Studies with dextran 40 in cryopreservation of blood

Abstract

Whole blood from healthy donors was washed twice with phosphate-buffered saline (PBS) and then resuspended in sufficient PBS to give a final concentration of 2 × 10 9/cells/ml. Aliquots were combined with equal volumes of the required diluents to give final dextran 40 concentrations of 0, 5, 10, 15, and 20% in PBS. Fifty-lambda samples in 50-lambda Micropets (Clay Adams) were frozen in alcohol baths at temperatures ranging from −10 to −80 °C. The specimens were frozen either for 1 min or 16 min, rapidly thawed, and resuspended in PBS or PBS plus dextran. Percentage of hemolysis was determined colorimetrically. Results indicate that concentraitons as low as 5% dextran exert a cryoprotective effect. Increased dextran concentration increases cryoprotection at high subzero bath temperatures (−10 ° and −20 °C). Dextran concentrations beyond 12% have a damaging effect at low subzero bath temperatures (below −30 °C). Based on this a two-factor hypothesis for cryopreservation is proposed. Apparent partial recovery of red blood cells without dextran or with 5% dextran during subzero storage was demonstrated.