Monday, September 24, 2007

In charge of biosensing

A scanning probe microscope capable of detecting changes in the electrical charge on a surface is described in a report online this week in Nature Nanotechnology. This technique offers a rapid and sensitive way to sense biological targets, such as DNA and proteins.

Kelvin probe force microscopy (KPFM) is named after Lord Kelvin who investigated how charge is generated when two different materials are brought into close contact. Although KPFM is an established method that has been used to detect biomolecules in microarrays, Angela Belcher and Asher Sinensky have now applied it to measure binding events at the nanoscale. By considering much smaller feature sizes than previously studied, this development has increased both the speed and sensitivity of the technique.

The authors patterned single strands of DNA, which are negatively charged, onto gold substrates and measured their KPFM response. When complementary ‘target’ DNA strands were captured on the surface, the charge density in a given area was doubled and easily detected with KPFM. In this way, Sinensky and Belcher demonstrate the selective sensing of DNA sequences taken from the genes of anthrax and malaria.

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