It’s February. For most people, this month conjures up thoughts of Valentines, romantic dinners, chubby toddlers wielding bows and arrows, and copious quantities of chocolate….which leads me to this month’s featured product: Insulin.
Insulin, like many other biological components, is often stored and sold as a lyophilized powder. This assures the buyer that the insulin is stable, has retained its activity, and it is likely to last longer in the lab.  While it is typically shipped at ambient temperature (with no real impact on it stability or performance), it should be stored at -20oC as soon as it hits your lab. 
Reconstitution of insulin may vary from lab to lab, but the general idea is that because insulin has poor solubility at pH levels at or near 7, it should be reconstituted in a weakly acidic solution.  Some folks use acetic acid, others  may use HCl. Whatever the acid used, the pH should be between 2 and 3 to ensure complete solubilization of the insulin powder. Sounds easy enough and it is, really.  Additional measures to increase longevity of your insulin is to add a carrier protein to the mix. Typically researchers use 0.1% BSA or HSA.
Once reconstituted, the insulin can be aliquotted and stored at 4oC for immediate use (roughly a week or less) and at -20oC for longer term storage.
That’s about all I have for solubilizing insulin. The folks at Gemini are always happy to answer questions and help troubleshoot issues so don’t hesitate to pick up the phone or start typing your questions to them.  Stay tuned for next week’s blog. I’ll be tackling the issue of how we can start to determine which insulin we should be using.