Rational Design, Synthesis, and Evaluation of Rofecoxib-Based Photosensitizers for the NIR Imaging and Photo-Oxidization of Aβ Aggregates

The photo-oxidation of amyloid-β (Aβ) protein catalyzed by Aβ-targeting photosensitizers shows high potential in treating Alzheimer's disease (AD). Herein, we report the first example of photosensitizers based on the rofecoxib scaffold, in which rational introduction of the electron-absorbing pyridinium/quinolinium moiety to the skeleton of rofecoxib could not only extend the absorption and emission wavelengths but also increase the efficiency of singlet oxygen (¹O₂) production. The emission wavelengths of <b>R-S-MP</b>, <b>R-S-MC</b>, and <b>R-S-MQ</b> are red-shifted to 860 nm, which might benefit the NIR imaging of Aβ aggregates with low photoscattering and autofluorescence. In addition, <b>R-S-MP</b> can identify Aβ plaques in brain sections of AD mice and detect abnormal viscosity environments, facilitating the pathological study of Alzheimer's disease. Most importantly, upon complexation with Aβ plaques, <b>R-S-MP</b> and <b>R-S-MC</b> could produce high singlet oxygen (¹O₂) under light irradiation, which can achieve the specific photo-oxidation of Aβ protein. Our optimized photosensitizers could change the conformation of β-rich Aβ protein and enhance its clearance through the lysosomal pathway, leading to the reduction of the Aβ-mediated neurotoxicity. All these excellent characteristics of our dual-functional photosensitizers for simultaneous imaging and photo-oxidation of Aβ aggregates suggest their promising prospects in pathological research in AD.