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

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.


Related in: MedlinePlus

Closed-channel devices – A) Demountable stack-assembled flow cell (adapted from Nasse et al. [74]) to measure biological specimens with high spatial resolution. Cells are visualized through diamond films grown on silicon wafer and seals are maintained by mechanical pressure from assembled manifold. The flow cell can be disassembled after measurement to reuse parts or access cells. B) Demountable stack-assembled flow cell (adapted from Tobin et al. [73]) with machined features on separate layers. Based on a modified Bioptechs FCS3 cell, the channel and chamber layers are pressed between two CaF2 crystals for transmission measurement on a Bruker Hyperion microscope. C) Microfabrication allows more complex structures to be integrated into the flow cell and very precise control of water film thickness to be maintained uniformly over the entire measurement area. Device shown from Grenci et al. [87] has channels defined in a photosensitive polymer that covers the CaF2 window. The device is permanently sealed by thermomechanical bonding.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4997923&req=5

Figure 3: Closed-channel devices – A) Demountable stack-assembled flow cell (adapted from Nasse et al. [74]) to measure biological specimens with high spatial resolution. Cells are visualized through diamond films grown on silicon wafer and seals are maintained by mechanical pressure from assembled manifold. The flow cell can be disassembled after measurement to reuse parts or access cells. B) Demountable stack-assembled flow cell (adapted from Tobin et al. [73]) with machined features on separate layers. Based on a modified Bioptechs FCS3 cell, the channel and chamber layers are pressed between two CaF2 crystals for transmission measurement on a Bruker Hyperion microscope. C) Microfabrication allows more complex structures to be integrated into the flow cell and very precise control of water film thickness to be maintained uniformly over the entire measurement area. Device shown from Grenci et al. [87] has channels defined in a photosensitive polymer that covers the CaF2 window. The device is permanently sealed by thermomechanical bonding.

Mentions: Liquid flow cells (Figure 3) represent the foundation of the microfluidic closed-channel devices that comprise the majority of devices in use at various synchrotron facilities today. First employed by Wieliczka et al. [67] in 1989 to measure the absorption coefficients of water, their basic structure is a micron-scale thick gasket pressed between two infrared crystals and mechanically assembled as a stack in an external manifold that may also allow for sample injection and temperature control. This configuration is generally used for transmission experiments and allows for a sample to be maintained in relatively uniform, thin layer of water with absorption signal below saturation so that the water background can be subtracted later to obtain the sample spectra [66, 68-70]. This scheme is versatile in that a variety of different windows may be used and it is typically demountable, so that flow cells can be disassembled for cleaning and reuse. The main drawback of demountable flow cells is that the path length, which relies on mechanical pressure, is not easily reproducible between measurements, increasing bias when comparing data from different experiments. Poor sealing, leakage, and limited experimental complexity are two additional shortcomings when it is compared to approaches that use microfabrication.


Microfluidic Approaches to Synchrotron Radiation-Based Fourier Transform Infrared (SR-FTIR) Spectral Microscopy of Living Biosystems
Closed-channel devices – A) Demountable stack-assembled flow cell (adapted from Nasse et al. [74]) to measure biological specimens with high spatial resolution. Cells are visualized through diamond films grown on silicon wafer and seals are maintained by mechanical pressure from assembled manifold. The flow cell can be disassembled after measurement to reuse parts or access cells. B) Demountable stack-assembled flow cell (adapted from Tobin et al. [73]) with machined features on separate layers. Based on a modified Bioptechs FCS3 cell, the channel and chamber layers are pressed between two CaF2 crystals for transmission measurement on a Bruker Hyperion microscope. C) Microfabrication allows more complex structures to be integrated into the flow cell and very precise control of water film thickness to be maintained uniformly over the entire measurement area. Device shown from Grenci et al. [87] has channels defined in a photosensitive polymer that covers the CaF2 window. The device is permanently sealed by thermomechanical bonding.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 3: Closed-channel devices – A) Demountable stack-assembled flow cell (adapted from Nasse et al. [74]) to measure biological specimens with high spatial resolution. Cells are visualized through diamond films grown on silicon wafer and seals are maintained by mechanical pressure from assembled manifold. The flow cell can be disassembled after measurement to reuse parts or access cells. B) Demountable stack-assembled flow cell (adapted from Tobin et al. [73]) with machined features on separate layers. Based on a modified Bioptechs FCS3 cell, the channel and chamber layers are pressed between two CaF2 crystals for transmission measurement on a Bruker Hyperion microscope. C) Microfabrication allows more complex structures to be integrated into the flow cell and very precise control of water film thickness to be maintained uniformly over the entire measurement area. Device shown from Grenci et al. [87] has channels defined in a photosensitive polymer that covers the CaF2 window. The device is permanently sealed by thermomechanical bonding.
Mentions: Liquid flow cells (Figure 3) represent the foundation of the microfluidic closed-channel devices that comprise the majority of devices in use at various synchrotron facilities today. First employed by Wieliczka et al. [67] in 1989 to measure the absorption coefficients of water, their basic structure is a micron-scale thick gasket pressed between two infrared crystals and mechanically assembled as a stack in an external manifold that may also allow for sample injection and temperature control. This configuration is generally used for transmission experiments and allows for a sample to be maintained in relatively uniform, thin layer of water with absorption signal below saturation so that the water background can be subtracted later to obtain the sample spectra [66, 68-70]. This scheme is versatile in that a variety of different windows may be used and it is typically demountable, so that flow cells can be disassembled for cleaning and reuse. The main drawback of demountable flow cells is that the path length, which relies on mechanical pressure, is not easily reproducible between measurements, increasing bias when comparing data from different experiments. Poor sealing, leakage, and limited experimental complexity are two additional shortcomings when it is compared to approaches that use microfabrication.

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.


Related in: MedlinePlus