Polydopamine nanoparticles restore cognition via targeted dopamine delivery and septo-hippocampal cholinergic activation.

Abstract

Altered dopamine (DA) neurotransmission in key brain circuits underlies cognitive deficits across psychiatric and neurological disorders by disrupting working memory, attention, and executive function. Here, we introduce a novel, carrier-free nanotherapeutic approach using polydopamine nanoparticles (PDA NPs)-synthesized via oxidative self-polymerization of DA hydrochloride-for targeted DA supplementation and cognitive rescue. Uniform, spherical PDA NPs (~250 nm) exhibit excellent biocompatibility and cross the blood-brain barrier via endocytosis. In acidic environments, they degrade to release DA, which is internalized by endothelial and neuronal cells and subsequently converted into downstream catecholamines. In a mouse model of lipopolysaccharide-induced cognitive impairment, PDA NP treatment fully restored performance in Y-maze and novel-object recognition tests. Biochemical analyses showed that short-term administration elevated hippocampal DA, norepinephrine, and tyrosine, while prolonged treatment markedly increased acetylcholine levels. This long-term cholinergic enhancement was mediated by activation of septo-hippocampal projections via DA D2 receptor signaling in the medial septal nucleus. Together, these results establish PDA NPs as an effective, carrier-free platform for targeted DA delivery that not only replenishes catecholamines but also engages cholinergic circuits to ameliorate cognitive impairments.