New label-free microscope enables dynamic, high-res imaging of cell interactions
University of Illinois Electrical & Computer Engineering and Bioengineering Professor Brian Cunningham’s Nano Sensors group has invented a novel live-cell imaging method that could someday help biologists better understand how stem cells transform into specialized cells and how diseases like cancer spread. Their Photonic Crystal Enhanced Microscope (PCEM) is capable of monitoring and quantitatively measuring cell adhesion, a critical process involved cell migration, cell differentiation, cell division, and cell death.Micro + Nanotechnology Lab.
Most conventional imaging methods rely on fluorescent dyes, which attach to and illuminate the cell components so they are visible under a microscope. However, fluorescent tagging has its limitations—namely that it is invasive, difficult for quantitative measurement, and only provides a short-term window of time for cell examination and measurement due to photobleaching.
According to PCEM lead researcher Yue Zhuo, a post-doctoral Beckman Institute Fellow, fluorescent tagging doesn’t allow scientists to see how a protein or cell changes over time. “You can see the cell for maybe a few hours maximum before the fluorescent light dies out, but it takes several days to conduct a stem cell experiment,” said Zhuo. “Scientists commonly use fluorescent tagging because there’s no better way to monitor live cells due to their low imaging contrast among cellular organelles. That urges us to develop a label-free and high-resolution imaging method for live cell study.”
In Zhuo’s apparatus, the photonic crystal biosensor is an optical sensor which can apply to any attachable cells. The sensor surface is coated with extracellular matrix materials to facilitate cellular interactions, which are then viewed through a normal objective lens and recorded with a CCD camera.
“The advantage of our PCEM system is you can see as the [live] cell is beginning to attach to our sensor, and we can quantitatively and dynamically measure what happened at that time,” Zhuo said. “We’re able to actually measure a very thin layer on the bottom of the cell that’s about 100 nanometers, which is beyond the diffraction limit for visible light.”
By using the PCEM, Zhuo has successfully measured the effective mass density of cell membranes during stem cell differentiation, and cancer cell response to drugs in an extended period. She reports her results in the November 2016 (Volume 50), issue of Progress in Quantum Electronics, “Quantitative imaging of cell membrane-associated effective mass density using Photonic Crystal Enhanced Microscopy.”
This project was funded by grants from the National Science Foundation and National Institutes of Health. Fellow research collaborators include: University of Illinois Chemical and Biomolecular Engineering Associate Professor Brendan Harley and post-doctoral researcher Ji Sun Choi; and Electrical & Computer Engineering graduate student Hojeong Yu.
For more information, contact:
• Professor Brian Cunningham at 217.265.6291; firstname.lastname@example.org
• Yue Zhuo at email@example.com