Properties of Fibrin Film

When water-equilibrated film is pressed between moist layers of absorbent material, the fibrin content is readily increased from 30% to 40% with very little pressure. To expel water beyond this point requires much higher pressure at 30 

Opacity. When water is removed from water-equilibrated film either by compaction or by partial drying, the opacity decreases and the film becomes transparent when a fibrin content of 60% is attained. When the transparent pressed film is allowed to imbibe water, the opacity, like the fibrin content, returns to its original value. The optical density per unit thickness of film is plotted against the fibrin content in Fig. 32. There is a much more marked change below a concentration of 40% fibrin than above this value these data, like those for the pressure required for compaction, suggest some structural transition at a fibrin content of 40%. 

The opacity of fibrin film is much diminished when the water it contains is replaced by glycerol this effect is attributed to the fact that the refractive index difference between protein and glycerol is much less 

Porosity, From the rate of flow of water through thin fibrin film, rough estimates of the size of network interstices have been calculated as 45-100 A. From the fact that hemoglobin molecules pass readily through these films, it is concluded that the interstices are at least 40 A. wide. Moreover, the course of digestion of fibrin film by plasmin 

Mechanical Properties. Water-equilibrated fibrin film can be stretched to two to three times its initial length, and, unless held for some time in the stretched state, returns to its original shape when the load is removed. The response to stress is not as rapid as in true rubberlike materials, and the film undergoes slow creep under constant load, as well as slow creep recovery after removal of load. Furthermore, stress-strain curves over cycles of elongation and contraction exhibit marked hysteresis. 

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Ferry, J. D., and Morrison, P. R. (1945). The Physical Properties of Fibrin Films Prepared from Human Fibrinogen and Thrombin. II. Interim report under Contract OEMcmr-139 with the Committee on Medical Research and Development. 

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