A sequential photodynamic-antioxidation therapy against Alzheimer's β-amyloid enabled by a dual‑carbon dots nanomotor

Abnormal accumulation of β-amyloid protein (Aβ) in the brain is considered as the primary hallmark of Alzheimer's disease (AD). Beyond inducing neuronal metabolic disorders and apoptosis, Aβ activates oxidative stress pathways, thereby exacerbating reactive oxygen species (ROS) toxicity. Therefore, the design of effective multi-target synergistic therapeutics targeting Aβ and excessive ROS has emerged as a critical strategy for AD prevention and treatment. Herein, we propose a "Sequential Photodynamic-Antioxidation Therapy (SPAT)" against Alzheimer's Aβ, and the SPAT strategy is enabled by the design of a sub-10nm dual‑carbon dots Janus composite (SeRCD) composed of a newly designed and synthesized selenium-doped high-efficiency antioxidant carbon dot (SeCD) and a previously reported near-infrared (NIR) carbon dot (RCD) possessing both thermogenic and photodynamic functionalities. The thermogenic property of RCD in SeRCD endows the Janus composite with photo-propelled autonomous motion powered by "self-thermophoretic force" under NIR irradiation. Thus, SeRCD shows potent inhibition of Aβ fibrillization at low concentrations (0.5 to 5 μg/mL) via photooxygenation and the nanomotor effect under NIR irradiation for only 10 min. Under the subsequent NIR-off condition, SeCD in SeRCD effectively mitigates the oxidative damage to cells by scavenging ROS. Thus, the lifespan of AD nematodes is prolonged by the SPAT strategy from 12 to 19 d at 2 μg/mL. The results collectively demonstrate the effectiveness of the dual-CDs composite design and great potential of the SPAT strategy for application in fighting against AD.