Transmission Fourier Transform Infrared (FT-IR) imaging, mapping, and synchrotron scanning microscopy with ZnS hemispheres on living mammalian cells at sub-cellular resolution

DOI: 10.1177/0003702819898275

Authors: Ka Lung Andrew Chan (King's College London) , Ali Altharawi (King's College London) , Pedro L. Fale (University of Lisbon) , Cai Li Song (Imperial College London) , Sergei G. Kazarian (Imperial College London) , Gianfelice Cinque (Diamond Light Source) , Valerie Untereiner (University of Reims Champagne-Ardenne) , Ganesh Sockalingum (University of Reims Champagne-Ardenne)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Applied Spectroscopy

State: Published (Approved)
Published: February 2020
Diamond Proposal Number(s): 17501

Abstract: Fourier transform infrared (FT-IR) spectroscopic imaging and microscopy of single living cells are established label-free technique for the study of cell biology. The constant driver to improve the spatial resolution of the technique is due to the diffraction limit given by IR wavelength making subcellular study challenging. Recently we have reported, with the use of a prototype ZnS transmission cell made of two hemispheres, that the spatial resolution is improved by the factor of the refractive index of ZnS, achieving a λ/2.7 spatial resolution using the synchrotron– IR microscopy with a 36x objective with numerical aperture (NA) of 0.5. To refine and to demonstrate that the ZnS hemisphere transmission device can be translated to standard bench-top FT-IR imaging systems, we have, in this work, modified the device to achieve a more precise path length, which has improved the spectral quality of the living cells, and showed for the first time that the device can be applied to study live cells with three different bench-top FT-IR imaging systems. We applied focal plane array (FPA) imaging, linear array, and a synchrotron single point scanning method and demonstrated that in all cases, subcellular details of individual living cells can be obtained. Results have shown that imaging with the FPA detector can measure the largest area in a given time whilst measurements from the scanning methods produced a smoother image. Synchrotron single point mapping produced the best quality image and has the flexibility to introduce over sampling to produce images of cells with great details, but it is time consuming in scanning mode. In summary, this work has demonstrated that the ZnS hemispheres can be applied in all three spectroscopic approaches to improve the spatial resolution without any modification to the existing microscopes.

Journal Keywords: Fourier transform infrared imaging; FT-IR imaging; live cell; subcellular; nucleus; lipid; label-free; ZnS hemispheres spatial resolution

Subject Areas: Technique Development, Biology and Bio-materials


Instruments: B22-Multimode InfraRed imaging And Microspectroscopy