Gelsolin Encountering Ag Nanorods/Triangles: An Aggregation-Based Colorimetric Sensor Array for in Vivo Monitoring the Cerebrospinal Aβ₄₂% as an Indicator of Cd²⁺Exposure-Related Alzheimer's Disease Pathogenesis

Nowadays, the environmental risk factors for Alzheimer's disease (AD) have received widespread attention. Two major amyloid-β peptide (Aβ) variants, Aβ42 and Aβ40, play a pivotal role in the etiology of AD and the concentration ratio of which (i.e., Aβ42%) has been suggested to be the superior biomarker for AD. In this study, an "aggregation-based colorimetric sensor array"for the simultaneous identification and detection of Aβ40 and Aβ42 with structural similarity was established based on gelsolin-modified silver nanotriangles (Ag NTs) and silver nanorods (Ag NRs). Different aggregation behaviors of gelsolin-modified Ag NTs and Ag NRs in the presence of Aβ42 and Aβ40 resulted in different color and spectral changes, which could be quantitatively analyzed in terms of unique spectral patterns by principal component analysis. With the colorimetric sensor array employed here, the fluctuation of Aβ42% in different brain regions of rats exposed to Cd2+ could be directly monitored. The downward trend of Aβ42% accompanied by variations of other biochemical indicators suggested that subchronic Cd2+ exposure possibly triggered the onset of AD through the intervention of lipid peroxidation pathway. Furthermore, in vivo monitoring the downtrend of Aβ42% in cerebrospinal fluid (CSF) could also be realized, which offers a great opportunity for early diagnosis and treatment of AD that may be induced by environmental factors with CSF Aβ42% as a reliable indicator.