Approach to a multiparametric sensor-chip-based tumor chemosensitivity assay

Comparison of Impedance-based Sensors for Cell Adhesion Monitoring and In Vitro Methods for Detecting Cytotoxicity Induced by Chemicals

The recent European Commission REACH (Registration, Evaluation and Authorisation of Chemicals) policy outlines a plan for toxicological testing by using alternative non-animal in vitro methods. In this context, there is a need to develop and standardise high-throughput screening (HTS) methods for studying the cytotoxicity induced by chemicals. Electrochemical impedance spectroscopy (EIS) can be considered as a complementary technique to alternative in vitro testing for studying cell adhesion to the substrate, and can give real-time and kinetic information on cell responses to a toxicant. This paper describes the development of a home-made chip based on impedance spectroscopy, and its application in studying the kinetics of BALB/3T3 cell adhesion and the cellular responses to a toxic product as a function of time. Concentrations of sodium arsenite, ranging from 10 microM up to 1000 microM, were tested in the system, and the results were compared with those obtained with standard protocols used to study basal cytotoxicity induced by chemicals in the BALB/3T3 cell line. The results show that the sensitivity of the developed chip was better than that with the MTT test, with the additional advantages of online monitoring.

Sensor Access to the Cellular Microenvironment Using the Sensing Cell Culture Flask

The Sensing Cell Culture Flask (SCCF) is a cell culture monitoring system accessing the cellular microenvironment in 2D cell culture using electrochemical microsensors. The system is based on microfabricated sensor chips embedded in standard cell culture flasks. Ideally, the sensor chips could be equipped with any electrochemical sensor. Its transparency allows optical inspection of the cells during measurement. The surface of the sensor chip is in-plane with the flask surface allowing undisturbed cell growth on the sensor chip. A custom developed rack system allows easy usage of multiple flasks in parallel within an incubator. The presented data demonstrates the application of the SCCF with brain tumor (T98G) and breast cancer (T-47D) cells. Amperometric oxygen sensors were used to monitor cellular respiration with different incubation conditions. Cellular acidification was accessed with potentiometric pH sensors using electrodeposited iridium oxide films. The system itself provides the foundation for electrochemical monitoring systems in 3D cell culture.

Pericellular oxygen monitoring with integrated sensor chips for reproducible cell culture experiments

OBJECTIVES

Here we present an application, in two tumour cell lines, based on the Sensing Cell Culture Flask system as a cell culture monitoring tool for pericellular oxygen sensing.

MATERIALS AND METHODS

T-47D (human breast cancer) and T98G (human brain cancer) cells were cultured either in atmospheric air or in a glove-box set at 4% oxygen, in both cases with 5% CO2 in the gas phase. Pericellular oxygen tension was measured with the help of an integrated sensor chip comprising oxygen sensor arrays.

RESULTS

Obtained results illustrate variation of pericellular oxygen tension in attached cells covered by stagnant medium. Independent of incubation conditions, low pericellular oxygen concentration levels, usually associated with hypoxia, were found in dense cell cultures.

CONCLUSIONS

Respiration alone brought pericellular oxygen concentration down to levels which could activate hypoxia-sensing regulatory processes in cultures believed to be aerobic. Cells in culture believed to experience conditions of mild hypoxia may, in reality, experience severe hypoxia. This would lead to incorrect assumptions and suggests that pericellular oxygen concentration readings are of great importance to obtain reproducible results when dealing with hypoxic and normoxic (aerobic) incubation conditions. The Sensing Cell Culture Flask system allows continuous monitoring of pericellular oxygen concentration with outstanding long-term stability and no need for recalibration during cell culture experiments. The sensor is integrated into the flask bottom, thus in direct contact with attached cells. No additional equipment needs to be inserted into the flask during culturing. Transparency of the electrochemical sensor chip allows optical inspection of cells attached on top of the sensor.

Sensor-based cell and tissue screening for personalized cancer chemotherapy

Personalized tumor chemotherapy depends on reliable assay methods, either based on molecular "predictive biomarkers" or on a direct, functional ex vivo assessment of cellular chemosensitivity. As a member of the latter category, a novel high-content platform is described monitoring human mamma carcinoma explants in real time and label-free before, during and after an ex vivo modeled chemotherapy. Tissue explants are sliced with a vibratome and laid into the microreaction chambers of a 24-well sensor test plate. Within these ~23 μl volume chambers, sensors for pH and dissolved oxygen record rates of cellular oxygen uptake and extracellular acidification. Robot-controlled fluid system and incubation are parts of the tissue culture maintenance system while an integrated microscope is used for process surveillance. Sliced surgical explants from breast cancerous tissue generate well-detectable ex vivo metabolic activity. Metabolic rates, in particular oxygen consumption rates have a tendency to decrease over time. Nonetheless, the impact of added drugs (doxorubicin, chloroacetaldehyde) is discriminable. Sensor-based platforms should be evaluated in explorative clinical studies for their suitability to support targeted systemic cancer therapy. Throughput is sufficient for testing various drugs in a range of concentrations while the information content obtained from multiparametric real-time analysis is superior to conventional endpoint assays.

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.

The Bionas technology for anticancer drug screening

BACKGROUND

The Bionas 2500(®) analyzing system is an advanced label-free technology using a cell-based multi-sensor array, which is commercially available. Data on metabolism, respiration, adhesion, cell proliferation and cell death rates, as well as ligand-receptor interactions (multi-parametric) can be acquired and statistically evaluated. Noteworthy is the possibility of analyzing later after effects and/or recovery after drug treatment. In addition, Bionas supports all conceivable drug application modes (one, two or more drugs). Specimens for drug screening with Bionas consist of human permanent cell lines, primary cell cultures as well as 'tumor slices' obtained from biopsies and surgery material.

OBJECTIVE/METHODS

Examples of measurements are presented and discussed.

CONCLUSION

Although drug throughput is modest, the high quality of the information allows in-depth evaluation.

Randomized phase II trial of concurrent cisplatin-radiotherapy with or without neoadjuvant docetaxel and cisplatin in advanced nasopharyngeal carcinoma

PURPOSE

To compare the toxicities, tumor control, survival, and quality of life of nasopharyngeal cancer (NPC) patients treated with sequential neoadjuvant chemotherapy followed by concurrent cisplatin-radiotherapy (CRT) or CRT alone.

PATIENTS AND METHODS

Previously untreated stage III to IVB NPC were randomly assigned to (1) neoadjuvant docetaxel 75 mg/m(2) and cisplatin 75 mg/m(2) every 3 weeks for two cycles, followed by cisplatin 40 mg/m(2)/wk concurrent with radiotherapy, or (2) CRT alone. Planned accrual was 30 patients per arm to detect 20% difference of toxicities based on 95% CIs.

RESULTS

From November 2002 to November 2004, 65 eligible patients were randomly assigned to neoadjuvant chemotherapy followed by CRT (n = 34) or CRT alone (n = 31). There was a high rate of grade 3/4 neutropenia (97%) but not neutropenic fever (12%) during neoadjuvant chemotherapy. No significant differences in rates of acute toxicities were observed between the two arms during CRT. Dose intensities of concurrent cisplatin, late RT toxicities and quality of life scores were comparable in both arms. The 3-year progression-free survival for neoadjuvant versus control arm was 88.2% and 59.5% (hazard ratio = 0.49; 95% CI, 0.20 to 1.19; P = .12). The 3-year overall survival for neoadjuvant versus control arm was 94.1% and 67.7% (hazard ratio = 0.24; 95% CI, 0.078 to 0.73; P = .012).

CONCLUSION

Neoadjuvant docetaxel-cisplatin followed by CRT was well tolerated with a manageable toxicity profile that allowed subsequent delivery of full-dose CRT. Preliminary results suggested a positive impact on survival. A phase III study to definitively test this neoadjuvant-concurrent strategy is warranted.

Assessment of cytotoxicity by impedance spectroscopy

This paper describes a simple and convenient method to monitor on-line cell adhesion by electrical impedance measurements. Immortalized mouse fibroblasts, BALB/3T3, were cultured onto interdigitated electrode structures integrated into the bottom of an in-house fabricated device. Impedance modulus, phase, real and imaginary parts were considered separately and plotted as function of frequency and time to better understand and select the component giving more information on cell adhesion changes. For cytotoxicity assessment, the cells were treated with different concentrations of sodium arsenite used as model toxicant and their responses were monitored on-line. The half inhibition concentration, the required concentration to achieve 50% inhibition, derived from the measurements fall between the results obtained using standard 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide test and colony forming efficiency assay confirming the good sensitivity of the system. In term of impedance signal, the modulus results was found to be the most sensitive of the considered components for cytotoxicity testing of chemicals.

The use of a fluorescence-based oxygen uptake assay in the analysis of cytotoxicity

Cellular oxygen uptake is an informative parameter of cellular function but is not measured routinely in the analysis of cytotoxicity. Here we have evaluated the ability of a fluorescence-based oxygen uptake assay to assess the metabolic activity of common adherent cells including HepG2, LLC-PK1, Hek293T, C2C12, H-4-II-E, and primary rat hepatocytes. The assay employs water-soluble phosphorescent oxygen probes, analysed in standard 96-well plates on a conventional fluorescence plate reader. Using this respirometric method, cellular responses to known toxicants were examined and results compared to those obtained using established cell viability assays such as MTT, LDH and CyQuant. Respirometric analysis successfully detected these cytotoxic insults with responses being influenced by both mode of toxicity and the biochemical characteristics of the individual cell line. Results indicate that the oxygen uptake assay was more sensitive to the impairment of mitochondrial function than the other assays used. In conjunction with assays analysing other biomarkers of cytotoxicity, a more detailed picture of cell response to drug treatment can be obtained.

Optical technologies for the read out and quality control of DNA and protein microarrays

Microarray formats have become an important tool for parallel (or multiplexed) monitoring of biomolecular interactions. Surface-immobilized probes like oligonucleotides, cDNA, proteins, or antibodies can be used for the screening of their complementary targets, covering different applications like gene or protein expression profiling, analysis of point mutations, or immunodiagnostics. Numerous reviews have appeared on this topic in recent years, documenting the intriguing progress of these miniaturized assay formats. Most of them highlight all aspects of microarray preparation, surface chemistry, and patterning, and try to give a systematic survey of the different kinds of applications of this new technique. This review places the emphasis on optical technologies for microarray analysis. As the fluorescent read out of microarrays is dominating the field, this topic will be the focus of the review. Basic principles of labeling and signal amplification techniques will be introduced. Recent developments in total internal reflection fluorescence, resonance energy transfer assays, and time-resolved imaging are addressed, as well as non-fluorescent imaging methods. Finally, some label-free detection modes are discussed, such as surface plasmon microscopy or ellipsometry, since these are particularly interesting for microarray development and quality control purposes.

Fluorescence based oxygen uptake analysis in the study of metabolic responses to apoptosis induction

Mitochondrial activity has been shown to be centrally involved in the progression of apoptosis. The electron transport chain is a major player in this process and oxygen uptake analysis provides detailed information on its activity. Here we examined the ability of a fluorescence based oxygen uptake assay to inform on cellular responses to apoptosis induction. HL60 cells treated with camptothecin and UV light were used as a model and the ability of the assay to detect dose and time dependent decreases in respiratory activity analysed. The data obtained were compared to more specific markers of apoptosis including annexin V binding, and caspase-3 activity. Reductions in oxygen uptake rates were seen at lower doses than increases in annexin V binding or mitochondrial membrane potential depolarisation. These reductions were observed earlier than detectable caspase-3 activity and were unaffected by pre-treatment with the caspase-3 inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoro-methylketone (zVADfmk).

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.

Multi-channel 3-D cell culture device integrated on a silicon chip for anticancer drug sensitivity test

A novel three-dimensional cell culture system was constructed with an array of cell panels (4 x 5) in a silicon chip, together with multi-channel drug containers. Human breast cancer (MCF-7) cells were embedded in a collagen-gel matrix and entrapped in a pyramidal-shaped silicon hole. Each cell panel can be isolated by a channel composed of a microfluid part and a reservoir. A cell panel was exposed to 200 mm KCN for 2 days to demonstrate that each cell panel could be independently evaluated under various stimulation conditions. Based on the cellular respiration activity, the proliferation behavior was continuously monitored on the silicon-based cell array for 5 days using scanning electrochemical microscopy (SECM). The cells entrapped in the device (3-D culture) proliferated normally, and the proliferation rate was lower than that of cells grown in a monolayer cell culture (2-D culture). The effects of three anticancer drugs measured simultaneously on the cell chip were in good agreement with those obtained by a conventional colorimetric assay. Our results suggest that the silicon-based device for 3D culture is appropriate for a chemosensitivity assay involving multi-chemical stimulation.

Induction of apoptosis and effect on CD20+ using rituximab on autologous peripheral blood stem cell harvests from patients with B cell lymphomas

Purging of neoplastic cells for autologous stem cell transplantation is usually done in vivo by administering chemotherapy and/or other agents before harvesting. It is also possible to decrease malignant cells counts directly in the cell harvest. In this study, we ascertained the effect of anti-CD20 monoclonal antibody and rituximab administration on peripheral blood hematopoietic stem cells. Five samples of stem cell harvests from different patients with B cell lymphoma were obtained. Each sample was divided in two tubes with calcium gluconate (20 mEq/50 microl). Rituximab (1 mg/600,000 mononuclear cells) was added to one of the tubes. Using flow cytometry, CD19, CD20 (B cell markers), and CD95 (apoptosis marker), expression was measured at baseline and 24 h after the addition of rituximab. A one-sided t-test with equal variances was used to analyze the results. Immediately after rituximab addition, CD20 expression became null. No significant difference in variation of CD19 expression was detected after the addition of rituximab (-3.64% control vs. 0.63% rituximab, p = 0.69). Mean variations of percentage of CD95 expression were 2.9% (controls) and 10.52% (rituximab tubes) (p = 0.06). We conclude that rituximab is capable of initiating apoptosis in vitro. We found no decrease in the CD19+ cell count, used as a surrogate marker for CD20+ cells, meaning that, at least in 24 h, apoptosis activation is not capable of decreasing CD20+ cell numbers. In vitro purging of peripheral blood stem cells harvests with rituximab could be part of a broader therapeutic strategy to be offered to lymphoproliferative disorder patients.

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.

A phase II study of docetaxel in patients with metastatic carcinoid tumors

Twenty-one patients with metastatic carcinoid tumors were treated with docetaxel. Although the treatment was well tolerated, no objective radiologic responses were observed. Novel, more effective agents are needed for this disease.

BACKGROUND

Traditional combination chemotherapy regimens containing streptozocin, doxorubicin, and 5-fluorouracil have yielded disappointing results in patients with metastatic carcinoid tumors. The lack of efficacy of these combinations, together with their toxicity, has led to efforts to investigate therapeutic agents that are potentially more active and tolerable. We, therefore, assessed the efficacy of docetaxel in the treatment of patients with metastatic carcinoid tumors.

METHODS

Twenty-one patients with metastatic carcinoid tumors were treated with docetaxel, administered at a dose of 75 mg/m2 every three weeks. Patients were followed for evidence of toxicity, response, and survival.

RESULTS

Docetaxel was well tolerated in this patient population. However, no objective radiologic responses were noted in any of the 21 patients. Of the 13 patients who were evaluable for biochemical responses to therapy, four (31%) experienced decreases in 24-hour urinary 5-hydroxyindole acetic acid (5HIAA) excretion of greater than 50%. The clinical course of the patients enrolled in this study was marked by a high incidence of radiologically stable disease (81%), a median progression-free survival time of 10 months, and a median overall survival time of 24 months.

CONCLUSION

Although treatment with docetaxel results in biochemical responses in patients with metastatic carcinoid tumors, the lack of more significant antitumor activity demonstrates the need for novel, more effective agents in this disease.

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

A constraint in the reliability of predictive chemosensitivity assays is linked to the fact that they analyze only a single cellular or biochemical parameter. A multiparametric test system using microsensor chips has been developed which can detect online microphysiological changes in living cells. Tumor cells were grown directly on glass- or silicon-based electronic sensor chips. Changes in extracellular pH and pO(2), reflecting metabolic activities, and changes in impedance, reflecting morphological properties, were monitored. In this study, colon and breast cancer cells as well as doxorubicin-sensitive and doxorubicin-resistant sarcoma cell lines were exposed to cytochalasin B, chloroacetaldehyde, or doxorubicin. Results show (1) reduction in medium acidification, (2) marked and rapid changes in O(2) consumption, and (3) modulations in impedance correlating with morphological changes observed in the microscope. Drug-resistant cells do not show these changes. Therefore, this microphysiological monitoring is a versatile tool for chemosensitivity testing of tumor cells.

Relevance of tumor microenvironment for progression, therapy and drug development

Tumor interstitium exhibits a microenvironment that differs from corresponding normal tissues. Tumor phenotype shows, for example, an elevated intracellular pH (pHi), a lowered extracellular pH (pHe), a low oxygen concentration and low glucose levels. These differences are caused by cell biological (so called intrinsic) factors, e.g. a higher acidification rate, as well as by more systemic (extrinsic) factors, e.g. poor tumor vascularization. They represent important factors for invasiveness, immune suppression and proliferation, and they imply possibilities for diagnosis, prognosis and therapy. We have developed an experimental data-based computer model, which has simulated the potential role of metabolic effects on tumor progression. We show an experiment on cellular metabolism demonstrating the immunosuppressive impact of low pHe on peripheral blood mononuclear cells. Finally, we review important findings on the tumor microenvironment leading to possibilities for therapy which are currently evolving and which promise higher effectiveness for cancer therapy.

Multiparametric sensor chips for chemosensitivity testing of sensitive and resistant tumor cells

Many different assays have been developed for testing the chemosensitivity of tumor cells in vitro, usually based on a single biochemical or cellular parameter. A multiparametric test system has been developed that accommodates on a single chip numerous sensors for metabolic parameters, deltapH and deltapO2, as well as for morphological changes. The cells grow directly on the chips and can be continuously monitored online up to several days. The effects of various chemotherapeutic drugs on the metabolic profile of several tumor cell lines have been investigated. In colon carcinoma-derived LS174T cells, cytochalasin B markedly increased oxygen consumption while decreasing the rate of extracellular acidification. These effects, which reflect the biochemical action of cytochalasin B, were reversible on drug removal. In contrast, chloroacetaldehyde markedly reduced respiration, which recovered when the drug was removed. Primary breast cancer cells also responded to chloroacetaldehyde with a marked reduction in deltapO2, followed by a reduced rate of acidification. Comparing the metabolism of doxorubicin-sensitive and -resistant mouse sarcoma S180 cells, the rates of acidification and respiration were inhibited by doxorubicin only in the sensitive cells, whereas in the resistant cells oxygen consumption even increased. These examples demonstrate that this chip-based test system provides rapid and important information for assessing chemosensitivity of tumor cells.

Chemosensitivity testing of human tumors using Si-sensor chips

Chemotherapy is, on its own or in combination with other treatments, a very effective anticancer therapy. Introduced in the middle of the last century, chemotherapy today still faces the problem of determining which specific agent or agents are able to yield the desired clinical therapeutical effect for a particular tumor and patient. Numerous tests in vitro have been developed to detect chemosensitivity and chemoresistance and also for screening new drugs. Three groups of tests can be defined: 1, cell viability tests; 2, measurements of cell metabolism; and 3, clonogenic assays. Test time, tissue preparation, complexity of test performance, and correlation with the clinical progress of the disease are criteria used to judge how successful the tests are. The introduction of Si-sensor chips, which are able to detect metabolic changes in living cells, has opened up new possibilities in this field. Basically two sensor principles or types can be considered: (a) the light-addressed potentiometric sensor (LAPS) and (b) the multisensor array (MSA). Whereas LAPS measures one, MSA registers online many parameters (for instance, impedance, pH, O2, temperature). The aim of this chapter is to review this technology and to present recent applications using cells, tissue slices, and biopsies.