FREEZE-DRYING OF SMALL TISSUE SAMPLES AND THIN FROZEN SECTIONS BELOW –60°C A SIMPLE METHOD OF CRYOSORPTION PUMPING

Abstract

Freeze-drying rates for three tissues have been determined by direct measurement of weight loss in a closed system, using an electrobalance. The half-drying times (T/2) at approximately 1 x 10–5 mm Hg with Dry Ice slush as coolant were determined for brain, kidney and liver and found to be 100, 50 and 30 hr, respectively, for 10-mg samples of tissue. A method for the freeze-drying of frozen sections in which the temperature of the tissue is maintained below –60°C throughout sectioning and drying is discussed. A simple portable, all glass, freeze-drying system utilizing cryosorption pumping is presented.