Experimental Investigation Of Freeze-Drying Of Human Platelets

Platelet transfusion has many applications in clinical medicine. Therefore the development of preservation method that will increase platelet lifespan and improve platelet quality in vitro is desirable. Freeze-drying is one potentially ideal approach for long-term preservation of platelets. Freeze-dried platelets can be stored at room temperature for a long time, have a low mass that can be readily transported and can be reconstituted by rehydration at the point of use. However, freeze-drying of platelets still has many unsolved problems and is far away from the clinical application. This dissertation studied the freeze-drying of human platelets and aimed at improving the survival rate of freeze-dried platelets. Following work has been carried out:A set of laboratory freeze-drying equipment was built. A new auto-cascade refrigerating cycle was used as its refrigeration system. The temperature of the shelf reached below -60 ℃ and the temperature of the cold condenser reached below -80 ℃. The temperature, pressure and weight of the sample can be measured and controlled precisely, providing necessary conditions for freeze-drying of platelets.The glass transition temperatures of platelet formulation were measured by differential scanning calorimetry for both suspension and freeze-dried sample. The factors that influenced the glass transition temperatures of suspension and freeze-dried sample were investigated. The addition of bovine serum albumin increased the glass transition temperatures of suspension and freeze-dried sample. The glass transition temperature of suspension increased with trehalose concentration, while the glass transition temperature of freeze-dried sample was almost not affected by solution concentration. The glass transition temperatures of suspension and freeze-dried sample of trehalose, lactose and maltose are high and close to each other, sucrose is a little lower, and glucose is far lower than other sugars. Platelet concentration almost has no effects on the glass transition temperatures of suspension and freeze-dried sample. Except for the formulation of 20% glucose, the lowest glass transition temperature of suspension is -36.2 ℃, the lowest glass transition temperature of freeze-dried sample is 35.3 ℃. According to these results, the freezing temperature is determined at -40 ℃, the drying temperature is determined at -38℃ and the storage temperature is determined at room temperature below 30 ℃ during freeze-drying of platelets.