A de novo strategy for the development of a ZnII–organic framework based luminescent “switch-on” assay for size-exclusive sensitization of the oxidised form of glutathione (GSSG) over the reduced form (GSH): insights into the sensing mechanism through DFT†
The ratio of oxidized L-glutathione (GSSG) to reduced L-glutathione (GSH) plays a key role as a biomarker for monitoring cellular health thus fuelling extensive ground-breaking research towards the development of sensory receptors for continuous monitoring of glutathione concentration. The detection of GSH is well documented; however, studies on the oxidized form, i.e., GSSG, are very scanty in the literature due to their functional similarity. In this context, metal–organic frameworks (MOFs) provide rationalized structure–performance synergies to fabricate smart chemoprobes. Herein, we present robust and non-interpenetrated ZnII–MOF (designated as Zn-CMERI) exemplifying a unique scaffold for efficient optical sensitization of biohazards such as GSSG through a fluorescence “switch-off–on” process with a detection limit of 20.8 ppb (R = 0.98 and Kec = 84.12) with very short response time (∼12 s). More interestingly, as a recyclable chemoprobe Zn-CMERI can be exploited for detecting GSSG in complex biological matrices (Recovery % = 95.5–108.6), which in turn helps in detecting patients with uremic disease. The role of SBUs has been validated from in-depth DFT studies, which collectively supports the importance of the de novo strategy of incorporating O, N-sites for non-covalent host–guest interactions in a confined zone in supramolecular chemistry for detecting mercapto biomolecules. Additionally, the host–guest interaction through a “switch-off–on” assay may be utilised for fabricating molecular logic gate circuitry in relevance to MOFtronics applications.