Single walled carbon nanotubes wrapped with DNA can be placed inside living cells and detect trace amounts of harmful contaminants, report researchers at the University of Illinois at Urbana-Champaign.

Their discovery opens the door to new types of optical sensors and biomarkers that exploit the unique properties of nanoparticles in living systems.

“We found that the thermodynamics that drive the switching back and forth between these two forms of DNA structure would modulate the electronic structure and optical emission of the carbon nanotube,” said Michael Strano, a professor of chemical and biomolecular engineering at University of Illinois at Urbana-Champaign.

When the DNA is exposed to ions of certain atoms — such as calcium, mercury and sodium — the negative charges become neutralized and the DNA changes shape in a manner similar to its natural shape-shift from the B form to Z form. This reduces the surface area covered by the DNA, perturbing the electronic structure and shifting the nanotube’s natural, near-infrared fluorescence to a lower energy level. The change in emission energy indicates how many ions bind to the DNA.

References:

Daniel A. Heller et al., “Optical Detection of DNA Conformational Polymorphism on Single-Walled Carbon Nanotubes,” Science 27 January 2006: Vol. 311. no. 5760, pp. 508 – 51

University of Illinois at Urbana-Champaign news release