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 for the archery 'bow'. It is important to distinguish from the two as they are often used to refer to the strings of the qin, or any other stringed instrument, sometimes together on the same page. However, etymologically, 『絃』 is the correct character to be used to refer to strings of the qin as the radical denotes, qin strings were made of silk (though probably etymologically incorrect for the modern metal-nylon strings). But for 『弦』, it probably denotes a string used on an instrument which requires a bow to play, such as erhu or violin. Maybe, 『弦』 can also be