Fluorescence‐Based Detection of Methionine for Noninvasive Cancer Diagnosis Using Cu–Sn Bimetallic Nanoclusters

Methionine is an essential sulfur-containing amino acid that plays a pivotal role in cancer biology due to its abnormal metabolism in malignant cells. Elevated methionine levels serve as potential biomarkers for various cancers, highlighting their diagnostic significance. This study presents a bimetallic sensing platform using L-cysteine-capped copper-tin nanoclusters (Cu-SnNCs) for the selective and sensitive detection of methionine. The Cu-SnNCs are synthesized via a one-pot hydrothermal process, exhibiting strong blue fluorescence, high stability, and significant optical properties. Fe³⁺ is employed as a quencher, leveraging its paramagnetic nature to suppress fluorescence, which is subsequently restored upon the addition of methionine. The sensing mechanism demonstrates a linear response over a methionine concentration range of 0.18-1.62 mm, with a detection limit of 1.69 μm. The probe's potential is further validated with a preliminary paper strip test for detecting methionine in biological samples. These findings underscore the utility of Cu-SnNCs as a noninvasive, economical diagnostic tool for cancer detection and screening.