Metasurfaces for cell capturing and infrared spectroscopy
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Metasurfaces, a 2-dimensional subclass of metamaterials, have attracted attention due to the ability to fabricate thin devices with extraordinary properties. High localized field enhancement of mid-infrared (IR) Fano resonant metasurfaces makes them an appealing platform for sensing of biological materials. Metasurface-enhanced infrared spectroscopy (MEIRS) has been used in this work to study mid-IR spectra of human cells, a methodology known as spectral cytopathology. Various characteristic vibrational modes of cells are recognized using MEIRS of fixed and live cells. Fixed normal and cancerous colon cells are distinguished by their mid-IR spectra using principal component analysis (PCA). A microfluidic device is proposed and constructed for capturing and spectral analysis of live cells. Dielectrophoresis (DEP) is used to capture cells in aqueous solution directly onto metasurfaces for their interrogation with MEIRS. It is shown that live cell spectra can be collected within a few minutes. DEP captured epithelial cancer cells and lymphocytes are distinguished by their spectra using PCA. Furthermore, it is demonstrated that only epithelial cells can be captured on the metasurfaces using DEP, while preventing blood cells from being collected. This opens the possibility to use such a device for selective capturing of circulating tumor cells from blood samples for immediate spectral characterization.