Zwitterionic Polymer Design that Inhibits Aggregation and Facilitates Insulin Refolding: Mechanistic Insights and Importance of Hydrophobicity.

The synthesis of a zwitterionic polymer, poly-sulfobetaine (poly-SPB), which shows remarkable efficiency in the suppression of insulin aggregation is described. Hydrophobic modification of the polymer results in almost complete inhibition at very low polymer concentrations. Further studies reveal that these polymers facilitate the complete retention of insulin's secondary structure, which is otherwise lost after incubation. Refolding studies show that addition of polymers to preaggregated insulin sample leads to the refolding of denatured insulin, indicating their potential to facilitate the refolding of the denatured proteins. In addition, 2D NMR studies show that the presence of hydrophobic poly-SPB alters the hydrophobic environment of insulin, which may suppress hydrophobic interactions that lead to aggregation. These results indicate the enormous potential of these polymers for suppressing insulin aggregation and provide significant insight into the complex mechanism of insulin protection by zwitterionic polymers.