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

A Forster resonance energy transfer (FRET)-based biosensor using Cu nanoclusters (NCs) as energy donors and signal magnifiers and MnO2 nanospheres as both energy acceptors and target recognizers for selective detection of glutathione (GSH) was developed. MnO2 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 MnO2 nanospheres into Mn2+. 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 mu M, with a detection limit of 17 mu M. 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 nano-medicine and environmental science.