Abstract
The egress of α-synuclein in neuronally derived exosomes predates the clinical presentation of Parkinson’s disease (PD), offering a means of developing a predictive or prognostic test. Here, we report the reagentless impedimetric assay of two internal exosome markers (α-synuclein and syntenin-1) from neuronal exosomes. Exosomes were efficiently extracted from patient sera using anti-L1CAM conjugated zwitterionic polymer-modified magnetic beads prior to lysis and analyzed by electrochemical impedance spectroscopy. The quantification of α-synuclein level across 40 clinical samples resolved statistically significant differences between PD patients and healthy controls (HC).
Highlights
We report the reagentless impedimetric assay of two internal exosome markers (α-synuclein and syntenin-1) from neuronal exosomes
We further demonstrated that pCBMA@Fe3O4 MBs, unlike commercially available carboxylate MBs, exhibited good antifouling properties when incubated with soluble recombinant α-synuclein, irrespective of the antibody used (anti-L1CAM or anti-HA as shown in Successful polymerization of pCBMA on beads was resolved by infrared attenuated total reflection spectroscopy (IR-ATR) (Figure S1A).[32,33]
To further assess the reliability of the electrochemical assay in measuring neuronal exosome-associated α-Syn and Synt-1, we cross referenced the same samples with the electrochemiluminescence kit platform (Figure S9) where the difference between Parkinson’s disease (PD) vs healthy controls (HC) was observed (p = 1.48 × 10−5 albeit with 500% greater serum volume)
Summary
Anti-L1CAM-modified polymer brush-coated MBs enable the selective immunocapture of neuronal exosome subpopulations from 100 μL of serum prior to a sensitive (sub pg/mL) and reagentless impedimetric assay. The cleanliness of the initial isolation enables subsequent electroanalyses to be performed on a standard and readily scalable monolayer film from much lower levels of serum than required for electrochemiluminescence or ELISA. These analyses further confirm the value of exosomal of α-Syn as a relevant biomarker in PD.[4] The study offers a solution for effectively verifying biomarkers in clinical translation and lays a foundation for on-chip integration of immunocapture and reagentless analysis of exosome biomarkers in a scalable manner. The manuscript was written with contributions from all authors.
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