A 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 cryoprotectant. 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.