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    Item type:Publication, Access status: without files ,
    Elastic reversible valves on centrifugal microfluidic platforms
    (2019-03-21)
    Aeinehvand, Mohammad Mahdi
    ;
    Weber, Laura
    ;
    Jiménez, Martín
    ;
    Ibrahim, Fatimah
    ;
    Palermo, Andrea
    Reversible valves on centrifugal microfluidic platforms facilitate the automation of bioanalytical assays, especially of those requiring a series of steps (such as incubation) in a single reaction chamber. In this study, we present fixed elastic reversible (FER) valves and tunable elastic reversible (TER) valves that are easy to fabricate, implement and control. In the FER valve the compression of an elastic barrier/patch against a microchamber's outlet prevents the release of liquid. The valve sealing pressure was determined by adjusting the engraving depth of the valve-seat at which the elastic patch was located, this allows to set the sealing pressure during disc fabrication. In the TER valve, the patch compression value and sealing pressure is controlled by the penetration depth of a plastic screw into the valve-seat. The ER valves prevent liquid flow until the centrifugal force overcomes their sealing pressure. Moreover, at a constant spin speed, turning the screw of a TER valve reduces its sealing pressure and opens the valve. Therefore, the TER valve allows for controlling of the liquid transfer volume at various spin speeds. The FER and TER valves' behavior is mathematically described and equations for the prediction of their operation under centrifugal forces are provided. As a point-of-care (POC) application of ER valves, we have developed a microfluidic disc with a series of TER valves and peptide microarrays for automated multiplexed detection of five different proteins from a single serum sample.
    Publicationtype: Journal Article
      4
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    Item type:Publication, Access status: without files ,
    A microfluidic device for immuno-affinity-based separation of mitochondria from cell culture
    (Royal Society of Chemistry (RSC), 2013-08-19)
    Kayo, Sabrina
    ;
    Bahnemann, Janina Stephanie
    ;
    Klauser, Matthias
    ;
    Pörtner, Ralf
    ;
    Zeng, An-Ping
    In this work, we present a method to isolate mitochondria of mammalian cells after cell disruption on microscale. The device is composed of linear microchannels cast in PDMS (polydimethylsiloxane). Specific antibodies against the translocase outer membrane protein of the mitochondria are immobilized on the surface of the substrate using an avidin-biotin sandwich construct. The mitochondria can be captured in the channel, whereas the remains of the cell lysate flow out the chip unhindered. The captured mitochondria can be observed directly on chip. A successful immobilization of pre-isolated mitochondria was shown at a flow rate between 0 and 5 μl min-1 (≈0-2.5 mm s -1). After fluorescence staining, we demonstrated that the mitochondria covered around 3% of the channel surface. The mitochondria appeared in a distinct spherical shape with a diameter of around 0.8-1.2 μm. Further validation of the microfluidic device using non-treated cell lysate was done at 2 μl min-1. The immobilized mitochondria were smaller with a diameter of around ≈490 nm. We observed a surface coverage of around 4%. The immobilized mitochondria were active and stable for over 2 h without cooling and were shown to be able to produce ATP under stage 3 respiration on chip. © 2013 The Royal Society of Chemistry.
    Publicationtype: Journal Article
      54