As nouns the difference between collagen and fibrin
is that
collagen is any of more than 28 types of glycoprotein that forms elongated fibers, usually found in the extracellular matrix of connective tissue while
fibrin is a white, albuminous, fibrous substance, formed in the coagulation of the blood.
As a verb fibrin is
apply fibrin sealant to a surgical site to either stop bleeding or for surgical flap closure.