Determination of drug levels in human serum by circular dichroism

Cryopreserved skin must be used immediately after thawing or discarded owing to rapid post-thaw deterioration in viability. This is inconvenient and wasteful. The purpose of this study was to evaluate whether release of protease enzymes from cryogenically damaged cells or the action of free radicals on skin cells, is the cause of this deterioration. Following thawing. skin was incubated for 24 h at 4 degrees C in a range of protease inhibitors and free radical inhibitors/scavengers. The rate of deterioration was significantly reduced by using complex treatments including addition of serum, egg white and raised pH. These treatments are known to inhibit various groups of protease enzymes but would clearly have additional effects on the cells. Of the remaining treatments most of the specific protease inhibitors improved viability although not significantly. Treatments designed to inhibit or scavenge free radicals had little or no effect.