The Detection of Toxic Amyloid-β Fibril Fragments Through a Surface Plasmon Resonance Immunoassay

Amyloid-β1–42 (Aβ42) forms highly stable and insoluble fibrillar structures, representingthe principal components of the amyloid plaques present in the brain of Alzheimer’s disease (AD)patients. The involvement of Aβ42 in AD-associated neurodegeneration has also been demonstrated,in particular for smaller and soluble aggregates (oligomers). Based on these findings and on geneticevidence, Aβ42 aggregates are considered key players in the pathogenesis of AD and targets for noveltherapies. Different approaches are currently used to detect the various aggregation states of Aβpeptide, including spectrophotometric methods, imaging techniques, and immunoassays, but all ofthese have specific limitations. To overcome them, we have recently exploited the peculiar propertiesof surface plasmon resonance (SPR) to develop an immunoassay capable of selectively detectingmonomers and oligomers, discriminating them also from bigger fibrils in a mixture of differentaggregated species, without any manipulation of the solution. In the present study, we extendedthese previous studies, showing that the SPR-based immunoassay makes it possible to unveil thefibril fragmentation induced mechanically, a result difficult to be conveniently and reliably assessedwith other approaches. Moreover, we show that SPR-recognized fibril fragments are more toxic thanthe larger fibrillar structures, suggesting the relevance of the proposed SPR-based immunoassayβ淀粉样蛋白1-42（Amyloid-β1–42, Aβ42）可形成高度稳定且不溶性的纤维状结构，是阿尔茨海默病（Alzheimer’s disease, AD）患者大脑内淀粉样斑块的核心组成成分。已有研究证实Aβ42参与了AD相关的神经退行性病理过程，尤其是其较小的可溶性聚集产物（寡聚体）。基于上述发现与遗传学证据，Aβ42聚集物被认为是AD发病机制中的关键致病因子，同时也是新型治疗策略的潜在靶点。当前学界已开发多种手段用于检测Aβ肽的不同聚集状态，包括分光光度法、成像技术与免疫测定法，但此类方法均存在特定局限性。为克服上述局限，本研究团队近期利用表面等离子体共振（surface plasmon resonance, SPR）的独特特性，开发出一种免疫测定方法，可在无需对溶液进行任何操作的前提下，选择性检测单体与寡聚体，并能在多种聚集形式共存的混合体系中，将二者与更大的纤维结构区分开来。本研究在既往工作基础上进行了拓展，证实基于SPR的免疫测定法可揭示机械诱导的纤维碎裂过程——这一结果难以通过其他方法便捷且可靠地完成评估。此外，本研究还发现，经SPR识别的纤维片段相较于更大的纤维结构具有更强的毒性，这凸显了本研究所提出的基于SPR的免疫测定法的应用价值。