Switch-on hydrogel biosensor based on self-assembly Mn-doped ZnS QDs and cellulose nanofibrils for glutathione detection

Herein, a switch-on hydrogel biosensor based on self-assembled Mn-doped ZnS quantum dots (QDs) in cellulose nanofibrils (CNFs) has been developed for rapid and selective sensing of glutathione (GSH) in serum sample. The biosensor has successfully integrated Mn:ZnS QDs with high quantum yield, high dispersion stability and long-term photostability into the CNFs hydrogel networks with soft, high specific surface area and good biocompatibility in a single step. The fluorescence of Mn:ZnS QDs@CNHs is quenched, which attributing to static quenching by Hg2+. The addition of GSH into the Mn:ZnS QDs@CNHs-Hg2+ system, which leads to the competitive affinity of Hg2+ to GSH and the functional groups on the surface of Mn:ZnS QDs@CNHs, resulting in fluorescence recovery. The proposed assay showed a detection limit of 57 nM within the linear range of 0.2–20 μM for detection of GSH. The biosensor is self-calibrating and enables in situ sensing without sample contamination, while allowing continuous detection of GSH in biological environments with good reversibility and good recovery.