Computationally guided engineering of an aptamer–gold nanoparticle aptasensor for ultrasensitive detection of α-synuclein in biological matrices

Early, reliable detection of α-synuclein (αSN) is critical for Parkinson's disease diagnosis, yet antibody-based assays remain limited by sensitivity, matrix effects, and cost. We report a label-free aptamer–gold nanoparticle nanobiosensor (G 12 Apt@AuNP) for non-invasive αSN detection in saliva. Molecular docking identified F5R1 as the aptamer with the most favorable predicted binding affinity; a dodeca-guanine (G12) was appended to provide colloidal stabilization and to control conjugation and orientation on the AuNP surface. Interaction with αSN monomers, oligomers, and fibrils produced a concentration-dependent plasmonic red-shift arising from αSN-induced nanoparticle aggregation. Conditions were optimized by Taguchi design and ANOVA. Across 8 pM–8 μM, the platform achieved an 8 pM detection limit and a 0.8 nM–0.8 μM linear range for 24 h aggregated αSN, comparing favorably with reported label-free optical aptasensors. It showed high selectivity against related proteins and detectable responses in spiked saliva at 4 nM, supporting development toward clinical synucleinopathy detection.