Human Serum Albumin (HSA) is a natural protein found in the human body. It has proven preferable to artificial mediums, ideal as a stabilizer in pharmaceutical and biotech products, effective as a drug delivery vehicle, and very useful in cryo preservation and cell culture, as well as in other applications.
https://www.hsaexcipient.com/Human_Serum_Albumin_HSA_Excipient_Applications.aspx