Formation of a cryogel during processing of cell-free plasma

Automated plasmapheresis devices are being integrated into many modern plasma procurement programs. Owing to the use of a different concentration and type of anticoagulant, the recovered plasma differs in pH and citrate levels from that obtained by manual plasmapheresis or whole blood donation. Recently, fractionators noted the recovery of a sticky, gelatinous fraction (cryogel) during thawing of cell-free (CF) plasma, along with reduced recovery of factor VIII:C (FVIII:C) in the cryoprecipitate fraction. Following their manufacturing procedures, it was established that the cryogel fraction of CF plasma is enriched in FVIII:C, fibrinogen, and fibronectin, as compared to cryoprecipitate from CPDA-1 plasma. Cryogel formation was not significantly affected by pH or citrate adjustment of the recovered plasma, by the use of polycarbonate or nylon filter membranes, or by the filter wetting agent polyvinylpyrrolidone (PVP). Furthermore, passage of CPDA-1 plasma through the polycarbonate filter did not alter cryoprecipitate quality. However, cryogel formation from CF plasma was reduced significantly by 1) slow thawing at 4 degrees C rather than quick thawing at 20 and 0 or 20 and 4 degrees C, 2) the use of 1:16.6 sodium citrate rather than 1:12.5 ACD-A, or 3) the addition of intact platelets, platelet lysate, membranes, or cytosol to CF plasma before freezing. The data suggest an important and, indeed, essential role of platelet constituents in the formation of both cryoprecipitate and cryogel during the low-temperature purification of plasma proteins.