N-Amino Peptide-Graphene Quantum Dot Loaded Small Extracellular Vesicles for Targeted Therapy of Tauopathies

Tauopathies, a group of neurodegenerative disorders, are characterized by the abnormal aggregation of tau proteins into neurofibrillary tangles, driving synaptic dysfunction, neuronal loss, and disease progression through tau aggregate propagation. Graphene quantum dots (GQDs) functionalized with D-cysteine (D-GQDs) have shown promise in inhibiting tau aggregation and transmission via π-π stacking and electrostatic interactions with tau proteins. However, the nonspecific binding of GQDs to various proteins in the physiological environment, such as serum albumin, limits their clinical translation. In this study, the aim is to enhance the specificity of D-GQDs toward tau protein by incorporating a tau-targeting N-amino peptide, mxyl-NAP2. The mxyl-NAP2/D-GQD complex demonstrates improved selectivity for tau protein over serum albumin, effectively enhancing the inhibition of tau aggregation. To further minimize off-target effects and optimize therapeutic delivery, the mxyl-NAP2/D-GQD complex is loaded into small extracellular vesicles (sEVs), followed by functionalization of sEVs with neuron-targeting ligand, rabies viral glycoprotein peptides. This strategy not only reduces off-target effects, but also enhances uptake by neuron cells, which further improves inhibition of tau transmission between neurons. The results indicate that mxyl-NAP2/D-GQD-sEVs hold great promise for overcoming the off-target limitations of D-GQDs and advancing the development of precision therapeutics for neurodegenerative diseases.