|
Live-cell mid-infrared (MIR) imaging has always been challenging because of the absorptive nature of water. However, there is a strong drive to image this spectroscopic window–to see the protein and lipid vibrations directly without the help of dyes. Though the dyes are convenient for imaging, they interfere with the biological functions of live cells. In the past two decades, people have relied on attenuated total reflectance (ATR) Fourier transform infrared (FTIR) spectroscopic imaging to probe such systems to reduce the infrared penetration depth to a few microns. In our previous works, we found a way to further restrict the penetration to a hundred nanometers with plasmonic nanoantennas, also known as the metasurfaces. We named the technique-metasurface-enhanced infrared reflection spectroscopy (MEIRS), and used it for either label-free spectroscopy or imaging. We had demonstrated MEIRS in various live-cell drug dynamics studies, including trypsin, cholesterol depleting agents, and chemotherapeutics, of live cells enclosed in microfluidics chambers. With the recent advancement of commercial mid-infrared quantum cascade laser (QCL), we now have a unique opportunity to acquire high-quality single-cell resolution metasurface-enhanced infrared reflection chemical imaging (MIRCI), which reveals the important protein information in real time. We built an inverted QCL microscope setup and cultured the cells on a cell-culture multiwell plate. The bottom of the multiwells is made of infrared-transparent window and with metasurface fabricated on. In this work, we demonstrated two proofs of concept of MIRCI on both fixed cells in water (single-cell resolution and spectroscopy) and live cells (capturing cell adhesion process). The application provides a novel tool to the drug discovery and fundamental cell biology research.
|
