Alternating Magnetic Field-Promoted Nanoparticle Mixing: The On-Chip Immunocapture of Serum Neuronal Exosomes for Parkinson's Disease Diagnostics

The analysis of cargo proteins in exosome subpopulationshas considerablevalue in diagnostics but a translatable impact has been limited bylengthy or complex exosome extraction protocols. We describe hereina scalable, fast, and low-cost exosome extraction using an alternating(AC) magnetic field to support the dynamic mixing of antibody-coatedmagnetic beads (MBs) with serum samples within 3D-printed microfluidicchips. Zwitterionic polymer-coated MBs are, specifically, magneticallyagitated and support ultraclean exosome capture efficiencies >70%from <50 & mu;L of neat serum in 30 min. Applied herein to theimmunocapture of neuronal exosomes using anti-L1CAM antibodies, priorto the array-based assaying of & alpha;-synuclein (& alpha;-syn) contentby a standard duplex electrochemical sandwich ELISA, sub pg/mL detectionwas possible with an excellent coefficient of variation and a sample-to-answertime of & SIM;75 min. The high performance and semiautomation ofthis approach hold promise in underpinning low-cost Parkinson'sdisease diagnostics and is of value in exosomal biomarker analysesmore generally.

Automated summary

We present a scalable, fast, and low-cost method for extracting cargo proteins from exosome subpopulations using an alternating (AC) magnetic field to facilitate the mixing of antibody-coated magnetic beads (MBs) with serum samples. By applying this method, we were able to achieve high capture efficiencies of >70% from <50 μL of neat serum in just 30 minutes. This approach, when combined with array-based assaying and a standard duplex electrochemical sandwich ELISA, enabled the detection of sub pg/mL levels of α-synuclein content with excellent precision and a sample-to-answer time of approximately 75 minutes. The high performance and semi-automation of this method hold promise for low-cost Parkinson's disease diagnostics and exosomal biomarker analyses.