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.
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