Development of simultaneous measurement of micro/macro-molecular kinetics in a living cell by laser speckle microscopy

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A laser speckle microscopy imaging system for observation of living cells was developed. This system consists of an optical microscope, a laser source, and a video camera. The system has an advantage in that cellular conditions could be instantaneously determined by observing speckle movements without any special preparation such as staining and genetic manipulation. In the experiments, the speckle fluctuations of living and fixed HeLa cells were compared with the change in the temperature of the culture medium around the cells, and their video images were quantitatively analyzed. Laser speckle fluctuations on these cells were also analyzed by using frequency spectra of speckle fluctuations. In this frequency analysis, particular peak around a few Hz was observed in a living cell. It was also found in this study that by using a femto second laser illumination, simultaneous observation of auto-fluorescence from bio-molecules and laser speckle in a living cell could be possible in this laser speckle microscopic system. By applying this system, it is possible to estimate not only cellular activity but also real-time movements of intercellular materials including the cytoplasm without requiring complicated labeling processes.