Microfluidic Cell Culture System Research Articles

Evaluation of transfection with gemini nanoparticles for retinal neuroprotection in a dynamic microfluidic cell culture system

<img src=” https://s3.amazonaws.com/production.scholastica/article/94464/large/prnano_1252024ga.jpg?1709170827”> Glaucoma is a neurodegenerative disease of the retina and optic nerve with elevated intraocular pressure as one of the main contributing factors. The traditional in vitro methods to evaluate new gene delivery systems for neuroprotective treatments of glaucoma require testing in cell monolayers under static conditions. Therefore, a microfluidic technology that provides a dynamic simulation of cell exposure to nanoparticles (NPs) could be a useful model for rapid screening. In this study, CellASIC ONIX2 microfluidic platform was used to evaluate and optimize culture and transfection conditions to assess cell viability and transfection efficiency (TE) of gemini NPs carrying GFP-encoding plasmid in A7 astrocytes, one of the targeted retinal cells for glaucoma treatment. The average TE (inlet-middle-outlet of culture chambers) by gemini nanoplexes, 18-7NH-18 NPXs and 18-7Np3-18 NPXs was > 85% and > 25%, respectively, after 5 h of perfusion with a combined average FI (caFI) of about 600 and < 100, respectively, whereas TE after Lipofectamine 3000 was > 70% and caFI of < 100. The results have shown that comparatively to 2D monolayers, the microfluidics technique provides better exposure of cells to NPs, suitable for kinetic mapping of gene expression, and a useful tool for cell growth and live evaluation of gene delivery system interaction with cells.

Advances in high throughput cell culture technologies for therapeutic screening and biological discovery applications

AbstractCellular phenotypes and functional responses are modulated by the signals present in their microenvironment, including extracellular matrix (ECM) proteins, tissue mechanical properties, soluble signals and nutrients, and cell–cell interactions. To better recapitulate and analyze these complex signals within the framework of more physiologically relevant culture models, high throughput culture platforms can be transformative. High throughput methodologies enable scientists to extract increasingly robust and broad datasets from individual experiments, screen large numbers of conditions for potential hits, better qualify and predict responses for preclinical applications, and reduce reliance on animal studies. High throughput cell culture systems require uniformity, assay miniaturization, specific target identification, and process simplification. In this review, we detail the various techniques that researchers have used to face these challenges and explore cellular responses in a high throughput manner. We highlight several common approaches including two‐dimensional multiwell microplates, microarrays, and microfluidic cell culture systems as well as unencapsulated and encapsulated three‐dimensional high throughput cell culture systems, featuring multiwell microplates, micromolds, microwells, microarrays, granular hydrogels, and cell‐encapsulated microgels. We also discuss current applications of these high throughput technologies, namely stem cell sourcing, drug discovery and predictive toxicology, and personalized medicine, along with emerging opportunities and future impact areas.

Simultaneous Separating, Splitting, Collecting, and Dispensing by Droplet Pinch-Off for Droplet Cell Culture.

Simultaneous separating, splitting, collecting, and dispensing a cell suspension droplet has been demonstrated by aspiration and subsequent droplet pinch-off for use in microfluidic droplet cell culture systems. This method is applied to cell manipulations including aliquots and concentrations of microalgal and mammalian cell suspensions. Especially, medium exchange of spheroid droplets is successfully demonstrated by collecting more than 99% of all culture medium without damaging the spheroids, demonstrating its potential for a 3D cell culture system. Through dimensional analysis and systematic parametric studies, it is found that initial mother droplet size together with aspiration flow rate determines three droplet pinch-off regimes. By observing contact angle changes during aspiration, the difference in the large and the small droplet pinch-off can be quantitatively explained using force balance. It is found that the capillary number plays a significant role in droplet pinch-off, but the Bond number and the Ohnesorge number have minor effects. Since the dispensed droplet size is mainly determined by the capillary number, the dispensed droplet size can be controlled simply by adjusting the aspiration flow rate. It is hoped that this method can contribute to various fields using droplets, such as droplet cell culture and digital microfluidics, beyond the generation of small droplets.

Optical glucose sensor for microfluidic cell culture systems

Glucose is the primary energy source of human cells. Therefore, monitoring glucose inside microphysiological systems (MPS) provides valuable information on the viability and metabolic state of the cultured cells. However, continuous glucose monitoring inside MPS is challenging due to a lack of suitable miniaturized sensors. Here we present an enzymatic, optical glucose sensor element for measurement inside microfluidic systems. The miniaturized glucose sensor (Ø 1 mm) is fabricated together with a reference oxygen sensor onto biocompatible, pressure-sensitive adhesive tape for easy integration inside microfluidic systems. Furthermore, the proposed microfluidic system can be used as plug and play sensor system with existing MPS. It was characterized under cell culture conditions (37 °C and pH 7.4) for five days, exhibiting minor drift (3% day−1). The influence of further cell culture parameters like oxygen concentration, pH, flow rate, and sterilization methods was investigated. The plug-and-play system was used for at-line measurements of glucose levels in (static) cell culture and achieved good agreement with a commercially available glucose sensor. In conclusion, we developed an optical glucose sensor element that can be easily integrated in microfluidic systems and is able to perform stable glucose measurements under cell culture conditions.

Development of a novel microfluidic perfusion 3D cell culture system for improved neuronal cell differentiation.

Three-dimensional (3D) cell cultures have recently gained popularity in the biomedical sciences because of their similarity to the in vivo environment. SH-SY5Y cells, which are neuronal cells and are commonly used to investigate neurodegenerative diseases, have particularly been reported to be differentiated as neuron-like cells expressing neuron-specific markers of mature neurons in static 3D culture environments when compared to static 2D environments, and those in perfusion environments have not yet been investigated. Microfluidic technology has provided perfusion environment which has more similarity to in vivo through mimicking vascular transportation of nutrients, but air bubbles entering into microchannels drastically increase instability of the flow. Furthermore, static incubation commonly used is incompatible with perfusion setup due to its air conditions, which is a critical huddle to the biologists. In the present study, we developed a novel microfluidic perfusion 3D cell culture system that overcomes the disturbance from air bubbles and intuitionally sets the incubation with the perfusion 3D culture. The system is capable of generating concentration gradients between 5 and 95% and air bubble traps were included to increase stability during incubation by collecting air bubbles. To evaluate the perfusion 3D culture, SH-SY5Y differentiation was examined in static 2D, static 3D, and perfusion 3D cultures. Our system supported significantly increased clustering of SH-SY5Y compared to static 2D and 3D methods, as well as increasing neurite growth rate. This novel system therefore supports differentiation of SH-SY5Y and can be used to more accurately model the in vivo environment during cell culture experiments.

Development of a Redox-Polymer-Based Electrochemical Glucose Biosensor Suitable for Integration in Microfluidic 3D Cell Culture Systems.

The inclusion of online, in situ biosensors in microfluidic cell cultures is important to monitor and characterize a physiologically mimicking environment. This work presents the performance of second-generation electrochemical enzymatic biosensors to detect glucose in cell culture media. Glutaraldehyde and ethylene glycol diglycidyl ether (EGDGE) were tested as cross-linkers to immobilize glucose oxidase and an osmium-modified redox polymer on the surface of carbon electrodes. Tests employing screen printed electrodes showed adequate performance in a Roswell Park Memorial Institute (RPMI-1640) media spiked with fetal bovine serum (FBS). Comparable first-generation sensors were shown to be heavily affected by complex biological media. This difference is explained in terms of the respective charge transfer mechanisms. Under the tested conditions, electron hopping between Os redox centers was less vulnerable than H2O2 diffusion to biofouling by the substances present in the cell culture matrix. By employing pencil leads as electrodes, the incorporation of these electrodes in a polydimethylsiloxane (PDMS) microfluidic channel was achieved simply and at a low cost. Under flow conditions, electrodes fabricated using EGDGE presented the best performance with a limit of detection of 0.5 mM, a linear range up to 10 mM, and a sensitivity of 4.69 μA mM-1 cm-2.

Hydrogel-based microfluidic device with multiplexed 3D in vitro cell culture

Microfluidic devices that combine an extracellular matrix environment, cells, and physiologically relevant perfusion, are advantageous as cell culture platforms. We developed a hydrogel-based, microfluidic cell culture platform by loading polyethylene glycol (PEG) hydrogel-encapsulated U87 glioblastoma cells into membrane-capped wells in polydimethyl siloxane (PDMS). The multilayer microfluidic cell culture system combines previously reported design features in a configuration that loads and biomimetically perfuses a 2D array of cell culture chambers. One dimension of the array is fed by a microfluidic concentration gradient generator (MCGG) while the orthogonal dimension provides loading channels that fill rows of cell culture chambers in a separate layer. In contrast to typical tree-like MCGG mixers, a fractional serial dilution of 1, ½, ¼, and 0 of the initial solute concentration is achieved by tailoring the input microchannel widths. Hydrogels are efficiently and reproducibly loaded in all wells and cells are evenly distributed throughout the hydrogel, maintaining > 90% viability for up to 4 days. In a drug screening assay, diffusion of temozolomide and carmustine to hydrogel-encapsulated U87 cells from the perfusion solution is measured, and dose–response curves are generated, demonstrating utility as an in vitro mimic of the glioblastoma microenvironment.

A human model of arteriovenous malformation (AVM)-on-a-chip reproduces key disease hallmarks and enables drug testing in perfused human vessel networks

Brain arteriovenous malformations (AVMs) are a disorder wherein abnormal, enlarged blood vessels connect arteries directly to veins, without an intervening capillary bed. AVMs are one of the leading causes of hemorrhagic stroke in children and young adults. Most human sporadic brain AVMs are associated with genetic activating mutations in the KRAS gene. Our goal was to develop an in vitro model that would allow for simultaneous morphological and functional phenotypic data capture in real time during AVM disease progression. By generating human endothelial cells harboring a clinically relevant mutation found in most human patients (activating mutations within the small GTPase KRAS) and seeding them in a dynamic microfluidic cell culture system that enables vessel formation and perfusion, we demonstrate that vessels formed by KRAS4AG12V mutant endothelial cells (ECs) were significantly wider and more leaky than vascular beds formed by wild-type ECs, recapitulating key structural and functional hallmarks of human AVM pathogenesis. Immunofluorescence staining revealed a breakdown of adherens junctions in mutant KRAS vessels, leading to increased vascular permeability, a hallmark of hemorrhagic stroke. Finally, pharmacological blockade of MEK kinase activity, but not PI3K inhibition, improved endothelial barrier function (decreased permeability) without affecting vessel diameter. Collectively, our studies describe the creation of human KRAS-dependent AVM-like vessels in vitro in a self-assembling microvessel platform that is amenable to phenotypic observation and drug delivery.

Radiobiological effects of wound fluid on breast cancer cell lines and human-derived tumor spheroids in 2D and microfluidic culture

Intraoperative radiotherapy (IORT) could abrogate cancer recurrences, but the underlying mechanisms are unclear. To clarify the effects of IORT-induced wound fluid on tumor progression, we treated breast cancer cell lines and human-derived tumor spheroids in 2D and microfluidic cell culture systems, respectively. The viability, migration, and invasion of the cells under treatment of IORT-induced wound fluid (WF-RT) and the cells under surgery-induced wound fluid (WF) were compared. Our findings showed that cell viability was increased in spheroids under both WF treatments, whereas viability of the cell lines depended on the type of cells and incubation times. Both WFs significantly increased sub-G1 and arrested the cells in G0/G1 phases associated with increased P16 and P21 expression levels. The expression level of Caspase 3 in both cell culture systems and for both WF-treated groups was significantly increased. Furthermore, our results revealed that although the migration was increased in both systems of WF-treated cells compared to cell culture media-treated cells, E-cadherin expression was significantly increased only in the WF-RT group. In conclusion, WF-RT could not effectively inhibit tumor progression in an ex vivo tumor-on-chip model. Moreover, our data suggest that a microfluidic system could be a suitable 3D system to mimic in vivo tumor conditions than 2D cell culture.

The effect of shear stress on cardiac differentiation of mesenchymal stem cells.

Stem cell therapy is developing as a valuable therapeutic trend for heart diseases. Most recent studies are aimed to find the most appropriate types of stem cells for the treatment of myocardial infarction (MI). The animal models have shown that bone marrow-derived mesenchymal stem cells (BMSCs) are a possible, safe, and efficient type of stem cell used in MI. The previous study demonstrated that 5-Azacytidine (5-Aza) could promote cardiac differentiation in stem cells. This study used 5-Aza to induce cardiomyocyte differentiation in BMSCs both in static and microfluidic cell culture systems. For this purpose, we investigated the differentiation by using real-time PCR and Immunocytochemistry (ICC) Analysis. Our results showed that 5-Aza could cause to express cardiac markers in BMSCs as indicated by real-time PCR and immunocytochemistry (ICC). However, BMSCs are exposed to both 5-Aza and shear stress, and their synergistic effects could significantly induce cardiac gene expressions in BMSCs. This level of gene expression was observed neither in 5-Aza nor in shear stress groups only. These results demonstrate that when BMSCs expose to 5-Aza as well as mechanical cues such as shear stress, the cardiac gene expression can be increased dramatically.

Development of a microfluidic cell culture system for the adaptive laboratory evolution

We construct a microfluidics-based long-term cell culture system that can perform multiple adaptive laboratory evolution (ALE) experiments in parallel under different conditions. Single E. coli cells were isolated into water droplets in oil (W/O emulsion) containing agarose gel. Micrometric gel balls (GBs) were then extracted from the oil phase and placed in a microfluidic perfusion culture device, which can generate a substrate concentration gradient. The growth of the clonal colonies was monitored under each condition. We tested this GB-based culture device to expand the application of ALE after the gene knockout based on the flux balance analysis (FBA) performed in our previous studies.

Angiogenic Sprouting Dynamics Mediated by Endothelial‐Fibroblast Interactions in Microfluidic Systems (Adv. Biology 11/2021)

Angiogenic Sprouting Dynamics In article 2101080, Young and co-workers examinate the angiogenic sprouts (orange) extend from a 3D endothelial lumen on the left towards a fibroblast spheroid (blue) on the right, all in a microfluidic cell culture system. Triangular microposts (dark triangles) separate the central microchannel containing the fibroblast spheroid from the left microchannel containing the endothelial lumen. The sprouts are observed to surround the spheroid.

Recent advances of integrated microfluidic suspension cell culture system.

Microfluidic devices with superior microscale fluid manipulation ability and large integration flexibility offer great advantages of high throughput, parallelisation and multifunctional automation. Such features have been extensively utilised to facilitate cell culture processes such as cell capturing and culturing under controllable and monitored conditions for cell-based assays. Incorporating functional components and microfabricated configurations offered different levels of fluid control and cell manipulation strategies to meet diverse culture demands. This review will discuss the advances of single-phase flow and droplet-based integrated microfluidic suspension cell culture systems and their applications for accelerated bioprocess development, high-throughput cell selection, drug screening and scientific research to insight cell biology. Challenges and future prospects for this dynamically developing field are also highlighted.

Three-dimensional microengineered vascularised endometrium-on-a-chip.

STUDY QUESTIONCan we reconstitute physiologically relevant 3-dimensional (3D) microengineered endometrium in-vitro model?SUMMARY ANSWEROur representative microengineered vascularised endometrium on-a-chip closely recapitulates the endometrial microenvironment that consists of three distinct layers including epithelial cells, stromal fibroblasts and endothelial cells in a 3D extracellular matrix in a spatiotemporal manner.WHAT IS KNOWN ALREADYOrgan-on-a-chip, a multi-channel 3D microfluidic cell culture system, is widely used to investigate physiologically relevant responses of organ systems.STUDY DESIGN, SIZE, DURATIONThe device consists of five microchannels that are arrayed in parallel and partitioned by array of micropost. Two central channels are for 3D culture and morphogenesis of stromal fibroblast and endothelial cells. In addition, the outermost channel is for the culture of additional endometrial stromal fibroblasts that secrete biochemical cues to induce directional pro-angiogenic responses of endothelial cells. To seed endometrial epithelial cells, on Day 8, Ishikawa cells were introduced to one of the two medium channels to adhere on the gel surface. After that, the microengineered endometrium was cultured for an additional 5–6 days (total ∼ 14 days) for the purpose of each experiment.PARTICIPANTS/MATERIALS, SETTING, METHODSMicrofluidic 3D cultures were maintained in endothelial growth Medium 2 with or without oestradiol and progesterone. Some cultures additionally received exogenous pro-angiogenic factors. For the three distinct layers of microengineered endometrium-on-a-chip, the epithelium, stroma and blood vessel characteristics and drug response of each distinct layer in the microfluidic model were assessed morphologically and biochemically. The quantitative measurement of endometrial drug delivery was evaluated by the permeability coefficients.MAIN RESULTS AND THE ROLE OF CHANCEWe established microengineered vascularised endometrium-on-chip, which consists of three distinct layers: epithelium, stroma and blood vessels. Our endometrium model faithfully recapitulates in-vivo endometrial vasculo-angiogenesis and hormonal responses displaying key features of the proliferative and secretory phases of the menstrual cycle. Furthermore, the effect of the emergency contraception drug levonorgestrel was evaluated in our model demonstrating increased endometrial permeability and blood vessel regression in a dose-dependent manner. We finally provided a proof of concept of the multi-layered endometrium model for embryo implantation, which aids a better understanding of the molecular and cellular mechanisms underlying this process.LARGE SCALE DATAN/A.LIMITATIONS, REASONS FOR CAUTIONThis report is largely an in-vitro study and it would be beneficial to validate our findings using human primary endometrial cells.WIDER IMPLICATIONS OF THE FINDINGSOur 3D microengineered vascularised endometrium-on-a-chip provides a new in-vitro approach to drug screening and drug discovery by mimicking the complicated behaviours of human endometrium. Thus, we suggest our model as a tool for addressing critical challenges and unsolved problems in female diseases, such as endometriosis, uterine cancer and female infertility, in a personalised manner.STUDY FUNDING/COMPETING INTEREST(S)This work is supported by funding from the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) to Y.J.K. (No. 2018R1C1B6003), to J.A. (No. 2020R1I1A1A01074136) and to H.S.K. (No. 2020R1C1C100787212). The authors report no conflicts of interest.

Electric-Field-Induced Neural Precursor Cell Differentiation in Microfluidic Devices.

Physiological electric fields (EF) play vital roles in cell migration, differentiation, division, and death. This paper describes a microfluidic cell culture system that was used for a long-term cell differentiation study using microscopy. The microfluidic system consists of the following major components: an optically transparent electrotactic chip, a transparent indium-tin-oxide (ITO) heater, a culture media-filling pump, an electrical power supply, a high-frequency power amplifier, an EF multiplexer, a programmable X-Y-Z motorized stage, and an inverted phase-contrast microscope equipped with a digital camera. The microfluidic system is beneficial in simplifying the overall experimental setup and, in turn, the reagent and sample consumption. This work involves the differentiation of neural stem and progenitor cells (NPCs) induced by direct current (DC) pulse stimulation. In the stem cell maintenance medium, the mouse NPCs (mNPCs) differentiated into neurons, astrocytes, and oligodendrocytes after the DC pulse stimulation. The results suggest that simple DC pulse treatment could control the fate of mNPCs and could be used to develop therapeutic strategies for nervous system disorders. The system can be used for cell culture in multiple channels, for long-term EF stimulation, for cell morphological observation, and for automatic time-lapse image acquisition. This microfluidic system not only shortens the required experimental time, but also increases the accuracy of control on the microenvironment.

Fabrication of Microfluidic Cell Culture Platform for Real-time Monitoring of Lidocaine Concentration

We describe a microfluidic cell culture platform for real-time measurement of drug concentrations during cell cultivation. This is the first attempt to quantify drug concentrations during cell cultivation in real-time combining ultraviolet–visible (UV–Vis) spectroscopy with a microfluidic cell culture system in a single microfluidic chip. The microfluidic chip has two specific micro-chambers, one for spectroscopic measurements and the other for cell culture. NIH/3T3 fibroblast cells were seeded and cultured in the microfluidic chip, and then the local anesthetic lidocaine was applied and its concentration was monitored in real time. The test results showed that lidocaine negatively affected the cell growth. The lidocaine concentration was decreased due to its intake by cells for the first 3 h, after which an equilibrium concentration was reached. This is a simple but innovative method that can observe and analyze the correlation between cells and drugs in real time. The microfluidic system presented here can be a useful tool in various fields such as in cytotoxicity and drug screening studies.

Single-cell analysis of autoreactive B cells in patients with systemic sclerosis revealed that responses to therapy are determined by effector and regulatory B cell balance

Abstract Objective Systemic sclerosis (SSc) is a connective tissue disease with poor prognosis. Although the standard treatment for skin and lung fibrosis is cyclophosphamide (CYC), there are not a few non-responders to the treatment. Recent studies showed that autoreactive B cells play a critical role in SSc. We hypothesized that these B cells determine the effectiveness of CYC treatment. We focused on cytokine profiles of single autoreactive B cells in patients with SSc. Methods We simulated the interaction of B cells and endothelial cells in microfluidic cell culture systems. We cultured endothelial cells in a microchannel. Then, we loaded B cells of patients with SSc. We collected single B cells which adhere to endothelial cells by trypsin treatment. We stimulated these B cells, with PMA and ionomycin, and measured the levels of produced interleukin (IL)-10 and IL-6 to detect the percentages of regulatory and effector B cells, by our original micro fluidic-ELISA system. Results In SSc patients, the number of B cells adhering to endothelial cells significantly increased compared with healthy controls. Most of these B cells produced anti-endothelial cells antibodies. The frequencies of IL-10-producing regulatory B cells after the CYC treatment increased in responders and decresed in non-responders. Those of IL-6-producing effector B cells after the treatment decreased in responders and increased in non-responders. Conclusions The effectiveness of CYC treatment to SSc patients is associated with cytokine profiles of B cells, which interact with endothelial cells. Checking the profiles of these B cells, after the first few months on from initiation of CYC therapy, may help to decide whether or not we should continue the treatment.

Hydrogels as artificial matrices for cell seeding in microfluidic devices.

Hydrogel-based artificial scaffolds play a vital role in shifting in vitro models from two-dimensional (2D) cell culture to three-dimensional (3D) cell culture. Microfluidic 3D cell culture systems with a hydrogel matrix encourage biomedical researchers to replace in vivo models with 3D in vitro models with a cellular microenvironment that resembles physiological conditions with greater fidelity. Hydrogels can be designed as an artificial extracellular matrix scaffold for providing spatial orientation and promoting cellular interactions with surroundings. Selecting the appropriate hydrogels and their fabrication techniques are the key to mimic the in vivo mechanical environment. Moreover, combining a microfluidic technique with a hydrogel-based 3D cell culture system can create a complex and controlled microenvironment for the cells by placing small biosamples inside the microchannel. This paper provides an overview of the structural similarities of the hydrogels as an extracellular matrix (ECM), their classification and fabrication techniques as an ECM, and their use in microfluidic 3D cell culture systems. Finally, the paper presents the current challenges and future perspectives of using hydrogel scaffolds in microfluidic 3D cell culture systems.

Development of microfluidic cell culture system in preparation for human organ on a chip

Development of microfluidic cell culture system in preparation for human organ on a chip

Injection molded open microfluidic well plate inserts for user-friendly coculture and microscopy.

Open microfluidic cell culture systems are powerful tools for interrogating biological mechanisms. We have previously presented a microscale cell culture system, based on spontaneous capillary flow of biocompatible hydrogels, that is integrated into a standard cell culture well plate, with flexible cell compartment geometries and easy pipet access. Here, we present two new injection molded open microfluidic devices that also easily insert into standard cell culture well plates and standard culture workflows, allowing seamless adoption by biomedical researchers. These platforms allow culture and study of soluble factor communication among multiple cell types, and the microscale dimensions are well-suited for rare primary cells. Unique advances include optimized evaporation control within the well, manufacture with reproducible and cost-effective rapid injection molding, and compatibility with sample preparation workflows for high resolution microscopy (following well-established coverslip mounting procedures). In this work, we present several use cases that highlight the usability and widespread utility of our platform including culture of limited primary testis cells from surgical patients, microscopy readouts including immunocytochemistry and single molecule fluorescence in situ hybridization (smFISH), and coculture to study interactions between adipocytes and prostate cancer cells.