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

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.