Microphysiological testing for chemosensitivity of living tumor cells with multiparametric microsensor chips

Microfabricated electrochemical cell-based biosensors for analysis of living cells in vitro

Cellular biochemical parameters can be used to reveal the physiological and functional information of various cells. Due to demonstrated high accuracy and non-invasiveness, electrochemical detection methods have been used for cell-based investigation. When combined with improved biosensor design and advanced measurement systems, the on-line biochemical analysis of living cells in vitro has been applied for biological mechanism study, drug screening and even environmental monitoring. In recent decades, new types of miniaturized electrochemical biosensor are emerging with the development of microfabrication technology. This review aims to give an overview of the microfabricated electrochemical cell-based biosensors, such as microelectrode arrays (MEA), the electric cell-substrate impedance sensing (ECIS) technique, and the light addressable potentiometric sensor (LAPS). The details in their working principles, measurement systems, and applications in cell monitoring are covered. Driven by the need for high throughput and multi-parameter detection proposed by biomedicine, the development trends of electrochemical cell-based biosensors are also introduced, including newly developed integrated biosensors, and the application of nanotechnology and microfluidic technology.

Biosensors in clinical chemistry - 2011 update

Research activity and applications of biosensors for measurement of analytes of clinical interest over the last eight years are reviewed. Nanotechnology has been applied to improve performance of biosensors using electrochemical, optical, mechanical and physical modes of transduction, and to allow arrays of biosensors to be constructed for parallel sensing. Biosensors have been proposed for measurement of cancer biomarkers, cardiac biomarkers as well as biomarkers for autoimmune disease, infectious disease and for DNA analysis. Novel applications of biosensors include measurements in alternate sample types, such as saliva. Biosensors based on immobilized whole cells have found new applications, for example to detect the presence of cancer and to monitor the response of cancer cells to chemotherapeutic agents. The number of research reports describing new biosensors for analytes of clinical interest continues to increase; however, movement of biosensors from the research laboratory to the clinical laboratory has been slow. The greatest impact of biosensors will be felt at point-of-care testing locations without laboratory support. Integration of biosensors into reliable, easy-to-use and rugged instrumentation will be required to assure success of biosensor-based systems at the point-of-care.

Electrical characterization of single cells using polysilicon wire ion sensor in an isolation window

A polysilicon wire (PSW) sensor can detect the H(+) ion density (pH value) of the medium coated on its surface, and different cells produce different extracellular acidification and hence different H(+) ion densities. Based on this, we used a PSW sensor in combination with a mold-cast polydimethylsiloxane (PDMS) isolation window to detect the adhesion, apoptosis and extracellular acidification of single normal cells and single cancer cells. Single living human normal cells WI38, MRC5, and BEAS-2B as well as non-small-cell lung cancer (NSCLC) cells A549, H1299, and CH27 were cultivated separately inside the isolation window. The current flowing through the PSW channel was measured. From the PSW channel current change as a function of time, we determined the cell adhesion time by observing the time required for the current change to saturate, since a stable extracellular ion density was established after the cells were completely adhered to the PSW surface. The apoptosis of cells can also be determined when the channel current change drops to zero. We found that all the NSCLC cells had a higher channel current change and hence a lower pH value than the normal cells anytime after they were seeded. The corresponding average pH values were 5.86 for A549, 6.00 for H1299, 6.20 for CH27, 6.90 for BEAS-2B, 6.96for MRC5, and 7.02 for WI38, respectively, after the cells were completely adhered to the PSW surface. Our results show that NSCLC cells have a stronger cell-substrate adhesion and a higher extracellular acidification rate than normal cells.

Microfluidic Device with Integrated Glucose Sensor for Cell-Based Assay in Toxicology

We have developed a cell-based assay platform using a microfluidic device integrating a glucose sensor into a cell culture device with closed-loop perfusion. Online measurement of cell kinetic change associated with cell status change was achieved by measuring glucose concentration change in the device with a cell exposed to a toxic material. The cell-based assay platform, which is integrated with a sensor and a perfusion system, was expected to improve measurement accuracy and efficiency, leading to the discovery of new tools in such wide-ranging fields as drug discovery, life sciences, and medical research.

A Clark-type oxygen chip for in situ estimation of the respiratory activity of adhering cells

A Clark-type oxygen chip consisting of a polydimethylsiloxane (PDMS) reservoir containing an amino group-modified PDMS oxygen-permeable membrane (OPM) and a glass substrate containing a three-electrode detector has been constructed by using microfabrication techniques, and it is utilized for in situ measurement of the respiration activity of adhering cells. Use of the alginate sol electrolyte and the electroplating Ag/AgCl pseudo-reference electrode can effectively diminish the crosstalk between the electrochemical electrodes and supply a stable potential for the detection of dissolved oxygen, respectively. The Clark-type oxygen chips possess only 1.00% residual current, response time of 13.4s and good linearity with a correlation coefficient of 0.9933. The modification of amino groups for the OPM obviously facilitates the adhesion of HeLa cells onto the PDMS OPM surface and allows the cells to spread after 2h of incubation. The oxygen consumption of the cells in the cell-adhesion process increases with the adhesion time, and the increment of cellular oxygen consumption per minute reaches a maximum after 30 min of incubation. Moreover, the change in the respiration activity of adhering HeLa cells stimulated by the high concentration of glucose or propofol anaesthetic can be monitored in real time with the Clark-type oxygen chip.

Viability analysis and apoptosis induction of breast cancer cells in a microfluidic device: effect of cytostatic drugs

Breast cancer is the leading cause of cancer deaths among non-smoking women worldwide. At the moment the treatment regime is such that patients receive different chemotherapeutic and/or hormonal treatments dependent on the hormone receptor status, the menopausal status and age. However, in vitro sensitivity testing of tumor biopsies could rationalize and improve the choice of chemo- and hormone therapy. Lab-on-a-Chip devices, using microfluidic techniques, make detailed cellular analysis possible using fewer cells, enabling working with a patients’ own cells and performing chemo- and hormone sensitivity testing in an ex vivo setting. This article describes the development of two microfluidic devices made in poly(dimethylsiloxane) (PDMS) to validate the cell culture properties and analyze the chemosensitivity of MCF-7 cells (estrogen receptor positive human breast cancer cells) in response to the drug staurosporine (SSP). In both cases, cell viability was assessed using the life-stain Calcein-AM (CAAM) and the death dye propidium iodide (PI). MCF-7 cells could be statically cultured for up to 7 days in the microfluidic chip. A 30 min flow with SSP and a subsequent 24 h static incubation in the incubator induced apoptosis in MCF-7 cells, as shown by a disappearance of the aggregate-like morphology, a decrease in CAAM staining and an increase in PI staining. This work provides valuable leads to develop a microfluidic chip to test the chemosensitivity of tumor cells in response to therapeutics and in this way improve cancer treatment towards personalized medicine.

Methods and goals for the use of in vitro and in vivo chemosensitivity testing

Sensitive, specific, and accurate methods to assay chemosensitivity are needed to (1) screen new therapeutic agents, (2) identify patterns of chemosensitivity for different tumor types, (3) establish patterns of cross-resistance and sensitivity in treatment of naïve and relapsing tumors, (4) identify genomic and proteomic profiles associated with sensitivity, (5) correlate in vitro response with preclinical in vivo effects and clinical outcomes for a particular therapeutic agent, and (6) tailor chemotherapy regimens to individual patients. Various methods are available to achieve these end points, including several in vitro clonogenic and proliferation assays, cell metabolic activity assays, molecular assays to monitor expression of markers for responsiveness, drug resistance, and for induction of apoptosis, in vivo tumor growth and survival assays in metastatic and orthotopic models, and in vivo imaging assays. The advantages and disadvantages of the specific assays are discussed. A summary of research questions related to chemosensitivity testing is also included.

Dynamic analysis of metabolic effects of chloroacetaldehyde and cytochalasin B on tumor cells using bioelectronic sensor chips

PURPOSE

To study the interplay of drugs and energy metabolism of tumor cells, metabolic changes induced by chloroacetaldehyde and cytochalasin B were analyzed in colon carcinoma cells LS174T.

METHODS

O(2)-consumption and extracellular acidification were recorded using a bioelectronic sensor-chip system, which monitors these parameters in a culture continuously for at least 24 h. In parallel cultures cell number, cellular ATP-content, mitochondrial transmembrane potential, and the content of reactive oxygen species (ROS) were determined.

RESULTS

When cell death was induced by chloroacetaldehyde (50 muM), the rate of acidification declined gradually for the next 15 h, while O(2)-consumption decreased rapidly within 30 min. This correlated with a loss in mitochondrial potential. However, cellular ATP-level showed a transient increase at 2 h; also ROS levels increased up to 6 h. In cells treated with cytochalasin B (2 muM), which inhibits glucose uptake, the rate of O(2)-consumption increased and the acidification activity dropped, even upon glutamine depletion. Mitochondrial membrane potential transiently increased after 1 h, while ATP-content decreased; there was no change in the level of ROS.

CONCLUSION

The pattern of changes in basic energy metabolism differs with the type of cell death and growth inhibition involved in the cytotoxic action of two different drugs.

Analysis of Drug Action on Tumor Cell Metabolism Using Electronic Sensor Chips

Chemotherapeutic drugs affect the metabolism of tumor cells regardless of the specific target of action. Basic parameters of cell metabolism are extrusion of acids into the microenvironment and oxygen consumption. To analyze these changes on living cells in real-time, a test system based on multiparametric chips with an array of sensors for monitoring pH and O(2) as well as electric impedance has been developed. Cells are cultivated on these chips and supplied with medium by a fluid perfusion set-up which mimics microphysiological conditions and allows for drug addition and removal. Human colon carcinoma cells LS174T were used as a model to test the effect of drugs. Cells growing on chips were monitored for 24 h and longer. Untreated cells showed a continuous increase in the rate of acidification, while the rate of respiration remained fairly constant. Addition of chloroacetaldehyde (50 microM) rapidly attenuated O(2) consumption with a gradual decrease in acidification following. In contrast, with cisplatin (16.7 microM) a delayed and gradual decrease in both the rates of acidification and respiration effect occurred over 2-3 days. These results provide insights to the mechanisms of action of these drugs, which are coherent with those already known. Thus, multiparametric sensor chips provide elementary information on drug action.