Silk, with a nano touch, promises new industrial applications

Silk infused with nanomaterials is piquing research interest even as it starts to find applications across sectors. A team of Indian researchers has used carbon dots to modify silk, five millennia since its discovery, in a study that could unlock new industrial possibilities with the material.

The carbon dots-embedded silk fibre, they said, could be used in products as diverse as gas sensors and smart textiles, and aid biomedical analysis. In a paper that validates the concept, the researchers have proposed the use of modified silk fibres for the precise detection of dopamine, the neurotransmitter which shapes human emotions and perceptions.

The researchers obtained fluorescent silk fibres from silkworms by feeding them carbon dots (carbon nanomaterials) that were sprayed on the silkworm feed. These fibres, exhibiting blue fluorescence, were found to help in detecting dopamine even in low concentrations, up to 4.39 nM (nanomolars).

Varsha Lisa John and Vinod T P, at Christ (Deemed to be University), Bengaluru, worked with T R Keerthi and A R Nayana from Mahatma Gandhi University, Kottayam, and B C P Sasidharan and Athira Krishnan K A from Cochin University of Science and Technology, to develop the silk fibres. Their findings were published in the peer-reviewed journal Macromolecular Bioscience.

The carbon dots were synthesised from the morus rubra variant of mulberry leaves and sprayed on the leaves the silkworms feed on. Vinod, an associate professor in the Department of Chemistry, Christ, said the carbon dots came embedded in the silk fibre, unlike in the more prevalent practice of modifying the fibre after it is derived from the silkworms.

The fibre also displayed greater mechanical stability, he said.

The modified fibres were exposed to a fluorescence test with dopamine hydrochloride, added in varying concentrations. The test showed a quenching response, or a decrease in fluorescence intensity, when dopamine was added sequentially. “Carbon dots exhibit fluorescence with a certain intensity and wavelength. The variations in this fluorescence were recorded to validate their sensitivity to dopamine,” Vinod told DH.

Synthesising carbon dots from mulberry leaves and using fluorescent silk fibres to design a dopamine-sensing assay is a first in India, he said. The findings also signify possibilities for the future. “These silk fibres, when modified with other functional materials, present greater applications – as materials for wound dressings, for instance,” Vinod said. The paper noted that detailed studies on carbon dots’ influence on larvae growth and determination of permissible dosage levels would enable the upscaling of the technique.