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Microfluidic Approaches to Synchrotron Radiation-Based Fourier Transform Infrared (SR-FTIR) Spectral Microscopy of Living Biosystems

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ABSTRACT

A long-standing desire in biological and biomedical sciences is to be able to probe cellular chemistry as biological processes are happening inside living cells. Synchrotron radiation-based Fourier transform infrared (SR-FTIR) spectral microscopy is a label-free and nondestructive analytical technique that can provide spatiotemporal distributions and relative abundances of biomolecules of a specimen by their characteristic vibrational modes. Despite great progress in recent years, SR-FTIR imaging of living biological systems remains challenging because of the demanding requirements on environmental control and strong infrared absorption of water. To meet this challenge, microfluidic devices have emerged as a method to control the water thickness while providing a hospitable environment to measure cellular processes and responses over many hours or days. This paper will provide an overview of microfluidic device development for SR-FTIR imaging of living biological systems, provide contrast between the various techniques including closed and open-channel designs, and discuss future directions of development within this area. Even as the fundamental science and technological demonstrations develop, other ongoing issues must be addressed; for example, choosing applications whose experimental requirements closely match device capabilities, and developing strategies to efficiently complete the cycle of development. These will require imagination, ingenuity and collaboration.

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Open-channel devices – A) Open-channel device to study live bacteria in aqueous environments (adapted from Holman et al. [96]). The device is composed of channels etched into a silicon wafer. Flow of media is maintained in channels by hydrophobic treatment to non-channel surfaces and liquid flow is controlled by hydrostatic pressure in a feeder droplet. B) Membrane device to study cells that grow at the liquid air interface (adapted from Loutherback et al. [97]). The cells are maintained in a thin layer of water on top of a gold-coated porous membrane. Constant flow of media underneath the membrane allows for nutrients to be replenished by capillary action.
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Figure 4: Open-channel devices – A) Open-channel device to study live bacteria in aqueous environments (adapted from Holman et al. [96]). The device is composed of channels etched into a silicon wafer. Flow of media is maintained in channels by hydrophobic treatment to non-channel surfaces and liquid flow is controlled by hydrostatic pressure in a feeder droplet. B) Membrane device to study cells that grow at the liquid air interface (adapted from Loutherback et al. [97]). The cells are maintained in a thin layer of water on top of a gold-coated porous membrane. Constant flow of media underneath the membrane allows for nutrients to be replenished by capillary action.

Mentions: A relatively new approach in microfluidic devices for live cell imaging is the application of open-channel devices (Figure 4). These are characterized by having one surface of the fluid exposed to atmosphere and the liquid thickness controlled by surface effects. In 2009, Holman et al. [96] used continuous flow of fluid through a microchannel etched in silicon, supplied by a combination of hydrostatic pressure and capillary forces. Hydrophobic treatment to other surfaces ensures water flows exclusively within the channel and forces were carefully balanced between the hydrostatic pressure of a feeder droplet, and capillary pull into a cleanroom tissue to maintain constant fluid thickness. This method was used to track the development and growth of an E. Coli biofilm over the course of two days using transmission measurement.


Microfluidic Approaches to Synchrotron Radiation-Based Fourier Transform Infrared (SR-FTIR) Spectral Microscopy of Living Biosystems
Open-channel devices – A) Open-channel device to study live bacteria in aqueous environments (adapted from Holman et al. [96]). The device is composed of channels etched into a silicon wafer. Flow of media is maintained in channels by hydrophobic treatment to non-channel surfaces and liquid flow is controlled by hydrostatic pressure in a feeder droplet. B) Membrane device to study cells that grow at the liquid air interface (adapted from Loutherback et al. [97]). The cells are maintained in a thin layer of water on top of a gold-coated porous membrane. Constant flow of media underneath the membrane allows for nutrients to be replenished by capillary action.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4997923&req=5

Figure 4: Open-channel devices – A) Open-channel device to study live bacteria in aqueous environments (adapted from Holman et al. [96]). The device is composed of channels etched into a silicon wafer. Flow of media is maintained in channels by hydrophobic treatment to non-channel surfaces and liquid flow is controlled by hydrostatic pressure in a feeder droplet. B) Membrane device to study cells that grow at the liquid air interface (adapted from Loutherback et al. [97]). The cells are maintained in a thin layer of water on top of a gold-coated porous membrane. Constant flow of media underneath the membrane allows for nutrients to be replenished by capillary action.
Mentions: A relatively new approach in microfluidic devices for live cell imaging is the application of open-channel devices (Figure 4). These are characterized by having one surface of the fluid exposed to atmosphere and the liquid thickness controlled by surface effects. In 2009, Holman et al. [96] used continuous flow of fluid through a microchannel etched in silicon, supplied by a combination of hydrostatic pressure and capillary forces. Hydrophobic treatment to other surfaces ensures water flows exclusively within the channel and forces were carefully balanced between the hydrostatic pressure of a feeder droplet, and capillary pull into a cleanroom tissue to maintain constant fluid thickness. This method was used to track the development and growth of an E. Coli biofilm over the course of two days using transmission measurement.

View Article: PubMed Central - PubMed

ABSTRACT

A long-standing desire in biological and biomedical sciences is to be able to probe cellular chemistry as biological processes are happening inside living cells. Synchrotron radiation-based Fourier transform infrared (SR-FTIR) spectral microscopy is a label-free and nondestructive analytical technique that can provide spatiotemporal distributions and relative abundances of biomolecules of a specimen by their characteristic vibrational modes. Despite great progress in recent years, SR-FTIR imaging of living biological systems remains challenging because of the demanding requirements on environmental control and strong infrared absorption of water. To meet this challenge, microfluidic devices have emerged as a method to control the water thickness while providing a hospitable environment to measure cellular processes and responses over many hours or days. This paper will provide an overview of microfluidic device development for SR-FTIR imaging of living biological systems, provide contrast between the various techniques including closed and open-channel designs, and discuss future directions of development within this area. Even as the fundamental science and technological demonstrations develop, other ongoing issues must be addressed; for example, choosing applications whose experimental requirements closely match device capabilities, and developing strategies to efficiently complete the cycle of development. These will require imagination, ingenuity and collaboration.

No MeSH data available.