Smartphone-assisted colorimetric detection of glutathione in food and pharmaceutical samples using MIL-88A(Fe)

Metal-organic frameworks (MOFs) have risen to prominence due to their unique structural features, including high porosity and tunable surface chemistry. As nanozymes, the MOFs replicate the catalytic activity of natural enzymes, thereby offering stability under diverse conditions and heightened efficiency. Glutathione (GSH) is a vital intracellular antioxidant and disease biomarker for cancer and neurodegenerative disorders. In this study, the intrinsic-oxidase activity of MIL-88A(Fe) was explored to develop a naked-eye-based colorimetric sensor for the detection of GSH. The 3,3',5,5',-tetramethyl benzidine (TMB) substrate was oxidized by MIL-88A(Fe), leading to the formation ofblue-colored oxidized TMB. The addition of GSH resultsin the reduction of oxidized TMB, causing the blue color to fade and a decrease in absorbance at 652 nm. Under optimal conditions, the developed sensor has a good linear relationship with GSH concentrations ranging from 0-40 μM with a detection limit of 150 nM. The developed methodwas successfully used to determine GSH accurately in real food and pharmaceutical samples. Further, the sensor demonstrated satisfactory performance for smartphone-based GSH detection on a paper-based assay. This work demonstrates the rapid, inexpensive, and ultrasensitive detection of GSH, opening new avenues for additional food quality and pharmaceuticalmonitoring.