Which of these materials is considered synthetic?

Poly-lactic Glycolic Acid (PLGA) is considered a synthetic material because it is derived from the chemical synthesis of lactic acid and glycolic acid, both of which can be produced from renewable resources but are processed through industrial methods to create a polymer with controlled properties. PLGA is widely used in tissue engineering due to its biocompatibility and biodegradability, making it suitable for a variety of applications including drug delivery systems and scaffolds for tissue regeneration.

In contrast, collagen, chondroitin sulfate, and chitosan are all naturally occurring materials derived from biological sources. Collagen is a protein found in animal tissues, chondroitin sulfate is a component of cartilage, and chitosan is derived from chitin, which is found in the shells of crustaceans. These natural materials are often used in tissue engineering for their biological properties, but they don't carry the synthetic designation that PLGA does.