Integrated Workflow for the Quantification of Urinary Exosomes Isolated via C–CP Fiber Tips with Lanthanide Chelation Labeling and ICP-MS Detection

Exosomes, a subset of extracellular vesicles (EVs) ranging in size from 30 to 150 nm, are important, emergent tools in clinical diagnostics and biochemical studies. Exosomes are excreted from cells and participate in many biological processes, including intercellular communication and disease propagation. Challenges in quantification stem from problems in isolating pure and morphologically intact exosomes from complex biomatrices. This study presents a novel method for exosome quantification using capillary channeled polymer (C-CP) fiber spin-down tips for isolation and removal of unbound metal tags, ytterbium chloride (YbCl₃) for labeling, and inductively coupled plasma mass spectrometry (ICP-MS) for quantification. Use of polyester (PET) C-CP fiber spin-down tips enables a rapid and cost-effective exosome isolation that preserves the morphological integrity of the exosomes. A well-known chelation reaction between trivalent lanthanide ions (Yb³⁺ here) and phosphate groups in the exosome phospholipid bilayer allows for sensitive quantification, with labeling optimized at 10 mM YbCl₃ for 30 min at 37 °C. Results showed a linear relationship (R² > 0.95) between Yb ICP-MS response and exosome particle counts, with a detection limit of 1.16 × 10² exosomes mL^-1. This integrated workflow has the potential to be combined with targeted biomarker labeling as a comprehensive quantification and identification technique for clinical diagnostics.