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Electrochemical Strategy for Analyzing the Co-evolution of Cu2+ and •OH Levels at Earlier Stages of Transgenic AD Mice.

As more researchers have acknowledged that the aggregation of amyloid beta peptides (Aβ) might only be a pathological phenomenon that appears during the course of Alzheimer's disease (AD), it is therefore of great significance to have a preclinical or an early clinical diagnosis. Cu2+ dyshomeostasis and oxidative stress, such as hydroxyl radical (·OH), are found to be associated with peptide aggregations. Still we don't know, however, that how the levels of Cu2+ and ·OH are altered in brains before massive Aβ plaques appear. Herein, we demonstrated the design and application of a sensitive electrochemical sensor to monitor Cu2+ and ·OH simultaneously in one system without obvious cross-talk. The electrode was fabricated using black phosphorus loaded Au nanoparticles (BP-Au), which was then sequentially linked with DNA1, DNA2-labled Au nanoparticles (Au-DNA2) and methylene blue (MB). Cu2+ was firstly recognized and captured onto sensor by BP with a high selectivity and then produced a reduction current around -0.01 V. The ·OH quantification was established on the cleavage of the hybrid structure between DNA1 and BP-Au upon the appearance of ·OH in the PBS, leading to the depletion of the voltammetric response of MB nearby -0.25 V. Good linear correlations were obtained over concentrations of 0.5 ~ 127.5 μM for Cu2+ and 0.5 ~ 96.0 μM for ·OH, respectively. Most importantly, the developed sensor was successfully applied to track the variations of the two species in brain tissues from APP/PS1transgenic AD mice at earlier stages before massive Aβ plaques appeared.