Sample preparation for direct nanopore based protein identification via tryptic peptide recognition

Abstract

Rapid, cost-efficient and miniaturized protein analysis is essential for point-of-care clinical diagnostics. Nanopores offer a promising alternative to mass spectrometry, offering high-resolution, single-molecule sensing with a minimal footprint. However, peptide-level protein identification remains challenging due to difficulties in assigning nanopore signals to peptide sequences and the incompatibility of conventional proteolysis workflows with nanopore sensing. Here we integrate a single-pot, solid-phase-enhanced sample preparation (SP3) workflow with nanopore sensing. The SP3 protocol decouples proteolysis from interfering components via magnetic bead cleanup, yielding a digest compatible with nanopore sensing. As a proof of concept, tryptic digests of myelin basic protein measured with an engineered aerolysin variant (AeL-R220S) generated a reproducible five-peak peptide fingerprint. Cross-validation against a synthetic peptide library and LC-MS/MS enabled reference-based assignment of blockade signatures to four MBP-derived peptides. This approach establishes SP3 as a sample-preparation workflow for nanopore sensing, paving the way for label-free identification and characterization of protein targets.