This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Wound Healing, Tissue Repair and Scar, Subject name: Surgery
All of the following are skin substitute except: 
Select and explain. 
A. Duoderm, B. Integra, C. Alloderm, D. Trancyte
A: Duoderm
Answer: A: Duoderm 
Explanation: - Skin substitutes are a type of dressing which is naturally derived from cells, extracellular matrix components or other components of skin. - It includes: Integra: A bilayered membrane skin substitute. AlloDerm: An acellular cadaveric dermis. Apligraf: A living bilayered biologic dressing composed of neonatal dermal fibroblasts on a collagen matrix. Trancyte: A tissue-engineered skin substitute is made from a nylon mesh and a silastic semi permissible and biocompatible layer. Duoderm is not a skin substitute it is a type of hydrocolloid which is composed of hydrocolloid matrix (gelatin, pectin, carboxymethylcellulose)