Design of an Ice Recrystallization-Inhibiting Polyampholyte-Containing Graft Polymer for Inhibition of Protein Aggregation

Freezing-induced damage to proteins, through osmotic stress and ice recrystallization, during protein processing and long-term storage is a serious concern and may lead to loss of protein activity owing to denaturation. In this study, graft copolymers composed of a cryoprotective polymer (capable of preventing osmotic stress) and poly(vinyl alcohol) (PVA; known for its high ice recrystallization inhibition (IRI) property) were developed. The polymers had high IRI activity, albeit slightly lower than that of PVA alone, but substantially higher than that of succinylated ε-poly-l-lysine (PLLSA) alone. The graft polymers showed an efficiency higher than that of PVA or PLLSA alone in protecting proteins from multiple freeze-thaw cycles, as well as during prolonged freezing, indicating a synergy between PVA and PLLSA. The PLLSA-based graft polymer is a promising material for use in protein biopharmaceutics for the long-term storage of proteins under freezing conditions.