Selective Nanopore Detection of Monoamine Oxidase A and B in a Single Sample

Abstract Monoamine oxidases A and B (MAO‐A and MAO‐B) are key enzymes involved in neurotransmitter metabolism and are critical biomarkers for neurodegenerative and psychiatric disorders. Here, we present a highly sensitive nanopore‐based method for the selective detection and quantification of MAO‐A and MAO‐B using specifically designed peptide probes. These probes undergo enzyme‐specific oxidation, generating distinct nanopore translocation signatures that enable precise identification. Our method achieves picomolar‐level detection, outperforming conventional assays such as ELISA. Importantly, we demonstrate its applicability in complex biological samples, including cell lysates (SH‐SY5Y and HepG2) and mouse brain and liver tissues, with results strongly correlating with ELISA. The ability to selectively detect both enzymes within a single sample highlights its advantage in studying enzyme interplay in biological systems. This label‐free, real‐time approach offers a powerful tool for biomedical research, disease diagnostics, and drug screening, with potential for expanding to other clinically relevant enzymes.