Measuring Blood Plasma Glutamine Levels Using a Nanopore‐Based Sensor

Measuring blood glutamine (GLN) levels is valuable for managing urea cycle disorders. Currently, patients visit the hospital to have their GLN levels checked using analytical techniques that, despite being highly accurate and reliable, lead to long waiting times and delay clinical decisions. A point-of-care device would enable patients to monitor GLN levels at home, allowing for greater control over the condition. Here, we made use of a highly sensitive GLN biosensor system based on dodecameric Cytolysin A variant AS (ClyA-AS) nanopore coupled with the GLN-specific protein, the substrate-binding domain 2 (SBD2). Measurements are performed on a single ClyA-AS nanopore embedded into an artificial lipid bilayer, where the application of a small voltage generates ionic currents that report on the binding and unbinding of GLN (added in the trans side of ClyA-AS) to SBD2 (added in cis). We demonstrate that the ClyA-AS and SBD2 biosensor pair can quantify GLN levels in patients' blood plasma. To facilitate the use of this sensor in clinical and point-of-care settings, we also developed a dedicated algorithm that accelerates signal processing and data analysis. Together, these advances represent a significant step toward a point-of-care device for GLN monitoring, both at the hospital and home-care levels.