A simulated microgravity-oriented AIE probe-ECM hydrogel-integrated chip for cell culture and superoxide anion radical detection

Human space activities have been continuously increasing. Astronauts experiencing spaceflight are faced with health problems caused by special space environments such as microgravity, and the investigation of cell injury is fundamental. The development of a platform capable of cell culture and injury detection is the prerequisite for the investigation. Constructing a platform suitable for special conditions in space life science research is the key issue. The ground-based investigation is an indispensable part of the research. Accordingly, a simulated microgravity (SMG)-oriented integrated chip platform capable of 3D cell culture and in situ visual detection of superoxide anion radical (O2•-) is developed. SMG can cause oxidative stress in human cells, and O2•- is one of the signaling molecules. Thus, a O2•--responsive aggregation-induced emission (AIE) probe is designed, which shows high selectivity and sensitivity to O2•-. Moreover, the probe exhibits abilities of long-term and wash-free staining to cells due to the AIE behavior, which is precious for space cell imaging. Meanwhile, a chip with a high-aspect-ratio chamber for adequate medium storage for the lack of the perfusion system during the SMG experiment and a cell culture chamber which can integrate the extracellular matrix (ECM) hydrogel for the bioinspired 3D cell culture is fabricated. In addition, a porous membrane is introduced between the chambers to prevent the hydrogel from separating during the SMG experiment. The afforded AIE probe-ECM hydrogel-integrated chip can achieve 3D culturing of U87-MG cells and in situ fluorescent detection of endogenous O2•- in the cells after long-term staining under SMG. The chip provides a powerful and potential platform for ground-based investigation in space life science and biomedical research.

Biocompatibility characterisation of CMOS-based Lab-on-Chip electrochemical sensors for in vitro cancer cell culture applications

Lab-on-Chip electrochemical sensors, such as Ion-Sensitive Field-Effect Transistors (ISFETs), are being developed for use in point-of-care diagnostics, such as pH detection of tumour microenvironments, due to their integration with standard Complementary Metal Oxide Semiconductor (CMOS) technology. With this approach, the passivation of the CMOS process is used as a sensing layer to minimise post-processing, and Silicon Nitride (Si3N4) is the most common material at the microchip surface. ISFETs have the potential to be used for cell-based assays however, there is a poor understanding of the biocompatibility of microchip surfaces. Here, we quantitatively evaluated cell adhesion, morphogenesis, proliferation and mechano-responsiveness of both normal and cancer cells cultured on a Si3N4, sensor surface. We demonstrate that both normal and cancer cell adhesion decreased on Si3N4. Activation of the mechano-responsive transcription regulators, YAP/TAZ, are significantly decreased in cancer cells on Si3N4 in comparison to standard cell culture plastic, whilst proliferation marker, Ki67, expression markedly increased. Non-tumorigenic cells on chip showed less sensitivity to culture on Si3N4 than cancer cells. Treatment with extracellular matrix components increased cell adhesion in normal and cancer cell cultures, surpassing the adhesiveness of plastic alone. Moreover, poly-l-ornithine and laminin treatment restored YAP/TAZ levels in both non-tumorigenic and cancer cells to levels comparable to those observed on plastic. Thus, engineering the electrochemical sensor surface with treatments will provide a more physiologically relevant environment for future cell-based assay development on chip.

Diffusion-based culture and real-time impedance monitoring of tumor spheroids in hydrogel microwells of a suspended membrane under microfluidic conditions

Tumor spheroids are widely studied for in vitro modeling of tumor growth and responses to anticancer drugs. However, current methods are mostly limited to static and perfusion-based cultures, which can be improved by more accurately mimicking pathological conditions. Here, we developed a diffusion-based dynamic culture system for tumor spheroids studies using a thin membrane of hydrogel microwells and a microfluidic device. This allows for effective exchange of nutrients and metabolites between the tumors and the culture medium flowing underneath, resulting in uniform tumor spheroids. To monitor the growth and drug response of the spheroids in real-time, we performed spectroscopic analyses of the system's impedance, demonstrating a close correlation between the tumor size and the resistance and capacitance of the system. Our results also indicate an enhanced drug effect on the tumor spheroids in the presence of a low AC electric field, suggesting a weakening mechanism of the spheroids induced by external perturbation.

Bipolar electrochemical growth of conductive microwires for cancer spheroid integration: a step forward in conductive biological circuitry

The field of bioelectronics is developing exponentially. There is now a drive to interface electronics with biology for the development of new technologies to improve our understanding of electrical forces in biology. This builds on our recently published work in which we show wireless electrochemistry could be used to grow bioelectronic functional circuitry in 2D cell layers. To date our ability to merge electronics with in situ with biology is 3D limited. In this study, we aimed to further develop the wireless electrochemical approach for the self-assembly of microwires in situ with custom-designed and fabricated 3D cancer spheroids. Unlike traditional electrochemical methods that rely on direct electrical connections to induce currents, our technique utilises bipolar electrodes that operate independently of physical wired connections. These electrodes enable redox reactions through the application of an external electric field. Specifically, feeder electrodes connected to a power supply generate an electric field, while the bipolar electrodes, not physically connected to the feeder electrodes, facilitate the reduction of silver ions from the solution. This process occurs upon applying a voltage across the feeder electrodes, resulting in the formation of self-assembled microwires between the cancer spheroids.Thereby, creating interlinked bioelectronic circuitry with cancer spheroids. We demonstrate that a direct current was needed to stimulate the growth of conductive microwires in the presence of cell spheroids. Microwire growth was successful when using 50 V (0.5 kV/cm) of DC applied to a single spheroid of approximately 800 µm in diameter but could not be achieved with alternating currents. This represents the first proof of the concept of using wireless electrochemistry to grow conductive structures with 3D mammalian cell spheroids.

Proliferation of SH-SY5Y neuroblastoma cells on confined spaces

BACKGROUND

Microfluidics offers precise drug delivery and continuous monitoring of cell functions, which is crucial for studying the effects of toxins and drugs. Ensuring proper cell growth in these space-constrained systems is essential for obtaining consistent results comparable to standard Petri dishes.

NEW METHOD

We investigated the proliferation of SH-SY5Y cells on circular polycarbonate chambers with varying surface areas. SH-SY5Y cells were chosen for their relevance in neurodegenerative disease research.

RESULTS

Our study demonstrates a correlation between the chamber surface area and SH-SY5Y cell growth rates. Cells cultured in chambers larger than 10 mm in diameter exhibited growth comparable to standard 60-mm dishes. In contrast, smaller chambers significantly impeded growth, even at identical seeding densities. Similar patterns were observed for HeLaGFP cells, while 16HBE14σ cells proliferated efficiently regardless of chamber size. Additionally, SH-SY5Y cells were studied in a 12-mm diameter sealed chamber to assess growth under restricted gas exchange conditions.

COMPARISON WITH EXISTING METHODS

Our findings underscore the limitations of small chamber sizes in microfluidic systems for SH-SY5Y cells, an issue not typically addressed by conventional methods.

CONCLUSIONS

SH-SY5Y cell growth is highly sensitive to spatial constraints, with markedly reduced proliferation in chambers smaller than 10 mm. This highlights the need to carefully consider chamber size in microfluidic experiments to achieve cell growth rates comparable to standard culture dishes. The study also shows that while SH-SY5Y and HeLaGFP cells are affected by chamber size, 16HBE14σ cells are not. These insights are vital for designing effective microfluidic systems for bioengineering research.

Evaluation of various membranes at different fluxes to enable large-volume single-use perfusion bioreactors

The growing demand for biological therapeutics has increased interest in large-volume perfusion bioreactors, but the operation and scalability of perfusion membranes remain a challenge. This study evaluates perfusion cell culture performance and monoclonal antibody (mAb) productivity at various membrane fluxes (1.5-5 LMH), utilizing polyvinylidene difluoride (PVDF), polyethersulfone (PES), or polysulfone (PS) membranes in tangential flow filtration mode. At low flux, culture with PVDF membrane maintained higher cell culture growth, permeate titer (1.06-1.34 g/L) and sieving coefficients (≥83%) but showed lower permeate volumetric throughput and higher transmembrane pressure (TMP) (>1.50 psi) in the later part of the run compared to cultures with PES and PS membrane. However, as permeate flux increased, the total mass of product decreased by around 30% for cultures with PVDF membrane, while it remained consistent with PES and PS membrane, and at the highest flux studied, PES membrane generated 12% more product than PVDF membrane. This highlights that membrane selection for large-volume perfusion bioreactors depends on the productivity and permeate flux required. Since operating large-volume perfusion bioreactors at low flux would require several cell retention devices and a complex setup, PVDF membranes are suitable for low-volume operations at low fluxes whereas PES membranes can be a desirable alternative for large-volume higher demand products at higher fluxes.

Reconfigurable Hanging Drop Microarray Platform for On-Demand Preparation and Analysis of Spheroid Array

In response to the increasing demand for spheroid-based cancer research, the importance of developing integrated platforms that can simultaneously facilitate high-throughput spheroid production and multiplexed analysis is emphasized. In addition, the understanding of how the size and cellular composition of tumors directly influence their internal structures and functionalities underlines the critical need to produce spheroids of diverse sizes and compositions on a large scale. To address this rising demand, this work presents a configurable and linkable in vitro three-dimensional (3D) cell culture kit (CLiCK) for spheroids, termed CLiCK-Spheroid. This platform consists of three primary components: a hanging drop microarray (HDMA), a concave pillar microarray (CPMA), and gradient blocks. The HDMA alone produces a homogeneous spheroid array, while its combination with the gradient block enables one-step generation of a size-gradient spheroid array. Using the size-gradient spheroid arrays, the occurrence of necrotic cores based on spheroid size is demonstrated. Additionally, spheroids in a single batch can be conveniently compartmentalized and regrouped using a CPMA, enhancing the versatility of spheroid arrays and enabling multiplexed drug treatments. By combining the different assembly methods, this work has achieved high-throughput production of cell composition-gradient spheroid arrays, with noticeable variations in morphology and vascularization based on cell compositions.

Superhydrophobic Array Devices for the Enhanced Formation of 3D Cancer Models

During the metastatic cascade, cancer cells travel through the bloodstream as circulating tumor cells (CTCs) to a secondary site. Clustered CTCs have greater shear stress and treatment resistance, yet their biology remains poorly understood. We therefore engineered a tunable superhydrophobic array device (SHArD). The SHArD-C was applied to culture a clinically relevant model of CTC clusters. Using our device, we cultured a model of cancer cell aggregates of various sizes with immortalized cancer cell lines. These exhibited higher E-cadherin expression and are significantly more capable of surviving high fluid shear stress-related forces compared to single cells and model clusters grown using the control method, helping to explain why clustering may provide a metastatic advantage. Additionally, the SHArD-S, when compared with the AggreWell 800 method, provides a more consistent spheroid-forming device culturing reproducible sizes of spheroids for multiple cancer cell lines. Overall, we designed, fabricated, and validated an easily tunable engineered device which grows physiologically relevant three-dimensional (3D) cancer models containing tens to thousands of cells.

Continuous flow delivery system for the perfusion of scaffold-based 3D cultures

The paper-based culture platform developed by Whitesides readily incorporates tissue-like structures into laboratories with established workflows that rely on monolayer cultures. Cell-laden hydrogels are deposited in these porous scaffolds with micropipettes; these scaffolds support the thin gel slabs, allowing them to be evaluated individually or stacked into thick constructs. The paper-based culture platform has inspired many basic and translational studies, each exploring how readily accessible materials can generate complex structures that mimic aspects of tissues in vivo. Many of these examples have relied on static culture conditions, which result in diffusion-limited environments and cells experiencing pericellular hypoxia. Perfusion-based systems can alleviate pericellular hypoxia and other cell stresses by continually exposing the cells to fresh medium. These perfusion systems are common in microfluidic and organ-on-chip devices supporting cells as monolayer cultures or as 3D constructs. Here, we introduce a continuous flow delivery system, which uses parts readily produced with 3D printing to provide a self-contained culture platform in which cells in paper or other scaffolds are exposed to fresh (flowing) medium. We demonstrate the utility of this device with examples of cells maintained in single cell-laden scaffolds, stacks of cell-laden scaffolds, and scaffolds that contain monolayers of endothelial cells. These demonstrations highlight some possible experimental questions that can be enabled with readily accessible culture materials and a perfusion-based device that can be readily fabricated.

Forming Single-Cell-Derived Colon Cancer Organoid Arrays on a Microfluidic Chip for High Throughput Tumor Heterogeneity Analysis

Single-cell-derived tumor organoids (STOs) possess a distinct genetic background, making them valuable tools for demonstrating tumor heterogeneity. In order to fulfill the high throughput demands of STO assays, we have developed a microfluidic chip containing 30 000 microwells, which is dedicated to a single cell culture approach for selective expansion and differential induction of cancer stem cells. The microwells are coated with a hydrophilic copolymer to eliminate cell adhesion, and the cell culture is supported by poly(ethylene glycol) (PEG) to establish a nonadhesive culture environment. By utilizing an input cell density of 7 × 103·mL-1, it is possible to construct a 4000 single cell culture system through stochastic cell occupation. We demonstrate that the addition of 15% PEG10000 in the cell culture medium effectively prevents cell loss while facilitating tumor stem cell expansion. As were demonstrated by HCT116, HT29, and SW480 colon cancer cells, the microfluidic approach achieved a STO formation rate of ∼20%, resulting in over 800 STOs generated from a single culture. Comprehensive analysis through histomorphology, immunohistochemistry, drug response evaluation, assessment of cell invasion, and biomarker detection reveals the heterogeneity among individual STOs. Specifically, the smaller STOs exhibited higher invasion and drug resistance capabilities compared with the larger ones. The developed microfluidic approach effectively facilitates STO formation and offers promising prospects for investigating tumor heterogeneity, as well as conducting personalized therapy-focused drug screening.

From Chips-in-Lab to Point-of-Care Live Cell Device: Development of a Microfluidic Device for On-Site Cell Culture and High-Throughput Drug Screening

Live cell assays provide real-time data of cellular responses. In combination with microfluidics, applications such as automated and high-throughput drug screening on live cells can be accomplished in small devices. However, their application in point-of-care testing (POCT) is limited by the requirement for bulky equipment to maintain optimal cell culture conditions. In this study, we propose a POCT device that allows on-site cell culture and high-throughput drug screening on live cells. We first observe that cell viabilities are substantially affected by liquid evaporation within the microfluidic device, which is intrinsic to the polydimethylsiloxane (PDMS) material due to its hydrophobic nature and nanopatterned surface. The unwanted PDMS-liquid-air interface in the cell culture environment can be eliminated by maintaining a persistent humidity of 95-100% or submerging the whole microfluidic device under water. Our results demonstrate that in the POCT device equipped with a water tank, both primary cells and cell lines can be maintained for up to 1 week without the need for external cell culture equipment. Moreover, this device is powered by a standard alkali battery and can automatically screen over 5000 combinatorial drug conditions for regulating neural stem cell differentiation. By monitoring dynamic variations in fluorescent markers, we determine the optimal doses of platelet-derived growth factor and epidermal growth factor to suppress proinflammatory S100A9-induced neuronal toxicities. Overall, this study presents an opportunity to transform lab-on-a-chip technology from a laboratory-based approach to actual point-of-care devices capable of performing complex experimental procedures on-site and offers significant advancements in the fields of personalized medicine and rapid clinical diagnostics.

3D printed autoclavable biocompatible biodegradable bioreactor vessels with integrated sparger made from poly-lactic acid

3D printing has become widespread for the manufacture of parts in various industries and enabled radically new designs. This trend has not spread to bioprocess development yet, due to a lack of material suitable for the current workflow, including sterilization by autoclaving. This work demonstrates that commercially available heat temperature stable poly-lactic acid (PLA) can be used to easily manufacture novel bioreactor vessels with included features like harvest tubes and 3D printed spargers. Temperature responsiveness was tested for PLA, temperature stable PLA (PLA-HP) and glass for temperatures relevant for insect and mammalian cell culture, including temperature shifts within the process. Stability at 27 °C and 37 °C as well as temperature shifts to 22 °C and 32 °C showed acceptable performance with slightly higher temperature overshoot for 3D printed vessels. A stable temperature is reached after 2 h for PLA, 3 h for PLA-HP and 1 h for glass reactors. Temperature can be maintained with a fluctuation of 0.1 °C for all materials. A 3D printed sparger design directly integrated into the vessel wall and bottom was tested under three different conditions (0.3 SLPH and 27 °C, 3 SLPH and 37 °C and 13 SLPH and 37 °C). The 3D printed sparger showed a better kLa than the L-Sparger with more pronounced differences for higher flowrates. An insect cell culture run in the novel vessel exhibited the same growth behavior as that in standard glass vessels, reaching the same maximum cell concentration. Being 3D printed from biodegradable materials, these bioreactors offer design flexibility for novel bioreactor formats. Additionally, their autoclavability allows seamless integration into standard workflows.

DirectedCHO: A new miniaturized directed evolution process for phenotype stability trial test of CHO cells before bioreactor scale-up

Most of the biopharmaceuticals that are currently on the market are expressed using the Chinese Hamster Ovary (CHO) cell lines. However, the production yield of these biopharmaceuticals is affected due to CHO cellular heterogeneity and challenges in adaptability during the bioreactor scale-up stage. In this communication, we report the protocol for the miniaturized directed evolution process for CHO cells. The results of the directed evolution process would guide adapting the CHO cell line before bioreactor scale-up. With our approach, we have established the protocol that can be used to streamline superior CHO cell lines for biopharmaceutical production which would be the first of its kind in Africa. Our directed evolution protocol includes a method for a low-cost multiplex directed evolution process that can be used on CHO cells using 20 stressors in 8 concentrations and provides stable trial results for the scale-up process. Using our process, we can provide a simple consumable kit that manufacturers can use for the CHO cell phenotype stability test before the scale-up process. With our approach, we would further develop a platform that can streamline superior CHO cell lines for biopharmaceutical production. This approach would be the first of its kind in South Africa/ Africa.

Innovative fixed bed bioreactor platform: Enabling linearly scalable adherent cell biomanufacturing with real-time biomass prediction from nutrient consumption

Scalable single-use adherent cell-based biomanufacturing platforms are essential for unlocking the full potential of cell and gene therapies. The primary objective of this study is to design and develop a novel fixed bed bioreactor platform tailored specifically for scaling up adherent cell culture. The bioreactor comprises a packed bed of vertically stacked woven polyethylene terephthalate mesh discs, sandwiched between two-fluid guide plates. Leveraging computational fluid dynamics modeling, we optimized bioreactor design to achieve uniform flow with minimal shear stress. Residence time distribution measurements demonstrated excellent flow uniformity with plug flow characteristics. Periodic media sampling coupled with offline analysis revealed minimal gradients of crucial metabolites (glucose, glutamine, lactate, and ammonia) across the bioreactor during cell growth. Furthermore, the bioreactor platform demonstrated high performance in automated cell harvesting, with ≈96% efficiency and ≈98% viability. It also exhibited linear scalability in both operational parameters and performance for cell culture and adeno-associated virus vector production. We developed mathematical models based on oxygen uptake rates to accurately predict cell growth curves and estimate biomass in real-time. This study demonstrates the effectiveness of the developed fixed-bed bioreactor platform in enabling scalable adherent cell-based biomanufacturing with high productivity and process control.

Electrical Capacitance Tomography of Cell Cultures on a CMOS Microelectrode Array

Electrical capacitance tomography (ECT) can be used to predict information about the interior volume of an object based on measured capacitance at its boundaries. Here, we present a microscale capacitance tomography system with a spatial resolution of 10 microns using an active CMOS microelectrode array. We introduce a deep learning model for reconstructing 3-D volumes of cell cultures using the boundary capacitance measurements acquired from the sensor array, which is trained using a multi-objective loss function that combines a pixel-wise loss function, a distribution-based loss function, and a region-based loss function to improve model's reconstruction accuracy. The multi-objective loss function enhances the model's reconstruction accuracy by 3.2% compared to training only with a pixel-wise loss function. Compared to baseline computational methods, our model achieves an average of 4.6% improvement on the datasets evaluated. We demonstrate our approach on experimental datasets of bacterial biofilms, showcasing the system's ability to resolve microscopic spatial features of cell cultures in three dimensions. Microscale capacitance tomography can be a low-cost, low-power, label-free tool for 3-D imaging of biological samples.

Single-Use, Metabolite Absorbing, Resonant Transducer (SMART) Culture Vessels for Label-Free, Continuous Cell Culture Progression Monitoring

Secreted metabolites are an important class of bio-process analytical technology (PAT) targets that can correlate to cell conditions. However, current strategies for measuring metabolites are limited to discrete measurements, resulting in limited understanding and ability for feedback control strategies. Herein, a continuous metabolite monitoring strategy is demonstrated using a single-use metabolite absorbing resonant transducer (SMART) to correlate with cell growth. Polyacrylate is shown to absorb secreted metabolites from living cells containing hydroxyl and alkenyl groups such as terpenoids, that act as a plasticizer. Upon softening, the polyacrylate irreversibly conformed into engineered voids above a resonant sensor, changing the local permittivity which is interrogated, contact-free, with a vector network analyzer. Compared to sensing using the intrinsic permittivity of cells, the SMART approach yields a 20-fold improvement in sensitivity. Tracking growth of many cell types such as Chinese hamster ovary, HEK293, K562, HeLa, and E. coli cells as well as perturbations in cell proliferation during drug screening assays are demonstrated. The sensor is benchmarked to show continuous measurement over six days, ability to track different growth conditions, selectivity to transducing active cell growth metabolites against other components found in the media, and feasibility to scale out for high throughput campaigns.

High-Throughput 3D Imaging Flow Cytometry of Suspended Adherent 3D Cell Cultures

3D cell cultures are indispensable in recapitulating in vivo environments. Among the many 3D culture methods, culturing adherent cells on hydrogel beads to form spheroid-like structures is a powerful strategy for maintaining high cell viability and functions in the adherent states. However, high-throughput, scalable technologies for 3D imaging of individual cells cultured on the hydrogel scaffolds are lacking. This study reports the development of a high throughput, scalable 3D imaging flow cytometry platform for analyzing spheroid models. This platform is realized by integrating a single objective fluorescence light-sheet microscopy with a microfluidic device that combines hydrodynamic and acoustofluidic focusing techniques. This integration enabled unprecedentedly high-throughput and scalable optofluidic 3D imaging, processing 1310 spheroids consisting of 28 117 cells min-1. The large dataset obtained enables precise quantification and comparison of the nuclear morphology of adhering and suspended cells, revealing that the adhering cells have smaller nuclei with less rounded surfaces. This platform's high throughput, robustness, and precision for analyzing the morphology of subcellular structures in 3D culture models hold promising potential for various biomedical analyses, including image-based phenotypic screening of drugs with spheroids or organoids.

A closed 3D printed microfluidic device for automated growth and differentiation of cerebral organoids from single-cell suspension

The development of 3D organoids has provided a valuable tool for studying human tissue and organ development in vitro. Cerebral organoids, in particular, offer a unique platform for investigating neural diseases. However, current methods for generating cerebral organoids suffer from limitations such as labor-intensive protocols and high heterogeneity among organoids. To address these challenges, we present a microfluidic device designed to automate and streamline the formation and differentiation of cerebral organoids. The device utilizes microwells with two different shapes to promote the formation of a single aggregate per well and incorporates continuous medium flow for optimal nutrient exchange. In silico simulations supported the effectiveness of the microfluidic chip in replicating cellular microenvironments. Our results demonstrate that the microfluidic chip enables uniform growth of cerebral organoids, significantly reducing the hands-on time required for maintenance. Importantly, the performance of the microfluidic system is comparable to the standard 96-well plate format even when using half the amount of culture medium, and the resulting organoids exhibit substantially developed neuroepithelial buds and cortical structures. This study highlights the potential of custom-designed microfluidic technology in improving the efficiency of cerebral organoid culture.

Fabrication of heterocellular spheroids with controllable core-shell structure using inertial focusing effect for scaffold-free 3D cell culture models

Three-dimensional (3D) cell culture models capable of emulating the biological functions of natural tissues are pivotal in tissue engineering and regenerative medicine. Despite progress, the fabrication ofin vitroheterocellular models that mimic the intricate structures of natural tissues remains a significant challenge. In this study, we introduce a novel, scaffold-free approach leveraging the inertial focusing effect in rotating hanging droplets for the reliable production of heterocellular spheroids with controllable core-shell structures. Our method offers precise control over the core-shell spheroid's size and geometry by adjusting the cell suspension density and droplet morphology. We successfully applied this technique to create hair follicle organoids, integrating dermal papilla cells within the core and epidermal cells in the shell, thereby achieving markedly enhanced hair inducibility compared to mixed-structure models. Furthermore, we have developed melanoma tumor spheroids that accurately mimic the dynamic interactions between tumor and stromal cells, showing increased invasion capabilities and altered expressions of cellular adhesion molecules and proteolytic enzymes. These findings underscore the critical role of cellular spatial organization in replicating tissue functionalityin vitro. Our method represents a significant advancement towards generating heterocellular spheroids with well-defined architectures, offering broad implications for biological research and applications in tissue engineering.

Developing Device of Death Operation (DODO) to Detect Apoptosis in 2D and 3D Cultures

The real-time detection of intracellular biological processes by encoded sensors has broad application prospects. Here, we developed a degron-based modular reporting system, the Device of Death Operation (DODO), that can monitor various biological processes. The DODO system consists of a "reporter", an "inductor", and a "degron". After zymogen activation and cleavage, the degron will be released from the "reporter", which eventually leads to the stabilization of the "reporter", and can be detected. By replacing different "inductors" and "reporters", a series of biological processes can be reported through various signals. The system can effectively report the existence of TEV protease. To prove this concept, we successfully applied the DODO system to report apoptosis in 2D and 3D cultures. In addition, the reporter based on degron will help to design protease reporters other than caspase.

Reversibly-bonded microfluidic devices for stable cell culture and rapid, gentle cell extraction

Microfluidic chips have emerged as significant tools in cell culture due to their capacity for supporting cells to adopt more physiologically relevant morphologies in 3D compared with traditional cell culture in 2D. Currently, irreversible bonding methods, where chips cannot be detached from their substrates without destroying the structure, are commonly used in fabrication, making it challenging to conduct further analysis on cells that have been cultured on-chip. Although some reversible bonding techniques have been developed, they are either restricted to certain materials such as glass, or require complex processing procedures. Here, we demonstrate a simple and reversible polydimethylsiloxane (PDMS)-polystyrene (PS) bonding technique that allows devices to withstand extended operations while pressurized, and supports long-term stable cell cultures. More importantly, it allows rapid and gentle live cell extraction for downstream manipulation and characterization after long-term on-chip culturing, and even further subculturing. Our new approach could greatly facilitate microfluidic chip-based cell and tissue cultures, overcoming current analytical limitations and opening up new avenues for downstream uses of on-chip cultures, including 3D-engineered tissue structures for biomedical applications.

Cell-based shear stress sensor for bioprocessing

Shear stress during bioreactor cultivation has significant impact on cell health, growth, and fate. Mammalian cells, such as T cells and stem cells, in next-generation cell therapies are especially more sensitive to shear stress present in their culture environment than bacteria. Therefore, a base knowledge about the shear stress imposed by the bioprocesses is needed to optimize the process parameters and enhance cell growth and yield. However, typical computational flow dynamics modeling or PCR-based assays have several limitations. Implementing and interpreting computational modeling often requires technical specialties and also relies on many simplifications in modeling. PCR-based assays evaluating changes in gene expression involve cumbersome sample preparation with the use of advanced lab equipment and technicians, hampering rapid and straightforward assessment of shear stress. Here, we developed a simple, cell-based shear stress sensor for measuring shear stress levels in different bioreactor types and operating conditions. We engineered a CHO-DG44 cell line to make its stress sensitive promoter EGR-1 control GFP expression. Subsequently, the stressed CHO cells were transferred into a 96 well plate, and their GFP levels (population mean fluorescence) were monitored using a cell analysis instrument (Incucyte®, Sartorius Stedim Biotech) over 24 hours. After conducting sensor characterization, which included chemical induced stress and fluid shear stress, and stability investigation, we tested the shear stress sensor in the Ambr® 250 bioreactor vessels (Sartorius Stedim Biotech) with different impeller and vessel designs. The results showed that the CHO cell-based shear stress sensors expressed higher GFP levels in response to higher shear stress magnitude or exposure time. These sensors are useful tools to assess shear stress imposed by bioreactor conditions and can facilitate the design of various bioreactor vessels with a low shear stress profile.

Mapping the microcarrier design pathway to modernise clinical mesenchymal stromal cell expansion

Microcarrier expansion systems show exciting potential to revolutionise mesenchymal stromal cell (MSC)-based clinical therapies by providing an opportunity for economical large-scale expansion of donor- and patient-derived cells. The poor reproducibility and efficiency of cell expansion on commercial polystyrene microcarriers have driven the development of novel microcarriers with tuneable physical, mechanical, and cell-instructive properties. These new microcarriers show innovation toward improving cell expansion outcomes, although their limited biological characterisation and compatibility with dynamic culture systems suggest the need to realign the microcarrier design pathway. Clear headway has been made toward developing infrastructure necessary for scaling up these technologies; however, key challenges remain in characterising the wholistic effects of microcarrier properties on the biological fate and function of expanded MSCs.

Precision Culture Scaling to Establish High-Throughput Vasculogenesis Models

Hydrogel-based 3D cell cultures can recapitulate (patho)physiological phenomena ex vivo. However, due to their complex multifactorial regulation, adapting these tissue and disease models for high-throughput screening workflows remains challenging. In this study, a new precision culture scaling (PCS-X) methodology combines statistical techniques (design of experiment and multiple linear regression) with automated, parallelized experiments and analyses to customize hydrogel-based vasculogenesis cultures using human umbilical vein endothelial cells and retinal microvascular endothelial cells. Variations of cell density, growth factor supplementation, and media composition are systematically explored to induce vasculogenesis in endothelial mono- and cocultures with mesenchymal stromal cells or retinal microvascular pericytes in 384-well plate formats. The developed cultures are shown to respond to vasculogenesis inhibitors in a compound- and dose-dependent manner, demonstrating the scope and power of PCS-X in creating parallelized tissue and disease models for drug discovery and individualized therapies.

Phase-amplitude coupling detection and analysis of human 2-dimensional neural cultures in multi-well microelectrode array in vitro

BACKGROUND

Human induced pluripotent stem cell (hiPSC)- derived neurons offer the possibility of studying human-specific neuronal behaviors in physiologic and pathologic states in vitro. It is unclear whether cultured neurons can achieve the fundamental network behaviors required to process information in the brain. Investigating neuronal oscillations and their interactions, as occurs in cross-frequency coupling (CFC), addresses this question.

NEW METHODS

We examined whether networks of two-dimensional (2D) cultured hiPSC-derived cortical neurons grown with hiPSC-derived astrocytes on microelectrode array plates recapitulate the CFC that is present in vivo. We employed the modulation index method for detecting phase-amplitude coupling (PAC) and used offline spike sorting to analyze the contribution of single neuron spiking to network behavior.

RESULTS

We found that PAC is present, the degree of PAC is specific to network structure, and it is modulated by external stimulation with bicuculline administration. Modulation of PAC is not driven by single neurons, but by network-level interactions.

COMPARISON WITH EXISTING METHODS

PAC has been demonstrated in multiple regions of the human cortex as well as in organoids. This is the first report of analysis demonstrating the presence of coupling in 2D cultures.

CONCLUSION

CFC in the form of PAC analysis explores communication and integration between groups of neurons and dynamical changes across networks. In vitro PAC analysis has the potential to elucidate the underlying mechanisms as well as capture the effects of chemical, electrical, or ultrasound stimulation; providing insight into modulation of neural networks to treat nervous system disorders in vivo.