'Super-twisted' light enables biodetection at super low concentrations

Researchers at the University of Glasgow (Scotland), in conjunction with physicists at the University of Exeter (UK), report they have succeeded in producing super-twisted light, which had previously only been theorized.1 Polarized or twisted light is already used in some medical techniques to analyze biomolecules, but the Glasgow-led team has been able to achieve greater power by twisting the light even tighter.

The super-twisted light is useful for life sciences because it can detect protein traces in an incredibly small sample of blood or other biological material (just one picogram)—far less than other analytical methods require. The researchers have discovered that super-twisted light is particularly sensitive to proteins with a structure characteristic of amyloids—the insoluble proteins that can stick together to form plaques and are associated with degenerative diseases such as Alzheimer's and Parkinson's.

Click to Enlarge
This diagram illustrates the operation of super-twisted light (red), which results when a beam from a spectrometer lamp is projected onto a 400 nm gold particle, which re-emits the light in a tightly twisted form.

The technique takes advantage of the fact that light can be turned like a corkscrew by passing it through a special polarizing filter. "The [filter] structures we use are fabricated out of gold using lithography and are 400 nm across. They are irradiated with light from a lamp in a spectrometer, this light is absorbed by the nanosctructures and then re-emitted in a super-twisted form," senior lecturer Malcolm Kadodwala told BioOptics World. "We're now looking to see if this same technique can be adapted to detect a wider range of proteins, which are indicative of other diseases."

Using super-twisted light in spectroscopy also has potential for biosensing, such as detecting viruses with similar structures.

1. E. Hendry et al., Nature Nanotechnology 5: 783-787 (2010)

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