Detectors recently developed for astronomy are now helping biologists to analyse genes

New technology developed for astronomy or particle physics often finds much wider use in other sectors such as medicine. A classic example are charge-coupled detectors, or CCDs, which can count individual photons of light and are standard devices in telescopes, but are now found in all kinds of imaging instruments.

Two years ago, physicists at the University of Leicester, with expertise in solid-state detectors, got together with their biologist colleagues to see if they could develop technology to improve DNA identification needed for potentially powerful medical techniques such as genetic profiling. The result was the 'BioAstral' team consisting of space scientists George Fraser and Andrew Holland, and biologists Pat Heslop-Harrison and Trude Schwarzacher.

The team is hoping to make identifying DNA samples much more sensitive. In the near future, DNA-testing kits using micro-arrays of genes, are likely to become part of primary healthcare (including treatment at your local surgery) so they will need to be as reliable and fast as possible to ensure accurate medical diagnosis.

A standard way of identifying DNA is to 'tag' the sample with a chemical that fluoresces in ultraviolet light. Several different fluorescent labels can be used which emit light at different wavelengths. However, conventional equipment using a combination of optical filters to remove background light and detectors such as CCDs or photomultipliers are limited in efficiency, and can identify only between two and four labels in a series of DNA images.

Fortunately, space scientists have a new technology up their sleeves. Over the past 10 years, they have been developing devices that not only detect individual photons, as CCDs do, but also detect the energy, or colour, of each photon. These are called superconducting tunnel junctions (STJs) and work at ultra-low temperatures. The BioAstral team has been working on using STJ devices to detect biological fluorescence, and the work has now been patented.

Advantages of STJs

STJs have three key advantages: First, the photon-counting capability, where every photon gives a measured signal, provides ultimate sensitivity; secondly, being able to record the photon energy gives a spectrum that can be used to identify the fluorescent label and measure the amount of emission; and lastly, the background light is automatically separated from the fluorescence, thus removing the need for the filters. The combined features should enable more than seven different fluorescent labels to be identified in any given experiment.

The experimental work is being carried out with the European Space Agency's Space Science Department, which originally led the development of STJs. Results already show very high sensitivity, with the promise of a further 1000 times improvement with an optimised system.

The BioAstral team has attracted funding to establish an optical STJ capability at Leicester so as to continue this development work.

Reference: Frontiers website

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The BioAstral team (left to right): George Fraser, Pat Heslop-Harrison, Andrew Holland and Trude Schwarzacher