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Light is being used to detect diseases in blood and contamination in food thanks to research undertaken at the University of Wales College of Medicine in Cardiff and its spin-off company, Molecular Light Technology Research.

Biochemical studies of chemiluminescent (or light emitting) fish, insects and dyes led to the realisation that molecules obtained from acridine dyes can indicate disease in blood and tissue samples.

The chemiluminescent molecules work diagnostically by being joined to antibodies that recognise specific disease. So, for example, if hepatitis antibodies find traces of hepatitis in a sample they will make a beeline for it. Simultaneously, the chemiluminescent molecules illuminate the hepatitis, thereby indicating its presence.

A variety of conditions from TBto Aids can be diagnosed this way. The procedure is quick (a TB sample can be analysed in a couple of hours) and very sensitive. Minute amounts of disease, as small as a billionth of a gram, can be found.

Chemiluminescent testing is now being extended to other industries, such as food and water. Light-emitting antibodies have been developed to detect salmonella and listeria in food, and others are being created to pinpoint pesticides in rivers and bacteria on beaches.