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 in vitro 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.