Growth factor release is a key function of these fibrin clots for tissue regeneration. Our previous study [16] demonstrated that CGF membranes compressed by the stainless steel compression device contain significantly higher levels of growth factors even after releasing approximately 85% of exudate. Repeated rinsing with PBS failed to completely remove the growth factors from CGF membranes. The rinsed CGF membranes retained angiogenic effects in ex vivo and in vitro experimental systems. Considered together, these data imply that significant amounts of the growth factors are secured in CGF membranes, specifically in fibrin fibers. Similar functions were found in A-PRF and PPTF membranes. Therefore, it is thought that two distinct mechanisms are involved in controlled release of growth factors in exudate-depleted fibrin membranes: growth factors adsorbed to fibrin fibers and growth factors caged in platelets aggregated on fibrin fibers.

The initial phase of growth factor release from fibrin clots is mainly attributed to simple diffusion. In contrast, the late phase, i.e., the delayed growth factor release, is probably due to degradation of fibrin fibers and platelet membranes. We think that these combined releasing mechanisms determine how long the individual fibrin clot types last for tissue regeneration. This complex process of growth factor release from PRF (CGF) membranes should be investigated more carefully by developing appropriate experimental conditions.