The use of longer wavelengths should help improve the surgical outcome in ultrashort pulse laser surgery of the cornea when working on pathological tissue. A wavelength of approximately 1650 nm appears to be a good compromise, as it allows for reduced light scattering while keeping optical absorption reasonably low.
We demonstrate that a live epithelial cell monolayer can act as a planar waveguide. Our infrared reflectivity measurements show that highly differentiated simple epithelial cells, which maintain tight intercellular connectivity, support efficient waveguiding of the infrared light in the spectral region of 1.4–2.5 µm and 3.5–4 µm. The wavelength and the magnitude of the waveguide mode resonances disclose quantitative dynamic information on cell height and cell-cell connectivity. To demonstrate this we show two experiments. In the first one we trace in real-time the kinetics of the disruption of cell-cell contacts induced by calcium depletion. In the second one we show that cell treatment with the PI3-kinase inhibitor LY294002 results in a progressive decrease in cell height without affecting intercellular connectivity. Our data suggest that infrared waveguide spectroscopy can be used as a novel bio-sensing approach for studying the morphology of epithelial cell sheets in real-time, label-free manner and with high spatial-temporal resolution.
We report a spectroscopic technique that combines the Fourier-Transform Infrared Spectroscopy with the Surface Plasmon Resonance. This tool enables sensitive infrared spectroscopy of liquid and solid objects in the attenuated total reflectance mode. The FTIR-SPR technique is similar to FTIR-ATR technique but has higher sensitivity due to resonance amplification of the surface electric field. The label-free FTIR-SPR technique is especially advantageous for living cell studies since it combines spectroscopic information inherent to FTIR with structural information provided by the Surface Plasmon Resonance. We discuss the FTIR-SPR technique for label-free studies of cell sedimentation and spreading on substrate and for surface plasmon spectroscopy.PACS 05. 52.35.Mw, 96.50.Fm.
The cell morphology is a valuable indicator of the physical condition and general status of the cell. Here we demonstrate a methodology for noninvasive biosensing of adherent living cells. Our method is based on infrared reflection spectroscopy of living cells cultured on thin Au film. To characterize cell morphology we utilized the unique properties of the infrared surface plasmon (λ=1-3 μm) and infrared guided wave that travel inside the cell monolayer. We demonstrate that our method enables monitoring of submicron variations in cell morphology in real-time and in a labelfree manner. In addition to morphological characterization, our method allows investigation of chemical composition and molecular structure of cells through infrared absorption spectroscopy analysis.
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