Sensitive Immunosensing of α-synuclein Protein in Human Plasma Samples Using Gold Nanoparticles Conjugated with Graphene: an Innovative Immuno-platform Towards Early Stage Identification of Parkinson's Disease Using Point of Care (POC) Analysis

Parkinson's disease (PD) or simply Parkinson's is a long-term degenerative disorder of the central nervous system, which mainly affects the motor system. Consequently, the detection and quantification of related biomarkers play vital roles in the early-stage diagnosis of PD. In the present study, an innovative electrochemical immunosensor based on gold nanoparticle-modified graphene towards bioconjugation with biotinylated antibody (bioreceptor) was developed for the ultra-sensitive and specific monitoring of the alpha-synuclein (α-synuclein) protein. The synergistic effects between the gold nanoparticles (AuNPs) and graphene drastically enhanced the electrochemical activity of the resulting materials. The enhanced conductivity of the substrate together with the increase in its surface area improved the sensitivity and lowered the detection limit of the capture layer. For the first time, the α-synuclein protein was measured in human plasma samples using bioconjugated AuNP-Gr bioconjugated specific antibody with an acceptable linear range of 4 to 128 ng mL and a lower limit of quantification (LLOQ) of 4 ng mL. Accordingly, it is expected that this diagnostic method may be produced in the near future for clinical applications and high-throughput screening of PD using point of care (POC) analysis.