The promise of DNA nanomachines that can change shape due to specific triggers, and in such a way create complicated systems, is not a new notion. In the latest edition of Nature Nanotechnology, Indian scientists are reporting the development of an interesting DNA pH sensor, a DNA nanomachine that “maps spatial and temporal pH changes inside living cells.”
"We named our DNA nanomachine the I-switch" Yamuna Krishnan tells Nanowerk. "The device is externally triggered by protons and functions as a pH sensor based on fluorescence resonance energy transfer (FRET) inside living cells. We demonstrate the ability of this DNA nanomachine to function inside living cells by using it to map spatio-temporal pH changes associated with endosome maturation. Our studies show that it is able to function as efficiently inside the endosome of a living cell as it does in a test tube."
Krishnan is a scientist at the National Centre for Biological Sciences in Bangalore, India, where she heads the Chemical Biology Group. The DNA assembly developed by her team is a robust pH-triggered nanoswitch with reasonably fast response times, sustained efficiency over several cycles, and a working cycle that does not generate toxic byproducts (the byproducts of a complete cycle for the I-switch are salt and water).
The I-switch has a pH sensitivity between pH 5.5 and 6.8 – which is ideal for monitoring changes in intracellular pH – and offers complementary information to that obtained through the use of small-molecule fluorescent pH probes. Krishnan points out that, unlike such pH probes, the I-switch is a FRET-based sensor that is equally bright at both physiological and acidic values of pH.
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Abstract: A DNA nanomachine that maps spatial and temporal pH changes inside living cells
Image: Drosophila cells with the I-switch inside their endosomes. (Image: Dr. Krishnan, National Centre for Biological Sciences)