New technique seals diseased blood vessels with a zap of laser light

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London, June 13 : An international team of researchers has developed a laser sensitive drug, which can close of blood vessels to treat certain tumours or a common eye disease. The new technique developed by the team of Canadian, American and British researchers is an advancement of the present photodynamic therapy (PDT) in which a light-sensitive compound is injected into the diseased tissue.

When the compound is exposed to laser light, it produces a high-energy form of oxygen that is poisonous to cells.

In the study conducted using a mouse model, scientists were able to seal diseased blood vessels with tremendous accuracy with a flash of laser light.

While using the standard PDT, it becomes difficult to focus on the impact on diseased cells without destroying adjacent healthy tissue, moreover, the laser light needed can only penetrate 1 centimetre into the tissue.

However, a research team led by Brian Wilson of the University of Toronto, Canada have developed a novel compound that can successfully handle both problems.

Unlike, the present PDT compounds, each molecule of the new drug is able to absorb two photons instead of just one.

The drug exhibits a physical phenomenon known as two-photon excitation, which means much less energy is needed to perform the procedure.

As a result, low-energy near-infrared light can be used, which can penetrate two or three times deeper into living tissue, depending on the particular tissue. That would allow many more uses for PDT.

During the study, researchers were able to close blood vessels with "exquisite spatial selectivity", using pulses of laser light to "draw" along vessels they wanted to close.

"The most immediate application is treating [advanced] age-related macular degeneration (AMD) by closing off unwanted blood capillaries," New Scientist quoted Harry Anderson, lead researcher from the University of Oxford.

"It might also be used to treat certain tumours, particularly where improved accuracy is required," he added.

The team would now be conducting further studies analysing the toxicology of the new photosensitive drug, and its efficacy against tumours.

"This paper is a breakthrough in two-photon PDT and I would mark it as in the top five important results for biophotonics in the past year," said David Cramb of the University of Calgary, Alberta, Canada, who also works on PDT.

ANI

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