Targeted Raman Visualization and Mitigation of α‐Synuclein Amyloidogenesis in Living Zebrafish by a Nanobody‐Decorated Polydiacetylene

Abstract α‐Synuclein (α‐Syn) amyloidogenesis is considered a promising diagnostic marker and therapeutic target for Parkinson's disease (PD). Simultaneously visualizing and mitigating α‐Syn amyloidogenesis are essential for future PD theranostics, yet they continue to pose an insurmountable challenge. This study have herein developed a nanobody‐decorated polydiacetylene to approach a straightforward solution. Grafting α‐Syn61‐95 segment into the third complementary determining region of a parent nanobody generates an engineered nanobody X30 that can bind with α‐Syn and prevent its amyloidogenesis through homotypic interaction. It next use X30 to decorate poly(deca‐4,6‐diynedioic acid) (PDDA), a polydiacetylene with an ultrastrong alkyne Raman signal (2120 cm ⁻¹ ) in the cellular silent region, to create an α‐Syn targeting Raman probe PX30. The binding affinity between X30 and α‐Syn can be further boosted for over 150 times attributed to the rigidity of PDDA backbone and the multivalent effect. Therefore, PX30 not only enables real‐time Raman visualization of α‐Syn amyloidogenesis with a high signal‐to‐noise ratio in living zebrafish, but also alleviates amyloidogenesis‐mediated damage to zebrafish embryos by effectively inhibiting α‐Syn amyloidogenesis at low stoichiometric concentrations and scavenging pathologic reactive oxygen species.