Arum Han

Quantification of the Heterogeneity in Breast Cancer Cell Lines Using Whole-Cell Impedance Spectroscopy

Purpose: Quantification of the heterogeneity of tumor cell populations is of interest for many diagnostic and therapeutic applications, including determining the cancerous stage of tumors. We attempted to differentiate human breast cancer cell lines from different pathologic stages and compare that with a normal human breast tissue cell line by characterizing the impedance properties of each cell line. Experimental Design: A microelectrical impedance spectroscopy system has been developed that can trap a single cell into an analysis cavity and measure the electrical impedance of the captured cell over a frequency range from 100 Hz to 3.0 MHz. Normal human breast tissue cell line MCF-10A, early-stage breast cancer cell line MCF-7, invasive human breast cancer cell line MDA-MB-231, and metastasized human breast cancer cell line MDA-MB-435 were used. Results: The whole-cell impedance signatures show a clear difference between each cell line in both magnitude and phase of the electrical impedance. The membrane capacitance calculated from the impedance data was 1.94 ± 0.14, 1.86 ± 0.11, 1.63 ± 0.17, and 1.57 ± 0.12 μF/cm2 at 100 kHz for MCF-10A, MCF-7, MDA-MB-231, and MDA-MB-435, respectively. The calculated resistance for each cancer cell line at 100 kHz was 24.8 ± 1.05, 24.8 ± 0.93, 24.9 ± 1.12, and 26.2 ± 1.07 MOhm, respectively. The decrease in capacitances of the cancer cell lines compared with that of the normal cell line MCF-10A was 4.1%, 16.0%, and 19.1%, respectively, at 100 kHz. Conclusions: These findings suggest that microelectrical impedance spectroscopy might find application as a method for quantifying progression of cancer cells without the need for tagging or modifying the sampled cells.

Microfabricated Microbial Fuel Cell Arrays Reveal Electrochemically Active Microbes

Microbial fuel cells (MFCs) are remarkable “green energy” devices that exploit microbes to generate electricity from organic compounds. MFC devices currently being used and studied do not generate sufficient power to support widespread and cost-effective applications. Hence, research has focused on strategies to enhance the power output of the MFC devices, including exploring more electrochemically active microbes to expand the few already known electricigen families. However, most of the MFC devices are not compatible with high throughput screening for finding microbes with higher electricity generation capabilities. Here, we describe the development of a microfabricated MFC array, a compact and user-friendly platform for the identification and characterization of electrochemically active microbes. The MFC array consists of 24 integrated anode and cathode chambers, which function as 24 independent miniature MFCs and support direct and parallel comparisons of microbial electrochemical activities. The electricity generation profiles of spatially distinct MFC chambers on the array loaded with Shewanella oneidensis MR-1 differed by less than 8%. A screen of environmental microbes using the array identified an isolate that was related to Shewanella putrefaciens IR-1 and Shewanella sp. MR-7, and displayed 2.3-fold higher power output than the S. oneidensis MR-1 reference strain. Therefore, the utility of the MFC array was demonstrated.

Development and Characterization of Microfluidic Devices and Systems for Magnetic Bead-Based Biochemical Detection

This paper presents the development and characterization of a generic microfluidic system for magnetic bead-based biochemical detection. Microfluidic and electrochemical detection devices such as microvalves, flow sensors, biofilters, and immunosensors have been successfully developed and individually characterized in this work. Magnetically driven microvalves, pulsed-mode microflow sensors, magnetic particle separators as biofilters, and electrochemical immunosensors have been sep-arately fabricated and tested. The fabricated microfluidic components have been surface-mounted on the microfluidic motherboard for fully integrated microfluidic biochemical detection system. A magnetic bio-bead approach has been adopted for both sampling and manipulating target biological molecules. Magnetic beads were used as both substrate of antibodies and carriers of target antigens for magnetic bead-based immunoassay, which was chosen as a proof-of-concept for the generic microfluidic bio-chemical detection system. The microfluidic and electrochemical immunosensing experiment results obtained from this work have shown that the biochemical sensing capability of the complete microfluidic subsystem is suitable for portable biochemical detection of bio-molecules. The methodology and system, which has been developed in this work, can be extended to generic bio-molecule detection and analysis systems by replacing antibody/antigen with appropriate bio receptors/reagents such as DNA fragments or oligonucleotides for application towards DNA analysis and/or high throughput protein analysis.

Microfluidic compartmentalized co-culture platform for CNS axon myelination research

This paper presents a circular microfluidic compartmentalized co-culture platform that can be used for central nervous system (CNS) axon myelination research. The microfluidic platform is composed of a soma compartment and an axon/glia compartment connected through arrays of axon-guiding microchannels. Myelin-producing glia, oligodendrocytes (OLs), placed in the axon/glia compartment, interact with only axons but not with neuronal somata confined to the soma compartment, reminiscent to in vivo situation where many axon fibres are myelinated by OLs at distance away from neuronal cell bodies. Primary forebrain neurons from embryonic day 16–18 rats were cultured inside the soma compartment for two weeks to allow them to mature and form extensive axon networks. OL progenitors, isolated from postnatal day 1-2 rat brains, were then added to the axon/glia compartment and co-cultured with neurons for an additional two weeks. The microdevice showed fluidic isolation between the two compartments and successfully isolated neuronal cell bodies and dendrites from axons growing through the arrays of axon-guiding microchannels into the axon/glia compartment. The circular co-culture device developed here showed excellent cell loading characteristics where significant numbers of cells were positioned near the axon-guiding microchannels. This significantly increased the probability of axons crossing these microchannels as demonstrated by the more than 51 % of the area of the axon/glia compartment covered with axons two weeks after cell seeding. OL progenitors co-cultured with axons inside the axon/glia compartment successfully differentiated into mature OLs. These results indicate that this device can be used as an excellent in vitro co-culture platform for studying localized axon-glia interaction and signalling.

A programmable microfluidic cell array for combinatorial drug screening

We describe the development of a fully automatic and programmable microfluidic cell culture array that integrates on-chip generation of drug concentrations and pair-wise combinations with parallel culture of cells for drug candidate screening applications. The device has 64 individually addressable cell culture chambers in which cells can be cultured and exposed either sequentially or simultaneously to 64 pair-wise concentration combinations of two drugs. For sequential exposure, a simple microfluidic diffusive mixer is used to generate different concentrations of drugs from two inputs. For generation of 64 pair-wise combinations from two drug inputs, a novel time dependent variable concentration scheme is used in conjunction with the simple diffusive mixer to generate the desired combinations without the need for complex multi-layer structures or continuous medium perfusion. The generation of drug combinations and exposure to specific cell culture chambers are controlled using a LabVIEW interface capable of automatically running a multi-day drug screening experiment. Our cell array does not require continuous perfusion for keeping cells exposed to concentration gradients, minimizing the amount of drug used per experiment, and cells cultured in the chamber are not exposed to significant shear stress continuously. The utility of this platform is demonstrated for inducing loss of viability of PC3 prostate cancer cells using combinations of either doxorubicin or mitoxantrone with TRAIL (TNF-alpha Related Apoptosis Inducing Ligand) either in a sequential or simultaneous format. Our results demonstrate that the device can capture the synergy between different sensitizer drugs and TRAIL and demonstrate the potential of the microfluidic cell array for screening and optimizing combinatorial drug treatments for cancer therapy.

A low-temperature bonding technique using spin-on fluorocarbon polymers to assemble microsystems

A new low-temperature biochemically compatible polymer bonding process has been successfully developed. The bonding has been characterized for bond strength and chemical resistance. This technique has successfully addressed a major challenge in the development of microfluidic systems from discrete components by enabling the bonding of the components to the microfluidic motherboards at low temperatures and ensuring reliable, leak-proof and chemically inert bonding. This bonding technique uses a spin-on Teflon-like amorphous fluorocarbon polymer. The bonding technique lowers the bonding temperature (~160 °C), shows a good bond strength of 4.3 MPa in silicon-to-silicon, and has excellent chemical resistance to various chemicals used in microelectromechanical systems processing.

Whole-Cell Impedance Analysis for Highly and Poorly Metastatic Cancer Cells

A micro electrical impedance spectroscopy (muEIS) system has been developed and implemented to analyze highly and poorly metastatic head and neck cancer (HNC) cell lines with single-cell resolution. The microsystem has arrays of 16 impedance analysis sites, each of which is capable of capturing a single cell and analyzing its whole-cell electrical impedance spectrum. This muEIS system was used to obtain the electrical impedance spectra of the poorly metastatic HNC cell line 686 LN and the highly metastatic HNC cell line 686 LN-M4e over a frequency range of 40 Hz - 10 MHz. The 686 LN cells had higher impedance phase compared to that of 686 LN-M4e cells at frequencies between 50 kHz and 2 MHz. This result demonstrates that the metastatic state of HNC cells can be distinguished using the developed muEIS system. This system is expected to serve as a powerful tool for future detection and quantification of cancer cells from various tumor stages.

Conjugated Oligoelectrolytes Increase Power Generation in E. coli Microbial Fuel Cells

A series of conjugated oligoelectrolytes with structural variations is used to stain E. coli. By taking advantage of a high-throughput screening platform that incorporates gold anodes, it is found that MFCs with COE-modified E. coli generate significantly higher power densities, relative to unmodified E. coli. These findings highlight the potential of using water-soluble molecules inspired by the work on organic semiconductors to improve electrode/microbe interfaces.

A microfluidic photobioreactor array demonstrating high-throughput screening for microalgal oil production†

Microalgae are envisioned as a future source of renewable oil. The feasibility of producing high-value biomolecules from microalgae is strongly dependent on developing strains with increased productivity and environmental tolerance, understanding algal gene regulation, and optimizing growth conditions for higher production of target molecules. We present a high-throughput microfluidic microalgal photobioreactor array capable of applying 64 different light conditions to arrays of microscale algal photobioreactors and apply this device to investigate how light conditions influence algal growth and oil production. Using the green colony-forming microalga Botryococcus braunii, the light intensity and light-dark cycle conditions were identified that induced 1.8-fold higher oil accumulation over the typically used culture conditions. Additionally, the studies revealed that the condition under which maximum oil production occurs is significantly different from that of maximum growth. This screening test was accomplished using the developed photobioreactor array at 250 times higher throughput compared to conventional flask-scale photobioreactors.

Air-cathode microbial fuel cell array: a device for identifying and characterizing electrochemically active microbes.

Microbial fuel cells (MFCs) have generated excitement in environmental and bioenergy communities due to their potential for coupling wastewater treatment with energy generation and powering diverse devices. The pursuit of strategies such as improving microbial cultivation practices and optimizing MFC devices has increased power generating capacities of MFCs. However, surprisingly few microbial species with electrochemical activity in MFCs have been identified because current devices do not support parallel analyses or high throughput screening. We have recently demonstrated the feasibility of using advanced microfabrication methods to fabricate an MFC microarray. Here, we extend these studies by demonstrating a microfabricated air-cathode MFC array system. The system contains 24 individual air-cathode MFCs integrated onto a single chip. The device enables the direct and parallel comparison of different microbes loaded onto the array. Environmental samples were used to validate the utility of the air-cathode MFC array system and two previously identified isolates, 7Ca (Shewanella sp.) and 3C (Arthrobacter sp.), were shown to display enhanced electrochemical activities of 2.69 mW/m(2) and 1.86 mW/m(2), respectively. Experiments using a large scale conventional air-cathode MFC validated these findings. The parallel air-cathode MFC array system demonstrated here is expected to promote and accelerate the discovery and characterization of electrochemically active microbes.