Accepted answer
Nobody has published a cycle count, and at 2 mg/mL the concentration tells you what a wrong guess costs: a 0.1 mL aliquot holds 0.2 mg and every microlitre is 2 µg. Damage from freezing is not gradual attrition — it is concentrated at the phase transitions, where ice excludes solute and the unfrozen fraction climbs well above 2 mg/mL for as long as the transition lasts. Two slow cycles can therefore do more than four fast ones, which is why a cycle count is the wrong unit in the first place. The way to make the number one is to make it one: split at reconstitution into single-draw aliquots, label each with 2 mg/mL and the date, and never thaw a container you will refreeze.
The short version: aliquot before freezing, thaw slowly, never refreeze a thawed aliquot, and count your cycles.
Thaw slowly at room temperature or in the refrigerator rather than in warm water. Rapid warming creates local thermal and concentration gradients that promote aggregation.
Mechanically, a dry lyophilised powder is much less affected by a temperature cycle because there is no liquid phase for anything to concentrate into. Condensation on a cold vial opened warm is the real risk there.
Selective crystallisation of sodium phosphate buffer components producing large pH shifts on freezing is a classical result in the lyophilisation literature.
The number of tolerable cycles is sequence- and formulation-dependent and no general number is honest.
Dry powder tolerates cycles far better than solution does.
Does the same reasoning apply to material already in solution, or is that a different curve? – ines_brandt 4 months ago Thank you — this is the answer I was looking for. – g_paskevicius 3 months ago add a comment