Magnetic Enrichment of Immuno-Specific Extracellular Vesicles for Mass Spectrometry Using Biofilm-Derived Iron Oxide Nanowires

Abstract

AbstractImmuno-specific enrichment of extracellular vesicles (EVs) originating from specific cells/tissues is a promising source of information towards improving insights into cellular pathways underpinning various pathologies and developing novel non-invasive diagnostic methods. Enrichment is an important aspect in mass spectrometry-based analyses of EVs. Herein, we report a protocol for immuno-magnetic enrichment of subtype specific EVs and their subsequent processing for mass spectrometry. Specifically, we conjugated placental alkaline phosphatase (PLAP) antibodies to magnetic iron oxide nanowires (NWs) derived from bacterial biofilms and demonstrated the utility of this approach by enriching placental specific EVs (containing PLAP) from cell culture media. We demonstrate efficient PLAP+ve EV enrichment for both NW-PLAP and Dynabeads™-PLAP, with PLAP protein recovery (83.7±8.9% and 83.2±5.9%, respectively), high particle-to-protein ratio (7.5±0.7×109 and 7.1 ± 1.2×109, respectively), and low non-specific binding of non-target EVs (7±3.2% and 5.4±2.2%, respectively). Furthermore, our optimized EV enrichment and processing approach identified 2518 and 2545 protein groups with mass spectrometry for NW-PLAP and Dynabead™-PLAP, respectively, with excellent reproducibility (Pearson correlation 0.986 and 0.988). The proposed immuno-specific EVs enrichment and liquid chromatography-tandem mass spectrometry method using naturally occurring iron oxide magnetic NWs or gold-standard Dynabeads™ enables high-quality EV proteomic studies.