A FRET biosensor based on MnO2 nanosphere/copper nanocluster complex: From photoluminescence quenching to recovery and magnification

A Förster resonance energy transfer (FRET)-based biosensor using Cu nanoclusters (NCs) as energy donors and signal magnifiers and MnO 2 nanospheres as both energy acceptors and target recognizers for selective detection of glutathione (GSH) was developed. MnO 2 nanospheres, synthesized through an ultrasonication assisted top down method, can quench the photoluminescence (PL) of Cu NCs through FRET, after forming complex through electrostatic interactions. GSH can recover PL of Cu NCs by triggering the decomposition of complex through digesting MnO 2 nanospheres into Mn 2+ . Additionally, the PL can be further magnified through the host-guest interactions between GSH and Cu NCs, with around 25 times higher than the original intensity and 3 times higher than the initial PL intensity of Cu NCs. Under the optimum conditions, the FRET based sensor can detect GSH in the concentration range from 0 to 140 μM, with a detection limit of 17 μM. Moreover, the proposed method shows a strong anti-interference ability, achieving the sensitive directly detection of GSH in human whole blood samples. Our results provide insights in designing FRET based sensors. Moreover, all the components are nontoxic and biodegradable, demonstrating their potential applications in other fields such as nanomedicine and environmental science.