Intranasal L-DOPA/TPP-Engineered Extracellular Vesicles Deliver Icariin to Ameliorate Mitochondrial Dysfunction with Associated Sphingolipid Remodeling in Alzheimer’s Disease Models

Alzheimer’s disease (AD) is associated with mitochondrial dysfunction, oxidative stress, and disrupted lipid homeostasis, but the therapeutic translation of mitochondrial-protective agents remains limited by inefficient brain delivery, insufficient neuronal selectivity, and poor subcellular precision. Here, we developed an intranasal extracellular vesicle formulation (L-DOPA/TPP-EV-ICA) by loading icariin (ICA) into mesenchymal stem cell-derived extracellular vesicles and post-inserting DSPE-PEG-Levodopa and TPP-PEG-PE to enhance nasal environment, neuronal association, and mitochondria-associated intracellular enrichment. The engineered vesicles retained EV-like morphology, showed measurable ICA encapsulation, and maintained colloidal stability under the tested storage and simulated nasal conditions. In a human nasal epithelial Transwell model, L-DOPA/TPP-EV-ICA showed greater neuronal uptake than unmodified EVs without detectable disruption of epithelial barrier integrity and exhibited preferential colocalization with mitochondria-associated structures after cellular internalization. In Aβ-injured neuronal cells, L-DOPA/TPP-EV-ICA treatment reduced mitochondrial oxidative stress and mPTP opening, improved membrane potential, and enhanced ATP production and redox-related parameters. Following intranasal administration, the engineered formulation generated stronger and more persistent brain-associated fluorescence and showed preferential association with NeuN-positive cells. In APP/PS1 mice, treatment improved cognitive performance, and attenuated histopathological and mitochondrial abnormalities. Integrated proteomic, metabolomic analyses, and protein-level analyses further identified treatment-associated alterations in sphingolipid-related pathways. These findings support L-DOPA/TPP-EV-ICA as a promising preclinical intranasal EV platform for improving mitochondrial function and modulating sphingolipid-associated alterations in AD-related models.