Characteristics of Sugar Surfactants in Stabilizing Proteins During Freeze–Thawing and Freeze–Drying

Sugar surfactants with different alkyl chain lengths and sugar head groups were compared for their protein-stabilizing effect during freeze–thawing and freeze-drying. Six enzymes, different in terms of tolerance against inactivation because of freeze–thawing and freeze-drying, were used as model proteins. The enzyme activities that remained after freeze–thawing and freeze-drying in the presence of a sugar surfactant were measured for different types and concentrations of sugar surfactants. Sugar surfactants stabilized all of the tested enzymes both during freeze–thawing and freeze-drying, and a one or two order higher amount of added sugar surfactant was required for achieving protein stabilization during freeze-drying than for the cryoprotection. The comprehensive comparison showed that the C10–C12 esters of sucrose or trehalose were the most effective through the freeze-drying process: the remaining enzyme activities after freeze–thawing and freeze-drying increased at the sugar ester concentrations of 1–10 and 10–100 μΜ, respectively, and increased to a greater extent than for the other surfactants at higher concentrations. Results also indicate that, when a decent amount of sugar was also added, the protein-stabilizing effect of a small amount of sugar ester through the freeze–drying process could be enhanced. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 103:1628–1637, 2014