A machine learning-assisted Cu-MOF/OPD/RB triple-emission ratiometric fluorescence sensing platform for the detection and discrimination of glutathione

Abstract

Herein, a machine learning-assisted Cu-MOF/OPD/RB triple-emission ratiometric fluorescence sensing platform has been developed for the highly sensitive and selective detection of glutathione (GSH). The bifunctional Cu-MOF serves as the core, exhibiting intrinsic blue fluorescence at 450 nm and peroxidase-like activity to catalyze the oxidation of o-phenylenediamine (OPD) into fluorescent DAP (545 nm) in the presence of H₂O₂. Rhodamine B (RB) is further introduced to provide red emission at 580 nm. DAP quenches the fluorescence of the Cu-MOF through an inner filter effect (IFE) while simultaneously enhancing the emission of RB via fluorescence resonance energy transfer (FRET), thereby establishing an interconnected three-channel ratiometric sensing system (F₄₅₀, F₅₄₅, F₅₈₀). GSH inhibits the peroxidase activity of the Cu-MOF via strong chelation of Cu²⁺ and also directly reduces DAP through its reducing properties, collectively suppressing the generation of DAP. Consequently, F₅₄₅ and F₅₈₀ decrease, while F₄₅₀ recovers due to the weakened IFE. A ratiometric detection method was established based on the signal F₄₅₀/(F₅₄₅ + F₅₈₀), achieving a detection limit of 0.27 μM for GSH. The method exhibited satisfactory recoveries of 90.0%–105.0% with RSD ≤ 5.8% in real samples. Moreover, machine learning models (PCA, K-means) use the three fluorescence intensities as multi-dimensional inputs, allowing accurate GSH quantification and effective discrimination from interfering reducing agents, significantly enhancing selectivity in complex matrices.