α-Synuclein Oligomer Detection with Aptamer Switch on Reduced Graphene Oxide Electrode

Abstract

Protein aggregation of alpha-synuclein (α-Syn) is implicated in Parkinson’s disease (PD), and, thus, α-Syn aggregates are a potentially promising candidate biomarker for PD diagnosis. Here, we describe a simple and sensitive electrochemical sensor to monitor the aggregation of α-Syn for early PD diagnosis. The sensor utilizes methylene blue (MB)-tagged aptamer (Apt) adsorbed on electrochemically reduced graphene oxide (ERGO) by π–π stacking. The binding of α-Syn oligomer to the Apt induces desorption of the Apt from the ERGO surface, which leads to the electrochemical signal change. The resulting sensor allowed the highly sensitive and selective detection of α-Syn oligomer according to the voltammetric change. Under optimized conditions, the linear range of detection was observed to be from 1 fM to 1 nM of the α-Syn oligomer and the limit of detection (LOD) was estimated to be 0.64 fM based on S/N = 3. The sensor also showed good reproducibility and stability, enabling real sample analysis of the α-Syn oligomer in human blood serum. With its ultrasensitivity and good performance for α-Syn oligomer detection, the sensor provides one promising tool for the early diagnosis of PD.

Alpha-Synuclein in the Gastrointestinal Tract as a Potential Biomarker for Early Detection of Parkinson’s Disease

“…Nanoparticle-based methodologies, including sensor-based techniques, could also represent an interesting approach to early diagnosis of PD [ 123 , 124 , 125 ]. These methodologies are able to target the α-Syn oligomers with very high sensitivity up to the level of 1 fM [ 123 ]. In most cases, these methodologies have been used on recombinant systems, but information on the validation of these methodologies on human samples, such as human serum, is gradually emerging.…”

Comparison of Different Platform Immunoassays for the Measurement of Plasma Alpha-Synuclein in Parkinson’s Disease Patients

“…However, measurement of alpha-synuclein is complicated as it can exist as a monomer, in higher order complexes (e.g., tetramer), in post translationally modified forms (e.g., phosphorylated, nitrosylated), and in aggregated pathogenic forms (oligomers of different sizes and fibrils) [3][4][5][6]. While there is merit in detecting different forms of alphasynuclein, assays to detect the post translationally modified and aggregated forms of alpha-synuclein in human biofluids remain largely in development (e.g., [7][8][9][10][11][12][13][14][15][16][17][18][19][20]), and/or have not yet been cross-validated by multiple research groups.…”

A FRET-based aptasensor for the detection of α-synuclein oligomers as biomarkers of Parkinson's disease

“…In addition, the colorimetric sensor performance in a serum sample was reported to be unsuccessful. The developed electrochemical biosensors 14,15 have also shown an acceptable LOD. However, they are mostly complex and time consuming due to the need for electrode functionalization.…”

“…9 The other instrumental methods of α-syn oligomer detection, such as capillary electrophoresis, 10 mass spectrometry, 11 and nuclear magnetic resonance spectroscopy 12 are generally expensive, complex, and time-consuming and require sample preparation and skilled operators. In recent years, several colorimetric, surface plasmon resonance, 13 electrochemical 14,15 and electrochemiluminescence 16 biosensors have been reported to detect α-syn oligomers, many of which have shortcomings such as low sensitivity or specificity.…”