) control [0.86 ± 0.1]) more effectively than those seeded under standard conditions (0.65 ± 0.3), with average viability of >85%. The CellWell's design, with open, hemispheroidal wells in a thin film substrate of physiological stiffness, combines the practical advantages of two-dimensional (2D) culture systems with the physiological advantages of 3D systems. Through its ease of use and ability to maintain the physiological morphology of chondrocytes, we expect that the CellWell will enhance the clinical translatability of future studies conducted using this culture platform.

Adjustable and Versatile 3D Tumor Spheroid Culture Platform with Interfacial Elastomeric Wells

Three-dimensional (3D) cell culture platforms have recently received a great deal of attention, as these systems are able to recapitulate the in vivo microenvironment of tissues or tumors. Herein, we describe adjustable and versatile elastomeric well structures for spheroid formation and their use for in situ analyses as a tunable 3D cell culture platform. Elastomeric spherical wells are fabricated using a one-step interfacial reaction between aqueous droplets on immiscible liquid polydimethylsiloxane (PDMS) without any template or expensive equipment. Because of their differing surface tensions, spherical wells are spontaneously formed on liquid PDMS with various sizes and curvatures that are easily controlled. Using arrays of these optimized wells, single tumor spheroids within each well were successfully formed at high efficiency (up to 97%) by coculturing tumor cells and fibroblasts to reflect the complex microenvironment of cancer tissue. Moreover, the tumor spheroids formed within the interfacial wells were directly applied for observing drug responses and monitoring reactive oxygen species (ROS) to investigate tumor cell responses to drugs or their 3D microenvironment. We believe that our proposed platform provides a significant contribution to the multimodal analyses of anticancer therapeutics and the tumor microenvironment.

An Interpenetrating Alginate/Gelatin Network for Three-Dimensional (3D) Cell Cultures and Organ Bioprinting

Crosslinking is an effective way to improve the physiochemical and biochemical properties of hydrogels. In this study, we describe an interpenetrating polymer network (IPN) of alginate/gelatin hydrogels (i.e., A-G-IPN) in which cells can be encapsulated for in vitro three-dimensional (3D) cultures and organ bioprinting. A double crosslinking model, i.e., using Ca²⁺ to crosslink alginate molecules and transglutaminase (TG) to crosslink gelatin molecules, is exploited to improve the physiochemical, such as water holding capacity, hardness and structural integrity, and biochemical properties, such as cytocompatibility, of the alginate/gelatin hydrogels. For the sake of convenience, the individual ionic (i.e., only treatment with Ca²⁺) or enzymatic (i.e., only treatment with TG) crosslinked alginate/gelatin hydrogels are referred as alginate-semi-IPN (i.e., A-semi-IPN) or gelatin-semi-IPN (i.e., G-semi-IPN), respectively. Tunable physiochemical and biochemical properties of the hydrogels have been obtained by changing the crosslinking sequences and polymer concentrations. Cytocompatibilities of the obtained hydrogels are evaluated through in vitro 3D cell cultures and bioprinting. The double crosslinked A-G-IPN hydrogel is a promising candidate for a wide range of biomedical applications, including bioartificial organ manufacturing, high-throughput drug screening, and pathological mechanism analyses.

Concentration-response evaluation of ToxCast compounds for multivariate activity patterns of neural network function

The US Environmental Protection Agency's ToxCast program has generated toxicity data for thousands of chemicals but does not adequately assess potential neurotoxicity. Networks of neurons grown on microelectrode arrays (MEAs) offer an efficient approach to screen compounds for neuroactivity and distinguish between compound effects on firing, bursting, and connectivity patterns. Previously, single concentrations of the ToxCast Phase II library were screened for effects on mean firing rate (MFR) in rat primary cortical networks. Here, we expand this approach by retesting 384 of those compounds (including 222 active in the previous screen) in concentration-response across 43 network activity parameters to evaluate neural network function. Using hierarchical clustering and machine learning methods on the full suite of chemical-parameter response data, we identified 15 network activity parameters crucial in characterizing activity of 237 compounds that were response actives ("hits"). Recognized neurotoxic compounds in this network function assay were often more potent compared to other ToxCast assays. Of these chemical-parameter responses, we identified three k-means clusters of chemical-parameter activity (i.e., multivariate MEA response patterns). Next, we evaluated the MEA clusters for enrichment of chemical features using a subset of ToxPrint chemotypes, revealing chemical structural features that distinguished the MEA clusters. Finally, we assessed distribution of neurotoxicants with known pharmacology within the clusters and found that compounds segregated differentially. Collectively, these results demonstrate that multivariate MEA activity patterns can efficiently screen for diverse chemical activities relevant to neurotoxicity, and that response patterns may have predictive value related to chemical structural features.

Simple Fabrication of Flexible Biosensor Arrays Using Direct Writing for Multianalyte Measurement from Human Astrocytes

Simultaneous measurements of glucose, lactate, and neurotransmitters (e.g., glutamate) in cell culture over hours and days can provide a more dynamic and longitudinal perspective on ways neural cells respond to various drugs and environmental cues. Compared with conventional microfabrication techniques, direct writing of conductive ink is cheaper, faster, and customizable, which allows rapid iteration for different applications. Using a simple direct writing technique, we printed biosensor arrays onto cell culture dishes, flexible laminate, and glass to enable multianalyte monitoring. The ink was a composite of PEDOT:PSS conductive polymer, silicone, activated carbon, and Pt microparticles. We applied 0.5% Nafion to the biosensors for selectivity and functionalized them with oxidase enzymes. We characterized biosensors in phosphate-buffered saline and in cell culture medium supplemented with fetal bovine serum. The biosensor arrays measured glucose, lactate, and glutamate simultaneously and continued to function after incubation in cell culture at 37 °C for up to 2 days. We cultured primary human astrocytes on top of the biosensor arrays and placed arrays into astrocyte cultures. The biosensors simultaneously measured glucose, glutamate, and lactate from astrocyte cultures. Direct writing can be integrated with microfluidic organ-on-a-chip platforms or as part of a smart culture dish system. Because we print extrudable and flexible components, sensing elements can be printed on any 3D or flexible substrate.

Comparative study of the production of soluble factors in human placenta-derived mesenchymal stromal/stem cells grown in adherent conditions or as aggregates in a catheter-like device

Different approaches have been studied in both preclinical and clinical settings to develop cell-based therapies and/or engineered cell-based therapies to better integrate grafts with the host. In these techniques, much attention is addressed to the use of adult stem cells such as mesenchymal stem cells (MSCs), but identifying and obtaining sufficient numbers of therapeutic cells, and the right route of administration, is often a challenge. In this study, we tested the feasibility of encapsulating human amnion-derived MSCs (hAMSCs) in a semipermeable and biocompatible fiber as a new approach for regenerative medicine. Our data showed that hAMSCs aggregated in the device constitutes an effective system for enhancing, or at least for maintaining, the paracrine activity of these cells in order to better promote tissue regeneration in an immune isolated state. In our new experimental approach, the hAMSCs retained their therapeutic potential, as shown by both the production of specific immunomodulatory/angiogenic factors and immunomodulatory and angiogenic ability observed in vitro. Unlike cell infusion methods, the use of encapsulated-cells leads to minimally invasive approaches, avoiding a direct interaction with the host. Therefore, the potentiality of an allograft or xenograft without the need for immunosuppression, and the lack of tumorigenesis is very intriguing.

Adult stem cell response to doped bioactive borate glass

Bioactive glasses have transformed healthcare due to their versatility. Bioactive borate glass, in particular, has shown remarkable healing properties for both hard and soft tissues. Incorporating dopants into the composition of bioactive glass helps to control mechanical properties, and it increases their usefulness for clinical applications. Using a bioactive borate glass, 13-93B3 (B3), we investigated eleven dopants on the viability and migration potential of adipose stem cells (ASCs), a therapeutic source of cells used in tissue engineering and cell therapy. Our results show that under standard cell culture conditions, only Cu-doped B3 decreased cell viability, while only Y-doped B3 attracted ASCs as it dissolved in cell culture media. Using a transwell invasion assay, priming ASCs with Co, Fe, Ga, I, Sr, or Zn-doped B3 increased their homing capacity. Because there is widespread interest in optimizing and enhancing the homing efficiency of ASCs and other therapeutic cells, we then tested if priming bone marrow mesenchymal stem cells (BMSCs) with dopants also increased their homing capacity. In the case of BMSCs, there was a significant increase in invasion when cells were primed with any of the doped-B3 glasses. This work shows that incorporating dopants into borate glasses can provide a platform for a safe and efficient method that stimulates endogenous cells and healing mechanisms.

An Update on the Progress of Isolation, Culture, Storage, and Clinical Application of Human Bone Marrow Mesenchymal Stem/Stromal Cells

Bone marrow mesenchymal stem/stromal cells (BMSCs), which are known as multipotent cells, are widely used in the treatment of various diseases via their self-renewable, differentiation, and immunomodulatory properties. In-vitro and in-vivo studies have supported the understanding mechanisms, safety, and efficacy of BMSCs therapy in clinical applications. The number of clinical trials in phase I/II is accelerating; however, they are limited in the size of subjects, regulations, and standards for the preparation and transportation and administration of BMSCs, leading to inconsistency in the input and outcome of the therapy. Based on the International Society for Cellular Therapy guidelines, the characterization, isolation, cultivation, differentiation, and applications can be optimized and standardized, which are compliant with good manufacturing practice requirements to produce clinical-grade preparation of BMSCs. This review highlights and updates on the progress of production, as well as provides further challenges in the studies of BMSCs, for the approval of BMSCs widely in clinical application.

Bioreactor for mobilization of mesenchymal stem/stromal cells into scaffolds under mechanical stimulation: Preliminary results

Introduction

Articular cartilage (AC) is a viscoelastic tissue with a limited regenerative capability because of the lack of vasculature. Mechanical stimulation contributes to the homeostasis of functional AC since it promotes the delivery of nutrients, cytokines and growth factors between the distant chondrocytes. We hypothesized that biomechanical stimulation might enhance mobilization of endogenous mesenchymal stem/stromal cells (MSCs) from neighboring niches as the bone marrow.

Aim

This study aimed to introduce a bioreactor for inducing mobilization of MSCs from one compartment to another above by mechanical stimulation in vitro.

Methods

A novel mechanical system for evaluating mobilization of cells in a 3D context in vitro is presented. The system consists of a compression bioreactor able to induce loading on hydrogel-based scaffolds, custom-made software for settings management and data recording, and image based biological evaluation. Intermittent load was applied under a periodic regime with frequency of 0.3 Hz and unload phases of 10 seconds each 180 cycles over 24 hours. The mechanical stimulation acted on an alginate scaffold and a cell reservoir containing MSCs below it. The dynamic compression exerted amplitude of 200 μm as 10% strain regarding the original height of the scaffold.

Results

The bioreactor was able to stimulate the scaffolds and the cells for 24.4 (±1.7) hours, exerting compression with vertical displacements of 185.8 (±17.8) μm and a force-amplitude of 1.87 (±1.37; min 0.31, max 4.42) N. Our results suggest that continuous mechanical stimulation hampered the viability of the cells located at the cell reservoir when comparing to intermittent mechanical stimulation (34.4 ± 2.0% vs. 66.8 ± 5.9%, respectively).

Functionalizing alginate scaffolds with laminin-521 (LN521) seemed to enhance the mobilization of cells from 48 (±21) to 194 (±39) cells/mm³ after applying intermittent mechanical loading.

Conclusion

The bioreactor presented here was able to provide mechanical stimulation that seemed to induce the mobilization of MSCs into LN521-alginate scaffolds under an intermittent loading regime.

Development of Mammalian Cell Perfusion Cultures at Lab Scale: From Orbitally Shaken Tubes to Benchtop Bioreactors

This chapter introduces the necessary concepts to develop mammalian cell perfusion cultures for the expression of therapeutic proteins at lab scale. We highlight the operation of the orbitally shaken tubes and of a classical glass vessel reactor system coupled to an external alternating tangential flow (ATF) device. Two different experiments can be performed in the shake-tube system: (1) the VCD_max experiment exploring the maximum achievable viable cell density at a given medium exchange rate and (2) the VCD_SS experiment for the prediction of process performance at constant viable cell density and a given medium exchange rate for the design of the benchtop bioreactor process. In addition, the operation of the benchtop system is discussed containing start-up and control procedures for a long-term production run.

The MAPHEUS module CellFix for studying the influence of altered gravity on the physiology of single cells

Gravity is the only constant stimulus during the evolution of life. To investigate the impact of the absence of gravity on living systems, their molecular and morphological status has to be studied under microgravity conditions. The experiment unit CellFix was developed in order to provide the possibility of exposure and chemical fixation of small biological systems, such as neurons, stem cells, small animals, yeast cultures, plants, etc., at dedicated time points during a sounding rocket flight. The current version of CellFix consists of two culture bags containing cell cultures in a temperature-controlled pressure vessel. The biosystems in the culture bags can be fixed by pumping the fixative [e.g., paraformaldehyde (PFA), methanol, RNAlater, or others] from a connected bag into the cell suspension. The mechatronic basis of the experiment unit is constructed from compartments of the shelf parts. Open source microcontroller systems (Arduino) or gear pumps, accumulators, etc., from the model making sector are affordable and reliable components to build up an experiment on an unmanned space mission such as a sounding rocket flight. Also, new technologies such as fused deposition modeling were used to construct structures and brackets, which were tested successfully in environmental tests and real space flights (MAPHEUS 7 and 8 sounding rocket missions). In combination with the possibility to handle the experiment as a late access insert in a standardized rocket compartment, CellFix provides a multiusable experiment unit for performing life science experiments in space.

Methods and Process Optimization for Large-Scale CAR T Expansion Using the G-Rex Cell Culture Platform

The G-Rex cell culture platform is based on a gas-permeable membrane technology that provides numerous advantages over other systems. Conventional bioreactor platform technologies developed for large scale mammalian cell expansion are typically constrained by the mechanics of delivering oxygen to an expanding cell population. These systems often utilize complex mechanisms to enhance oxygen delivery, such as stirring, rocking, or perfusion, which adds to expense and increases their overall risk of failure. On the other hand, G-Rex gas-permeable membrane-based bioreactors provide a more physiologic environment and avoid the risk and cost associated with more complex systems. The result is a more robust, interacting cell population established through unlimited oxygen and nutrients that are available on demand. By removing the need to actively deliver oxygen, these bioreactors can hold larger medium volumes (more nutrients) which allows the cells to reach a maximum density without complexity or need for media exchange. This platform approach is scaled to meet the needs of research through commercial production with a direct, linear correlation between small and large devices. In the G-Rex platform, examples of cell expansion (9-14 day duration) include; CAR-T cells, which have atypical harvest density of 20-30 × 10⁶/cm² (or 2-3 × 10⁹ cells in a 100 cm² device); NK cells, which have a typical harvest density of 20-30 × 10⁶/cm² (or 2-3 × 10⁹ cells in a 100 cm² device) and numerous other cell types that proliferate without the need for intervention or complex processes normally associated with large scale culture. Here we describe the methods and concepts used to optimize expansion of various cell types in the static G-Rex bioreactor platform.

In Vitro Culture of Cryptosporidium parvum Using Hollow Fiber Bioreactor: Applications for Simultaneous Pharmacokinetic and Pharmacodynamic Evaluation of Test Compounds

Hollow fiber technology is a powerful tool for the culture of difficult-to-grow cells. Cryptosporidium parvum has a multistage sexual and asexual life cycle that has proved difficult to culture by conventional in vitro culture methods. Here, we describe a method utilizing a hollow fiber bioreactor for the continuous in vitro growth of C. parvum that produces sexual and asexual stages. The method enables the evaluation of potential therapeutic compounds under conditions that mirror the dynamic conditions found in the gut facilitating preliminary pharmacokinetic and pharmacodynamic data to be obtained.

A standalone bioreactor system to deliver compressive load under perfusion flow to hBMSC-seeded 3D chitosan-graphene templates

The availability of engineered biological tissues holds great potential for both clinical applications and basic research in a life science laboratory. A prototype standalone perfusion/compression bioreactor system was proposed to address the osteogenic commitment of stem cells seeded onboard of 3D chitosan-graphene (CHT/G) templates. Testing involved the coordinated administration of a 1 mL/min medium flow rate together with dynamic compression (1% strain at 1 Hz; applied twice daily for 30 min) for one week. When compared to traditional static culture conditions, the application of perfusion and compression stimuli to human bone marrow stem cells using the 3D CHT/G template scaffold induced a sizable effect. After using the dynamic culture protocol, there was evidence of a larger number of viable cells within the inner core of the scaffold and of enhanced extracellular matrix mineralization. These observations show that our novel device would be suitable for addressing and investigating the osteogenic phenotype commitment of stem cells, for both potential clinical applications and basic research.

A handy method to remove bacterial contamination from fungal cultures

Contamination control and removal are very important technical aspects of microbiological research. Bacterial contamination is very common in fungal cultures. Currently, the commonly used approach for inhibiting bacteria is antibiotic treatment; however, there are drawbacks to using antibiotics, including incomplete removal, limited antibacterial spectra, tendency toward recontamination, effects to fungal strains, and potential risks to the environment. Therefore, in the present work, we developed a new method for bacterial removal from fungi cultured on solid medium, the Cabin-Sequestering (CS) method, based on the different culture characteristics between fungi and bacteria. First, 3–5 mm round or square holes (the “cabin”) are excavated on a solid medium plate. The fungal strain containing possible bacterial contamination is inoculated into the cabin. The cabin is then covered with a sterilized coverslip, followed by incubation at the appropriate temperature. After 7–10 days of culturing, fungal hyphae grow out along the edge of the coverslip; however, the contaminating bacteria cannot pass through the space formed between the medium and the coverslip and, thus, remain in the cabin. The newly grown fungal hyphae around the coverslip are re-inoculated into fresh culture plates, where they form bacteria-free fungal colonies. The CS method is easy handling, with a short experimental cycle and rare recontamination. When necessary, it can also be used in combination with antibiotics in bacterial removal operations.