Ultrasonic detection of α-synuclein amyloid seeds from a highly crowded environment.

Detecting α-synuclein (α-Syn) amyloid seeds in biological fluids is a promising approach for the early diagnosis of Parkinson's disease. However, detecting subtle amounts of seeds in highly crowded environments remains challenging. Ultrasonication can enhance seed detection by efficiently fragmenting fibrils, but its effects in crowded environments have not been fully explored. In this study, we apply ultrasonication to detect α-Syn seeds in a highly crowded milieu and investigate its effects on seed detection. Our results show that ultrasonication enables rapid detection of α-Syn seeds with a detection limit of 10 pg/mL, even in the presence of 40 mg/mL serum albumin. Intriguingly, the amount of fibril formed depends on the initial seed concentration in a crowded environment only under ultrasonication. To understand this phenomenon, we theoretically analyze the kinetics of seed-dependent amyloid formation. The results suggest that ultrasonic cavitation induces the formation of a dead-end complex between serum albumin and α-Syn monomers, which can reduce false positives by suppressing seed-independent amyloid formation. These findings demonstrate ultrasonication as a powerful tool for the sensitive detection of α-Syn seed in clinical diagnostics.