Micro total analysis systems for cell biology and biochemical assays.

Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, United States.
Analytical Chemistry (Impact Factor: 5.83). 10/2011; 84(2):516-40. DOI: 10.1021/ac202611x
Source: PubMed

ABSTRACT Novel applications of micro total analysis systems (μTAS) are addressing fundamental biological questions, fabricating new biomedical reagents, and developing cell and biochemical assays. These efforts impact progress in all areas of μTAS from materials to fluidic handling as well as detection and external control systems. Three areas show the greatest current and potential impact on the biomedical sciences: improvements in device fabrication and operation, development of enabling technologies, and advancements at the interface with biology (Figure 1). The range of materials from which devices can be fabricated has expanded considerably and now includes paper, fabric and thread, and a multitude of polymers as well as more conventional materials. Thus device substrates and component materials suitable for nearly all biological applications are readily available. Devices are also becoming increasingly integrated with advancements in sampling handling and preparation, a key and first step in any biological analysis. Another growing area focuses on modular components that can be mixed and matched on-demand and applied to many different assays, so-called programmable microfluidics. This development should enhance the rate at which new bioassays are generated as well as customize existing experimental protocols. A second area of rapid advancement has been the development new technologies that enable assays that cannot be efficiently performed by any method except μTAS. Novel analyses of single cells are enabled due to effective manipulation of picoliter-scale volumes. Synthesis and screening of large-scale libraries has become increasingly feasible due to the fast processing speeds and combinatorial mixing of reagents provided by lab-on-chip systems. Increased automation within a completely contained system has now begun to provide some of the first true μTAS diagnostic devices for clinical medicine. The third area in which μTAS has begun to yield high dividends is the interfacing of living entities with microdevices to create biological communities including tissues and organs on-chip. Control of cell placement in multiple dimensions has produced biological systems midway between the conventional tissue-culture dish and an intact animal. Thus the complexities of living constructs can be recreated in a controlled experimental environment permitting groundbreaking biological questions to be addressed. Application of μTAS in all of these areas continues to be highly interdisciplinary, utilizing techniques and strategies from almost every scientific field. This multidisciplinary focus insures continued relevance to the biological community as well as a bright future.

1 Bookmark
  • [Show abstract] [Hide abstract]
    ABSTRACT: A number of recent studies have exploited the sizes and functional properties of microdevices and cellular mechanical components to construct bio-microactuators. We previously developed bio-micropumps powered by cardiomyocytes that utilizes glucose in the medium as chemical energy. To fabricate the pump, however, primary neonatal rat cardiomyocytes are indispensable. The operation of harvesting primary cells is inconvenient and ethically not adequate due to the need for animals sacrifice. In contrast, induced pluripotent stem (iPS) cells are obtained from subcutaneous tissue. Their most significant properties are that they proliferate indefinitely and can be differentiated into many kinds of cells, including cardiomyocytes, and also have no ethical issue differently from ES cells. By exploiting these properties of iPS cells, the above issues will be addressed. Based on this concept, we constructed a system for driving fluids as a principal component of a micropump by differentiating iPS cells into spontaneously beating cardiomyocytes. Cellular contractile force was transmitted to fluid in a microchannel by a tent-like thin membrane. The microchip was irradiated with O2 plasma and coated with gelatin to attach the cells. Embryoid bodies (EBs) of mouse-derived iPS cells were seeded on the microchip and incubated at 37 °C without Leukemia Inhibitory Factor (LIF) to differentiate them into cardiomyocytes. About 2 weeks later, EB beating and periodical oscillation of fluid in a microchannel connected to a diaphragm chamber was observed. The theoretical flow rate assuming the use of ideal check valves (Q) was 6.9 nL/min. Our device presents a reasonable alternative to normal cardiomyocytes for preliminary investigations requiring bio-actuating pumps.
    Sensors and Actuators B Chemical 04/2015; 210. · 3.84 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Rational development of more physiologic in vitro models includes the design of robust and flexible 3D-microtissue-based multi-tissue devices, which allow for tissue-tissue interactions. The developed device consists of multiple microchambers interconnected by microchannels. Pre-formed spherical microtissues are loaded into the microchambers and cultured under continuous perfusion. Gravity-driven flow is generated from on-chip reservoirs through automated chip-tilting without any need for additional tubing and external pumps. This tilting concept allows for operating up to 48 devices in parallel in order to test various drug concentrations with a sufficient number of replicates. For a proof of concept, rat liver and colorectal tumor microtissues were interconnected on the chip and cultured during 8 days in the presence of the pro-drug cyclophosphamide. Cyclophosphamide has a significant impact on tumor growth but only after bio-activation by the liver. This effect was only observed in the perfused and interconnected co-cultures of different microtissue types on-chip, whereas the discontinuous transfer of supernatant via pipetting from static liver microtissues that have been treated with cyclophosphamide did not significantly affect tumor growth. The results indicate the utility and multi-tissue functionality of this platform. The importance of continuous medium circulation and tissue interaction is highlighted.
    Journal of Biotechnology 01/2015; · 2.88 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this work, autonomously functioning artificial ion channels were fabricated and assessed. An electrowetting-based valve was formed in a constricted region surrounded by poly(dimethylsiloxane) walls with a gold electrode at the base. The gold electrode was connected to an integrated hydrogen electrode to detect the pH of a solution to be transported. A mixed potential was generated when the gold valve electrode and a platinum black electrode in the hydrogen electrode were connected by the solution, which polarized the gold electrode. As a result, the gold electrode became sufficiently hydrophilic at pH values above a certain threshold, and the solution was able to pass through the valve region. The threshold potential could be adjusted by changing the width of the valve. To expand the range of application to biomolecules, a urea-responsive valve was also fabricated by immobilizing the enzyme urease on the platinum black electrode. Moreover, passage of the solution through the valve was coupled with the transportation of a second solution through a separate flow channel, using a composite electrode consisting of a gold electrode used to form the electrowetting-based valve and a zinc electrode to detect the arrival of a solution.
    Sensors and Actuators B Chemical 02/2013; 177:929-935. · 3.84 Impact Factor

Full-text (2 Sources)

Available from
May 26, 2014