Hologram test for pregnancy

September 19, 1997

Biotechnology breakthroughs: starch and evening primrose oil yields and the use of holograms

Routine tests such as those carried out for pregnancy and measuring blood glucose levels could be revolutionised by the results of a research project at Cambridge University's Institute of Biotechnology.

A research team there is using holography to produce tests that could be sold over-the-counter at a lower price than existing kits.

Prototypes of the tests use a thin layer of a photosensitised polymer. A laser is shone through it and the light reflected by a mirror generates a stationary wave, which leaves bands on the polymer with either a high or low refractive index.

Chris Lowe, project leader and director of the institute, said the colour produced when white light is introduced depends on factors such as the average reflective index between the "micro-mirrors" on the polymer and the distance between them. The colour reflected is used as an indicator of the test results.

"The beauty of holography is that we can adapt it to a whole range of applications," he said. "Any mechanism where you can change the average refractive index, or spacing of the 'micro-mirrors', allows you to give a colour change."

The technique is being adapted to measure water, humidity, ions, enzyme activity, proteins and other biological molecules.

In the case of a humidity test, which is likely to be the first produced, "in a very wet atmosphere, the polymer swells, and you get a colour. If it is a very dry atmosphere, the water is taken out and the gel contracts and changes colour", Dr Lowe said.

Other possible applications include measuring the amount of solvents in water, or the level of water in solvents. As the population ages, the innovation could produce savings for hospitals conducting multiple tests on patients.

Three companies have expressed an interest in the test, which will be available in around two years. The institute is considering setting up its own company to market the development.

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