Targeting Membrane Lipid and Curvature Signatures for Neuronal Exosome Capture and Protein Profiling as a Liquid Biopsy for Cognitive Impairment.

Selective isolation and analysis of brain-derived exosomes are essential for understanding and clinical management of neurodegeneration diseases. Herein, inspired by the unique lipidomic features of the central nervous system and lipid packing signature of exosomal membranes, we report a high-performance exosome capture platform, Exo-RTrap, developed through screening of the molecular interactions between an arginine-rich peptide (R9) and main lipids. Different from conventional view of nonspecific electrostatic association, we demonstrate highly selective and high-affinity binding of R9 toward phosphatidylserine (PS) over other anionic lipids, accompanied by spontaneous assembly into nanoscale vesicular complexes. Notably, R9 exhibits 370-fold stronger affinity for PS-containing liposomes than PS-free ones and recognizes membrane curvature in a PS-dependent manner, with sensitivity regulated by PS lateral density. Guided by these mechanistic insights, Exo-RTrap with dual-mode recognition coupling PS targeting with curvature responsiveness enabled rapid and selective isolation of exosomes from complex medium and biofluids, with purity and antifouling ability exceeding ultracentrifugation and precipitation methods. The capability of Exo-RTrap to selectively enrich disease-relevant neuronal exosomes was demonstrated by its accurate discrimination of serum samples from patients with Alzheimer's disease and mild cognitive impairment, whereas exosomes isolated by ultracentrifugation failed to achieve comparable performance. Moreover, integration with mass spectrometry-based proteomics further identified differentially expressed proteins as potential biomarkers for staging cognitive impairment. By defining the molecular rules governing R9-lipid interactions, this work presents a promising peptide-based exosome isolation platform for early detection and monitoring of neurodegenerative disorders.