Amino Acid-Based Polymer-Coated Silver Nanoparticles as Insulin Fibril Inhibitors

Abstract

To explore the impact of polymer-coated silver nanoparticles (PC-AgNPs) on the extent of the insulin aggregation process, herein, we have synthesized three copolymers comprising poly(ethylene glycol) methyl ether methacrylate (PEGMA) and tert-butoxycarbonyl (Boc)-protected amino acid (alanine, leucine, and phenylalanine) containing methacrylate monomers, via reversible addition-fragmentation chain transfer (RAFT) polymerization. After deprotection of the Boc groups, the as-prepared water-soluble copolymers were coated on silver nanoparticles (Ag NPs), and the role of these NPs on insulin aggregation pathways was examined by multifarious spectroscopic and microscopic techniques. The extent of the inhibitory effect against the insulin fibrillation process was found to be related to the surface properties of the NPs, with the highest inhibitory effect detected for phenylalanine-based polymer-coated Ag NPs (PPhe-AgNPs). Using circular dichroism (CD) spectroscopy and Nile red (NR) fluorescence spectroscopy, we investigated the conformational changes and examined the role of hydrophobic interaction in inhibiting the aggregation properties of insulin upon treatment with PC-AgNPs. Furthermore, PC-AgNPs were also able to disintegrate the matured insulin fibrils and efficiently decreased the fibril-induced cytotoxicity, as confirmed by transmission electron microscopy (TEM) and the hemolysis study, respectively. Together, our findings established the novel amino acid-based PC-AgNPs as potent nanomaterials with 77–96% insulin fibril inhibition and marked disaggregation of matured insulin fibrils.