Fetuin, Fetal Bovine Serum is a glycoprotein weighing 64 kDa that is secreted by the liver and obtained from fetal bovine serum. It acts as an inhibitor of trypsin activity and facilitates cellular attachment, growth, and differentiation.

Fetuin, Fetal Bovine Serum is often an important supplement to many serum-free media[2]. Fetuin is an acidic glycoprotein with three N-linked and three O-linked oligosaccharide chains, whose terminal sugar residues are rich in sialic acid (N-acetylneuraminic acid), contributing to its net negative charge[3].