The Telegraph
Since 1st March, 1999
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The new silk route
Proteins from the tussar silkworm increase the shelf life of L-Dopa

Subhas Kundu was always interested in silkworms. When the biotechnologist was a child growing up in a remote village in the West Midnapore district of West Bengal, he used to collect cocoons of tussar silkworms falling off Sal trees and exchange them in a neighbourhood shop for a handful of coloured sugar candies.

He is still collecting silkworms, but not for toffees. For long years, he has been studying the caterpillar — which gives us the finest variety of malmal silk. The head of the biotechnology department at the Indian Institute of Technology (IIT), Kharagpur, has shown that proteins extracted from these worms can play a critical role in bone repair, grafting, delivery of drugs and even in the treatment of diseases such as Parkinson’s.

While mulberry silk, reeled from the domesticated silkworm Bombyx mori, accounts for the lion’s share of silk products globally, there are several wild silk moths such as those that yield prominent silk varieties like tussar, muga and eri.

Silkworm cocoons, be it mulberry or non-mulberry, contain two major proteins — fibroin and sericin. While the fibrous protein fibroin — which constitutes nearly 70 to 80 per cent of the cocoon’s weight — is responsible for silk fibres, sericin acts more like glue and holds the fibres together. Sericin, which is at present thrown away, has potential pharmaceutical, cosmetics and biotech applications.

For instance, Kundu’s team has used these proteins (isolated from the glands of the tussar silkworm or the Antheraea mylitta) in making films, scaffolds, hydrogels and nanoparticles that can be used in medical applications such as wound dressing, skin grafting and even in the delivery of drugs and other bioactive molecules inside the human body. All these new products are in different stages of development, Kundu told KnowHow.

Another important development recently reported by the IIT, Kharagpur, scientists is that the silkworm protein extends the shelf life of a crucial drug, L-Dopa, which is used to treat Parkinson’s disease. L-Dopa seeks to substitute a brain chemical called dopamine that gets lost in the disease. But it’s very difficult to store the drug, for it becomes completely ineffective within a few days if exposed to oxygen and light.

The researchers have now found that if L-Dopa is held together by a matrix made of the silkworm’s fibroin protein, it is effective even after 10 days. “This, I believe, can be an important feat in the management of Parkinson’s,” says Kundu.

Kundu is not alone in this quest for finding novel applications for silk whose properties, such as its smooth texture, shimmering appearance and strength, have made this natural fibre the darling of textile designers all over the world. Researchers in countries like China, Japan and Korea have several silk-based non-textile products such as mulberry tea, nutritive supplements rich in antioxidants and many others.

Sutures made of biocompatible silk fibre have been in use for surgeries for some time now. Scientists elsewhere are even trying to develop blood vessels and heart valves using the fibre.

Kundu thinks that finding high-value application for the Indian silk varieties, which are already suffering from an onslaught from the cheaper mulberry silk from China, can help poor farmers involved in sericulture.

“Going beyond textile applications is the way forward for the silk industry,” says Kanika Trivedi, a researcher at the Central Sericultural Research and Training Institute, Mysore.

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