Label-Free Live Cell Imaging
Most biological studies involve cell research. Living cell imaging, whether observed with the naked eye by camera or microscope, has become one of the most important parts in biological research. One of the tools for imaging living cells with high sensitivity and specificity is fluorescence microscope. Due to the small number of endogenous fluorescent molecules, probes and antibodies labeled with fluorescent labels can reveal the location of specific molecules in cells. However, one of the main disadvantages of fluorescence imaging is that due to the complexity of intracellular biological processes, the impact of added fluorescent labels on biological systems is often difficult to predict. Therefore, the ideal imaging tool for cell research is a tool with high specificity and sensitivity, but does not need labeling, and can be applied to live cell imaging.
Figure 1．The nucleolus of a live HeLa cell imaged by label-free optical diffraction tomography (ODT) (Kim, et al., 2019).
Label-free live cell imaging does not add exogenous reagents that may interfere with the physiological response under study and does not need to treat the cells with fixatives, which is a cell-killing process. This imaging technique has been used by scientists for the better understanding of cell dynamics and biological functions. CD BioSciences can provide you with comprehensive services based on label-free live cell imaging technology. If you have any needs, please feel free to contact us.
Label-Free Live Cell Imaging
Phase contrast (PC) and differential interference contrast (DIC) microscopy are the most popular label-free imaging techniques in biological research. Both technologies use specific optical devices to convert the phase difference caused by cell and intracellular characteristics into the change of lightwave amplitude. Unlike phase changes, these changes can be detected by the human eye or recorded as pixel intensity changes on the camera (Fig. 2). However, the intensity in PC and DIC images is not the quantification of phase delay. Low image contrast will make automatic image segmentation difficult under high cell density.
Figure 2．Use of phase to create image contrast (Kasprowicz, et al., 2017).
Quantitative phase imaging is label-free, which provides higher content and contrast than traditional technology. High contrast images help to generate single-cell indicators through more robust segmentation and tracking, to form an unlabeled dynamic phenotype describing intercellular heterogeneity and temporal changes. Compared with the average value at the population level, the dynamic phenotype at the individual cell level has a greater ability to distinguish the cell response to treatment, which is clinically relevant, such as in cancer treatment. In addition, since the data obtained are unlabeled, the same cells can be used for further analysis or expansion, which has potential benefits in the field of regenerative and personalized medicine.
Comparison Between Label-Free and Fluorescence Live-Cell Imaging Techniques
|Label-Free live-cell imaging
|Fluorescence live-cell imaging
|Study cellular dynamics & cell morphology
|Study cellular processes and functions. Visualise specific structures and proteins.
|Can be very time consuming
|Can be very expensive
|Non-invasive. Cells unperturbed and in their natural state
|Invasive labeling-techniques and phototoxicity
|Can analyze cells over long periods of time
|Shorter periods of analysis due to phototoxicity
Applications of Label-Free Live Cell Imaging
- Measuring the growth and proliferation of cells at the individual cell level and population level
- Imaging the cell population can evaluate the heterogeneity between cells to yield results of clinical importance
- Obtaining information about the motor behavior of individual cells
- Information on cell cycle and lineage can be obtained and used to develop anti-mitotic cancer drugs
- Counting cells without cell staining
- Kim, Tae-Keun, et al. "Physicochemical properties of nucleoli in live cells analyzed by label-free optical diffraction tomography." Cells 8.7 (2019): 699.
- Kasprowicz, Richard, Rakesh Suman, and Peter O'Toole. "Characterising live cell behaviour: Traditional label-free and quantitative phase imaging approaches." The international journal of biochemistry & cell biology 84 (2017): 89-95.
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