Biodegradable polymer which, edible films have gained more attention due to their environmentally-friendly characteristics, vast variety and availability, non-toxicity, and low cost. Biodegradable polymers have a long history, and since many are natural products, the precise timeline of their discovery and use cannot be accurately traced. One of the first medicinal uses of a biodegradable polymer was the catgut suture, which dates back to at least 100 AD. The first catgut sutures were made from the intestines of sheep, but modern catgut sutures are made from purified collagen extracted from the small intestines of cattle, sheep, or goats. The concept of synthetic
Guqin strings silk and also they were louder and more stable. A set could last many years and not break. The only drawback for traditionalists was that the strings had a harsh metallic sound which was considered inelegant. Another factor was that the strings could eventually wear the lacquer out requiring the qin surface to be repaired more often. Around 2007, a new set of strings were produced made of mostly a nylon core coiled with nylon like the metal-nylon strings, possibly in imitation of Western catgut strings. The sound is similar to the metal-nylon strings but without the metallic tone to