Abstract: An inexpensive, statically controlled cooling rate device comprising a cassette of metal plates and cardboard insulation in a plastic bag was used to freeze platelets in liquid nitrogen with glycerol-glucose as cryoprotectant. Depending on the thermocouple location, the cooling rate in the freezing bag varied between 22.1.degree. and 38.6.degree. C. per minute, averaging 33.6.degree..+-.1.1.degree. C. per minute at the center. The post-thaw recovery of platelets frozen with this device and reconstituted in plasma averaged 88.6.+-.11.7 percent, compared to 86.1.+-.9.9 percent for nonfrozen but identically processed platelets. [.sup.14 C]Serotonin uptake after 0.5-hour incubation was 95.9.+-.1.9 percent for fresh platelets in platelet-rich plasma, 92.7.+-.4.4 percent for nonfrozen processed platelets, and 81.4.+-.11.8 percent for frozen platelets, increasing to 85.9.+-.7.7 percent after one-hour incubation.

Abstract: A frozen proteinaceous mass comprising blood platelets coated with glycerol-glucose, the frozen mass prepared by a process comprising:A. contacting blood platelets with an aqueous saline solution containing 4 to 7 weight percent glycerol and glucose 2 to 6 weight percent in an at least 5 : 1 volume to volume solution : platelet ratio;B. removing supernatant liquid;C. concentrating platelets to about 20 mg platelets protein per ml.D. thereafter freezing the platelets at a rate of at least 20.degree. C per minute.