Scientists Use "Green" Solvents to Turn Silk Into Life-Saving Medical Materials

Scientists around the world are using special eco-friendly chemicals called green solvents to turn silk from silkworms into powerful medical materials. These materials could one day help doctors treat serious diseases like heart disease, diabetes, cancer, and bone disorders. The research brings together ideas from biology, chemistry, and medicine to find better, safer ways to help the human body heal. Best of all, this new approach tries to protect the environment at the same time.

Silk is a natural material made by silkworms, and the most common type used in medicine comes from the mulberry silkworm, called Bombyx mori. Silk is made of two main proteins: silk fibroin and sericin. Sericin acts like a glue that holds the silk fibers together. Scientists mainly use silk fibroin in medicine because it works well with the human body, is very strong, and can be shaped into many useful forms.

Silk fibroin has already been approved by the U.S. Food and Drug Administration to be used in certain medical devices. To use it in medicine, scientists first need to dissolve it — turning it from a solid into a liquid. In the past, they used harsh chemicals to do this, but those chemicals could be toxic and harmful to the environment. Researchers have been searching for cleaner options that work just as well but are safer for people and the planet.

That's where green solvents come in. Green solvents are chemicals that are better for the environment and, in many cases, safer for living things. Three important types used with silk are ionic liquids, biocompatible ionic liquids, and deep eutectic solvents. Each type has its own strengths, but all of them can help dissolve and reshape silk fibroin in useful ways. Using these solvents also reduces waste because they can often be reused or recycled.

Ionic liquids were among the first green solvents used to dissolve silk fibroin. Scientists found that certain ionic liquids could break apart the silk protein at a tiny, molecular level, letting large amounts of it dissolve. This made it easier to create silk fibers and other silk-based shapes for medical use. Ionic liquids also allowed scientists to mix silk fibroin with other materials like cellulose and chitosan to create stronger or more useful products.

However, some ionic liquids can be harmful to living cells if too much is left behind in the finished material. Scientists must carefully wash out the ionic liquid after making the silk product and use special tests to confirm it has been fully removed. Because different ionic liquids behave differently, each one needs its own safety review before it can be used in a medical product. Researchers agree that no single safety rule works for all of them.

A newer type called a Bio-IL is helping solve some of these problems. Bio-ILs are made from ingredients that are friendlier to living things, such as amino acids and natural acids. They still have many useful properties of regular ionic liquids but break down more easily and are less likely to harm cells. Scientists have already used Bio-ILs to create silk-based sponges, gels that carry electrical signals, and other advanced medical structures.

Deep eutectic solvents are another exciting group of green solvents. They can turn raw silk fibers into incredibly tiny particles called silk nanofibers, which are very useful for medical applications. Deep eutectic solvents have also been used to make silk materials that can stretch, carry electricity, and even change shape when exposed to heat. These unique abilities open up many possibilities for building advanced medical tools and devices.

Scientists have proposed using these green silk-based materials for many important medical purposes. These include repairing heart tissue, regrowing cartilage, healing spinal cord injuries, delivering drugs, closing wounds, and building tiny electronic devices that can work inside the body. More tests are still needed to make sure the materials work safely inside living animals and humans before they can be used in clinics. Even so, the future of green silk medicine looks very promising.