Colored Cocoon Silk

Environmentally benign dyes are used in the textile industry to reduce pollution. An attempt was been made to produce dyed silk cocoons. This was achieved by feeding modified mulberry leaf food containing dye spray solution to the silkworm larvae, Bombyx mori. This method greatly reduced the need to deal with dyes used in conventional dyeing. Seven different commonly used azo dyes had been reviewed for dyeing to make colored cocoon silk. The dyes used had similar chemical structures, but the distribution coefficients were changing systematically. The physical properties of those related azo dyes indicate that a balance between hydrophobicity and hydrophilicity is needed to enable the dye to diffuse from the digestive tract of silkworm larvae to the lymph, and then to the silk glands. Preferred association of the dye with the sericin or silk protein in the silkworm glands and finally in the cocoons are determined by distribution coefficient of the dye. These findings are extremely important for the development of new dye molecules that can successfully feed silkworm larvae.