Differentiating α-synuclein aggregates using charge-sensitive gold nanoclusters

The accumulation of α-synuclein (α-syn) aggregates in the brain is associated with Parkinson's disease, making it a promising biomarker for understanding the disease's pathogenesis. Distinguishing between oligomeric forms of amyloidogenic proteins is crucial, as their toxicity depends on conformation. This study leverages surface charge differences to distinguish α-syn monomers from amyloids. We employed label-free gold nanoclusters (AuNCs) with distinct surface charges to differentiate between wild-type and mutant [A30P]-α-Syn based on their charge characteristics. Fluorescence spectroscopy and electrochemical measurements were performed to evaluate the sensitivity and interaction mechanisms. Our results show that Pro-AuNCs exhibit greater sensitivity towards monomeric forms of both wild-type and mutant α-Syn, while His-AuNCs are more sensitive to amyloid forms. Impedance spectroscopy shows a detection limit in the picomolar range (pM), which is twice as sensitive as fluorescence measurements. Cell culture studies further validate our <i>in vitro</i> findings, demonstrating the effective specificity of AuNCs for detecting different conformations of α-syn. Overall, our results indicate that this probe can successfully identify aggregated and monomeric forms of α-syn, suggesting its potential for developing sensors aimed at understanding the etiology of Parkinson's disease.