"In its broadest sense, fibrin sheets may represent a new class of biological membrane and protein polymer. Cellular lipid membranes are the only other form of naturally occurring extended 2D molecular-scale sheets thus far known. Fibrin sheets are fundamentally different from the fibrin films formed from compressed clots, as first described in the work of Ferry and Morrison (27). Whereas those films were made from compressed clots, the sheets we describe are able to self-assemble in situ at physiological pH and ionic strength, are molecularly thin and uniform, and require no outside forces or manipulation to form. Here we present the first description of fibrin sheets and their physical properties. We were also able to record movies of sheet polymerization on the SSs, using fluorescently labeled fibrinogen, and to obtain estimates of the rates of assembly. Finally, we use TEM of fixed samples to show that fibers and small fiber networks transition structurally from sheets, and describe a preliminary model of how this might take place."

https://www.pnas.org/doi/10.1073/pnas.0804865105