Metasurface-enhanced infrared spectroscopy for continuously monitoring the effect of cholesterol depletion in live cells

摘要

Surface-enhanced infrared absorption (SEIRA) based on top-down fabricated nanostructures such as nanoantennas andmetasurfaces has attracted much attention in recent years. These plasmonic resonant nanostructures can enhance the IRabsorption signal of nearby molecules through its nearfield enhancement and have been shown to be able to detectadsorbed monolayers of proteins and lipids through their IR absorption spectra. Here, we demonstrate the continuousmonitoring of cellular responses to stimuli using metasurface-enhanced infrared spectroscopy (MEIRS). A431 cells areseeded on a gold plasmonic metasurface fabricated on CaF_2 substrate. Continuous monitoring is made possible byintegrating the metasurface with a flow chamber, and the IR absorption spectra of the attached cells are measured inreflectance mode under continuous perfusion of cell culture medium. Scanning electron microscopy (SEM) revealed thatthe cells preferentially adhere to gold surfaces rather than CaF_2 surfaces, suggesting that the IR signal measured throughMEIRS is highly sensitive to the cells’ attachment and interaction with the gold metasurface. We have monitored theeffect of methyl-beta-cyclodextrin, a cholesterol-depleting compound, on A431 cells. Principal component analysishighlighted the complex and subtle spectral changes of the cells.