Examining the effects of dextran-based polymer-coated nanoparticles on amyloid fibrillogenesis of human insulin.

More than thirty human proteins and/or peptides can aggregate to form amyloid deposits that are linked to several amyloid diseases including clinical syndrome injection-localized amyloidosis, which is correlated with the aggregation of the 51-residue polypeptide insulin. While no cure is currently available toward tackling amyloid diseases, prevention or suppression of amyloid fibrillization is considered as the primary therapeutic strategy. Nanomaterials have been demonstrated to possess great potential in the fields of biomedical diagnosis and drug delivery, they are also able to affect the amyloid aggregation of proteins. This work explores the effects of three different magnetic nanoparticles coated with dextran-based polymers on the in vitro amyloid fibrillogenesis of human insulin. Surface modification of nanoparticles with dextran-based polymers was used to improve the biocompatibility of maghemite nanoparticles. We demonstrated that insulin fibrillization may be mitigated by the studied nanoparticles in a concentration-dependent fashion as verified by ThT binding assay and transmission electron microscopy. The extent of inhibitory activity against human insulin fibril formation was found to be associated with the physico-chemical properties of nanoparticles, with the highest inhibitory activity observed for diethylaminoethyl-dextran-coated nanoparticles. Using circular dichroism spectroscopy, ANS fluorescence spectroscopy, and right-angle light scattering, we probed the structural/conformational changes and investigated the aggregating behavior of insulin upon treatment with nanoparticles. This work demonstrates that nanoparticles with an appropriate surface modification can be utilized to suppress or even inhibit amyloid fibril formation of proteins.