Amphiphilic Surface Chemistry Of Fullerenols Is Necessary For Inhibiting The Amyloid Aggregation Of Alpha-Synuclein Nacore

Featuring small sizes, caged structures, low cytotoxicity and the capability to cross biological barriers, fullerene hydroxy derivatives named fullerenols have been explored as nanomedicinal candidates for amyloid inhibition. Understanding the surface chemistry effect of hydroxylation extents and the corresponding amyloid inhibition mechanisms is necessary for enabling applications of fullerenols and also future designs of nanomedicines in mitigating amyloid aggregation. Here, we investigated effects of C-60(OH)(n) with n = 0-40 on the aggregation of NACore (the amyloidogenic core region of the non-amyloid-beta component in alpha-synuclein), the amyloidogenic core of alpha-synuclein, by computational simulations, transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, thioflavin-T (ThT) fluorescence kinetics and viability assays. Computationally, NACore assembled into cross-beta aggregates via intermediates including beta-barrels, which are postulated as toxic oligomers of amyloid aggregation. Hydrophobic C-60 preferred to self-assemble, and NACore bound to the surface of C-60 nano-clusters formed beta-sheet rich aggregates - i.e., having little inhibition effect. Amphiphilic C-60(OH)(n) with n = 4-20 displayed significant inhibition effects on NACore aggregation, where hydrogen bonding between hydroxyls and peptide backbones interrupted the formation of beta-sheets between peptides adsorbed onto the surfaces of fullerenols or fullerenol nano-assemblies due to hydrophobic interactions. Thus, both cross-beta aggregates and beta-barrel intermediates were significantly suppressed. With hydroxyls increased to 40, fullerenols became highly hydrophilic with reduced peptide binding and thus an inhibition effect on amyloid aggregation. ThT, FTIR and TEM characterization of C-60(OH)(n) with n = 0, 24, & 40 confirmed the computational predictions. Our results and others underscore the importance of amphiphilic surface chemistry and the capability of polar groups in forming hydrogen bonds with peptide backbones to render amyloid inhibition, offering a new insight for de-novo design of anti-amyloid inhibitors.