Figure 7. Images of MDA-MB-231 cancer cells from the fluorescence detection of FAM and Cy5.

The higher intensity from FAM is due to the intracellular operation of the DNAzyme motor, with each walking step restoring fluorescence of a FAM molecule. Therefore, the DNAzyme motor results in the amplified imaging of the intracellular miRNA target. The Cy5 image is much weaker because there is no amplification for the Cy5 signal. Fluorescence imaging of living cells was performed using an Olympus IX-81 microscope equipped with a Yokagawa CSU × 1 spinning disk confocal scan-head and a Hamamatsu EMCCD camera with × 40/1.3 Oil and × 20/0.85 Oil objective lenses. Two pumped diode lasers at 491 nm and 630 nm were used for the excitation of FAM and Cy5. Magnification was chosen to allow a final pixel size of 447 nm with × 20 lens and 223 nm with × 40 lens. The length of the scale bar is 17 μm.