SIMPLIFIED METHOD FOR FREEZING HUMAN-BLOOD PLATELETS IN GLYCEROL-GLUCOSE USING A STATICALLY CONTROLLED COOLING RATE DEVICE

An inexpensive, statically controlled cooling rate device consisting of a cassette of aluminum plates and cardboard insulation in a plastic bag was used to freeze platelets in liquid nitrogen with glycerol‐glucose as cryopro‐tectant. Depending on the thermocouple location, the cooling rate in the freezing bag varied between 22.1 and 38.6 C per minute, averaging 33.6 ± 1.1 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 per cent, compared to 86.1 ± 9.9 per cent for nonfrozen, but otherwise identically processed platelets. 14C Serotonin uptake after 0.5‐hour incubation was 95.9 ± 1.9 per cent for fresh platelets in platelet‐rich plasma, 92.7 ± 4.4 per cent for nonfrozen processed platelets, and 81.4 ± 11.8 per cent for frozen platelets, increasing to 85.9 ± 7.7 per cent after one‐hour incubation. 1979 AABB