Mini chamber system for long-term maintenance and observation of cultured cells

Facilitating long-term cell examinations and time-lapse recordings in cell biology research with CO2 mini-incubators

In recent years, microscopy has revolutionized the study of dynamic living cells. However, performing long-term live cell imaging requires stable environmental conditions such as temperature, pH, and humidity. While standard incubators have traditionally provided these conditions, other solutions, like stagetop incubators are available. To further enhance the accessibility of stable cell culture environments for live cell imaging, we developed a portable CO2 cell culture mini-incubator that can be easily adapted to any x-y inverted microscope stage, enabling long-term live cell imaging. This mini-incubator provides and maintains stable environmental conditions and supports cell viability comparable to standard incubators. Moreover, it allows for parallel experiments in the same environment, saving both time and resources. To demonstrate its functionality, different cell lines (VERO and MDA-MB-231) were cultured and evaluated using various assays, including crystal violet staining, MTT, and flow cytometry tests to assess cell adhesion, viability, and apoptosis, respectively. Time-lapse imaging was performed over an 85-h period with MDA-MB-231 cells cultured in the mini-incubator. The results indicate that this device is a viable solution for long-term imaging and can be applied in developmental biology, cell biology, and cancer biology research where long-term time-lapse recording is required.

Automated Multichamber Time-lapse Videography for Long-term In Vivo Observation of Migrating Cells

AIM

To observe and document the migration of living cells by time-lapse videography, we constructed a low-budget system based on a common inverted microscope.

MATERIALS AND METHODS

Long-term observation of six-well plates is enabled through maintenance of cell culture conditions (5% CO₂ in air at 37°C). Points of interest can be revisited in definable intervals with <1 μm repositioning error. Digital photographs from each programmed time point are paired with environmental data and combined into a record.

RESULTS

We used this new chamber to observe the migration of various cell lines. The design represents a good compromise between low cost and good precision. Detailed analyses verified that the environmental conditions were appropriately maintained, enabling long-term observation of viable cells. The stimulating influence of irradiation with photons (radiotherapy) on cellular motility of glioblastoma cells is presented.

CONCLUSION

This study demonstrates that useful videographic systems can be constructed at low cost.

Low-cost motility tracking system (LOCOMOTIS) for time-lapse microscopy applications and cell visualisation

Direct visualisation of cells for the purpose of studying their motility has typically required expensive microscopy equipment. However, recent advances in digital sensors mean that it is now possible to image cells for a fraction of the price of a standard microscope. Along with low-cost imaging there has also been a large increase in the availability of high quality, open-source analysis programs. In this study we describe the development and performance of an expandable cell motility system employing inexpensive, commercially available digital USB microscopes to image various cell types using time-lapse and perform tracking assays in proof-of-concept experiments. With this system we were able to measure and record three separate assays simultaneously on one personal computer using identical microscopes, and obtained tracking results comparable in quality to those from other studies that used standard, more expensive, equipment. The microscopes used in our system were capable of a maximum magnification of 413.6×. Although resolution was lower than that of a standard inverted microscope we found this difference to be indistinguishable at the magnification chosen for cell tracking experiments (206.8×). In preliminary cell culture experiments using our system, velocities (mean µm/min ± SE) of 0.81 ± 0.01 (Biomphalaria glabrata hemocytes on uncoated plates), 1.17 ± 0.004 (MDA-MB-231 breast cancer cells), 1.24 ± 0.006 (SC5 mouse Sertoli cells) and 2.21 ± 0.01 (B. glabrata hemocytes on Poly-L-Lysine coated plates), were measured and are consistent with previous reports. We believe that this system, coupled with open-source analysis software, demonstrates that higher throughput time-lapse imaging of cells for the purpose of studying motility can be an affordable option for all researchers.

A novel environmental chamber for neuronal network multisite recordings

Environmental stability is a critical issue for neuronal networks in vitro. Hence, the ability to control the physical and chemical environment of cell cultures during electrophysiological measurements is an important requirement in the experimental design. In this work, we describe the development and the experimental verification of a closed chamber for multisite electrophysiology and optical monitoring. The chamber provides stable temperature, pH and humidity and guarantees cell viability comparable to standard incubators. Besides, it integrates the electronics for long-term neuronal activity recording. The system is portable and adaptable for multiple network housings, which allows performing parallel experiments in the same environment. Our results show that this device can be a solution for long-term electrophysiology, for dual network experiments and for coupled optical and electrical measurements.

Microfluidic devices for studying heterotypic cell-cell interactions and tissue specimen cultures under controlled microenvironments

Microfluidic devices allow for precise control of the cellular and noncellular microenvironment at physiologically relevant length- and time-scales. These devices have been shown to mimic the complex in vivo microenvironment better than conventional in vitro assays, and allow real-time monitoring of homotypic or heterotypic cellular interactions. Microfluidic culture platforms enable new assay designs for culturing multiple different cell populations and∕or tissue specimens under controlled user-defined conditions. Applications include fundamental studies of cell population behaviors, high-throughput drug screening, and tissue engineering. In this review, we summarize recent developments in this field along with studies of heterotypic cell-cell interactions and tissue specimen culture in microfluidic devices from our own laboratory.

Chamber and microfluidic probe for microperfusion of organotypic brain slices

Microfluidic systems are increasingly being used for the culture and study of dissociated cells because they require only minute amounts of materials while enabling drug screening and chemotaxis studies down to the single cell level. However, the culture of organized tissue, such as brain slices, has been more difficult to adapt to microfluidic devices. Here, we present a microfluidic system, comprising (i) a perfusion chamber for the culture of organotypic slices that is compatible with high resolution imaging on inverted microscopes, and (ii) a novel transparent microfluidic probe (MFP) for the localized microperfusion of the brain tissue. The MFP is made in poly(dimethylsiloxane), features six micrometre-scale apertures and can be assembled within a few hours in a standard laboratory. Each aperture can indiscriminately be used either for the injection or aspiration of solutions, giving rise to many possible combinations. The MFP was successfully used for the perfusion of a small number of cells in a brain slice with concurrent confocal fluorescence imaging of the perfused dye and sub-cellular structures within the tissue.

Live cell tracking based on cellular state recognition from microscopic images

The analysis of cell motion is an essential process in fundamental medical studies because most active cellular functions involve motion. In this paper, a computer-assisted motion analysis system is proposed for cell tracking. In the proposed tracking process, unlike in conventional tracking methods, cellular states referring to the cellular life cycle are defined and appropriate strategies are adopted for cells at different states. The use of cellular state recognition allows detection of possible cell division and hence can improve the robustness of cell tracking. Experimental results show that cells can be successfully segmented and tracked over a long period of time, and the proposed system is found to be as accurate as manual tracking. Various quantitative analyses and visualizations are used to represent cell motion, which demonstrates the usefulness of the proposed system in the study of cell dynamics.

Replica-moulded polydimethylsiloxane culture vessel lids attenuate osmotic drift in long-term cell cultures

An imbalance in medium osmolarity is a determinant that affects cell culture longevity. Even in humidified incubators, evaporation of water leads to a gradual increase in osmolarity over time. We present a simple replica-moulding strategy for producing self-sealing lids adaptable to standard, small-size cell-culture vessels. They are made of polydimethylsiloxane (PDMS), a flexible, transparent and biocompatible material, which is gas-permeable but largely impermeable to water. Keeping cell cultures in a humidified 5% CO2 incubator at 37 degrees C, medium osmolarity increased by +6.86 mosmol/kg/day in standard 35 mm Petri dishes, while PDMS lids attenuated its rise by a factor of four to changes of +1.72 mosmol/kg/ day. Depending on the lid membrane thickness,pH drifts at ambient CO2 levels were attenuated by a factor of 4 to 9. Comparative evaporation studies at temperatures below 60 degrees C yielded a 10-fold reduced water vapour flux of 1.75 g/day/ dm 2 through PDMS lids as compared with 18.69 g/day/dm 2 with conventional Petri dishes. Using such PDMS lids,about 2/3 of the cell cultures grew longer than 30 days in vitro. Among these,the average survival time was 69 days with the longest survival being 284 days under otherwise conventional cell culture conditions.

Microchips for cell-based assays

Analysis of cells is a cornerstone in biomedical research. Traditional methods for cell culture and tissue analysis can be replaced by various microchips as discussed in this chapter. A tissue array is an example of microchip that provides higher throughput of tissue analysis. Other microchips provide completely new functionalities for the researcher. One such example that will be discussed is cell culture chips. The cell culture vessel will be much more competent for studies of cell and will enable real-time monitoring of cell behavior and gene expression at a single cell level, have possibilities for studying chemotaxis and shear stress phenomena in a controlled manner, provide least tissue-like culture conditions by providing micro 3D structures, and provide arrays of integrated detectors. Tissue arrays and the simplest forms of cell culture chips are commercialized today, and we may expect a large activity in this field in the future.

A transparent cell-culture microchamber with a variably controlled concentration gradient generator and flow field rectifier

Real-time observation of cell growth provides essential information for studies such as cell migration and chemotaxis. A conventional cell incubation device is usually too clumsy for these applications. Here we report a transparent microfluidic device that has an integrated heater and a concentration gradient generator. A piece of indium tin oxide (ITO) coated glass was ablated by our newly developed visible laser-induced backside wet etching (LIBWE) so that transparent heater strips were prepared on the glass substrate. A polymethylmethacrylate (PMMA) microfluidic chamber with flow field rectifiers and a reagent effusion hole was fabricated by a CO(2) laser and then assembled with the ITO heater so that the chamber temperature can be controlled for cell culturing. A variable chemical gradient was generated inside the chamber by combining the lateral medium flow and the flow from the effusion hole. Successful culturing was performed inside the device. Continuous long-term (>10 days) observation on cell growth was achieved. In this work the flow field, medium replacement, and chemical gradient in the microchamber are elaborated.

Encapsulated Petri dish system for single-cell drug delivery and long-term time lapse microscopy

We have developed a system that allows focal drug application for cell culture microscopy. Single-cell drug delivery is achieved through the insertion of a patch-clamp-like micropipette in a microenvironment-controlled chamber mounted on a standard 35-mm Petri dish. The system has precise control of temperature, CO(2) concentration, and humidity, while preventing contamination during experiments. The use of standard Petri dishes allows long-term experiments by alternating in situ microscopy with incubator growth. Modern biological long-term experiments such as the characterization of drug effects on cell movement, axonal guidance, mitosis, apoptosis, differentiation, or volume regulation can be performed. The chamber is compatible with any inverted microscope without significant modifications.

Applications of microfluidics for neuronal studies

Microfabrication processes have changed the technology used in consumer goods, and have now advanced into applications in biology. Microfluidic platforms are microfabricated tools that are gaining popularity for studies of molecular and cellular biology. These platforms can allow precise control of the environment surrounding individual cells and they have been used to study physiologic and pharmacologic responses at the single-cell level. This article reviews microfluidic technology with emphasis on advances that could apply to the study of the nervous system, including architecture for isolation of axons, integrated electrophysiology, patterned physical and chemical substrate cues, and devices for the precisely controlled delivery of possible therapeutic agents such as trophic factors and drugs. The potential of these chips for the study of neurological diseases is also discussed.

Continuously Microscopically Observed and Process-Controlled Cell Culture Within the SlideReactor: Proof of a New Concept for Cell Characterization

Certain cell types, especially primary human cells, favor a well-defined culture environment offering continuous supply of nutrients and oxygen and waste product removal. Several bioreactors based on special matrices or hollow fibers have been developed that provide such conditions. However, characterization of matrix re-organization or growth of tissue within these systems is possible only after culture termination. Evaluation of the influence of certain medium additives or culture conditions (e.g., temperature, oxygenation) on cell viability, expansion, and differentiation within these systems remains a challenging task. The SlideReactor, a miniaturized hollow fiber-based bioreactor, was developed to enable the observation of cells during culture. An operation concept offering predefined conditions for various cell types has been designed. For proof of concept, primary human cells (hepatocytes, fibroblasts, keratinocytes) and cell lines (HepG2, HuH7, C3A, WiDr, SkHep1) were cultured and observed. A series of experiments (n=40) showed the feasibility of the set-up; determination of process parameters and continuous observation is possible. The SlideReactor may serve as a simple and cost-efficient tool for cell characterization and optimization of cell-culture conditions.

Viability study of HL60 cells in contact with commonly used microchip materials

This paper presents a study in which different commonly used microchip materials (silicon oxide, borosilicate glass, and PDMS) were analyzed for their effect on human promyelocytic leukemic (HL60) cells. Copper-coated silicon was analyzed for its toxicity and therefore served as a positive control. With quantitative PCR, the expression of the proliferation marker Cyclin D1 and the apoptosis marker tissue transglutaminase were measured. Flow cytometry was used to analyze the distribution through the different phases of the cell cycle (propidium iodide, PI) and the apoptotic cascade (Annexin V in combination with PI). All microchip materials, with the exception of Cu, appeared to be suitable for HL60 cells, showing a ratio apoptosis/proliferation (R(ap)) comparable to materials used in conventional cell culture (polystyrene). These results were confirmed with cell cycle analysis and apoptosis studies. Precoating the microchip material surfaces with serum favor the proliferation, as demonstrated by a lower R(ap) as compared to uncoated surfaces. The Cu-coated surface appeared to be toxic for HL60 cells, showing over 90% decreased viability within 24 h. From these results, it can be concluded that the chosen protocol is suitable for selection of the cell culture material, and that the most commonly used microchip materials are compatible with HL60 culturing.

A biocompatible micro cell culture chamber (microCCC) for the culturing and on-line monitoring of eukaryote cells

We have previously shown that a polymeric (PMMA) chip with medium perfusion and integrated heat regulation provides sufficiently precise heat regulation, pH-control and medium exchange to support cell growth for weeks. However, it was unclear how closely the cells cultured in the chip resembled cells cultured in the culture flask. In the current study, gene expression profiles of cells cultured in the chip were compared with gene expression profiles of cells cultured in culture flasks. The results showed that there were only two genes that were differently expressed in cells grown in the cell culture chip compared to cell culture flasks. The cell culture chip could without further modification support cell growth of two other cell lines. Light coming from the microscope lamp during optical recordings of the cells was the only external factor identified, that could have a negative effect on cell survival. Low grade light exposure was however compatible with optical recordings as well as cell viability. These results strongly indicate that a cell culture chip could be constructed that allowed for on-line optical recording of cellular events without affecting the cell culturing condition compared to cell cultured in culture flasks incubated in a dark and CO2 conditioned incubator.

Handheld recirculation system and customized media for microfluidic cell culture

A palm-sized microfluidic recirculation system and customized media enable simplified long-term culture and imaging of cells. The combination of bare Braille display modules, a leveled monolithic surface for complete chip mounting, and a transparent heater improved portability, mechanical stability and optical accessibility. Modification of basal culture media with Leibovitz's L-15 medium enabled an incubator-free culture of carbonate-dependent cells by eliminating the need for exogenous carbon dioxide. This capability is demonstrated through time-lapse recording of proliferation of C2C12 myoblasts and MC3T3-E1 osteoblasts for over 2 weeks in ambient atmosphere without medium exchange. The method opens up new possibilities for portable cell culture and for long-term continuous visual monitoring of cells.

Co-expression of RON and MET is a prognostic indicator for patients with transitional-cell carcinoma of the bladder

Recepteur d'Origine Nantais (RON) is a distinct receptor tyrosine kinase in the c-met proto-oncogene family. We examined the mutational and expression patterns of RON in eight human uroepithelial cell lines. Biological effects of RON overexpression on cancer cells were investigated in vitro, and the prognostic significance of RON and/or c-met protein (MET) expression was analysed in a bladder cancer cohort (n=183). There was no evidence of mutation in the kinase domain of RON. Overexpression of RON using an inducible Tet-off system induced increased cell proliferation, motility, and antiapoptosis. Immunohistochemical analysis showed that RON was overexpressed in 60 cases (32.8%) of primary tumours, with 14 (23.3%) showing a high level of expression. Recepteur d'Origine Nantais expression was positively associated with histological grading, larger size, nonpapillary contour, and tumour stage (all P<0.01). In addition, MET was overexpressed in 82 cases (44.8%). Co-expressed RON and MET was significantly associated with decreased overall survival (P=0.005) or metastasis-free survival (P=0.01) in 35 cases (19.1%). Recepteur d'Origine Nantais-associated signalling may play an important role in the progression of human bladder cancer. Evaluation of RON and MET expression status may identify a subset of bladder-cancer patients who require more intensive treatment.