Sensitive and responsive upconversion nanoprobes for fluorescence turn-on detection of glucose concentration

Various approaches for detecting glucose concentration in real time are emerging at a breakneck pace. Glucose metabolism is closely linked to severe pathological events, which would either cause or predispose many progressive diseases in human. Herein, hydrophilic upconversion nanoprobes NaGdF₄: Yb³⁺, Er³⁺@Ag anchored with glucose oxidase (GOx) for glucose detection with lower detection limits have been efficaciously constructed. In the upconversion nanoprobes, NaGdF₄: Yb³⁺, Er³⁺ cores, and Ag layers act as energy donors and effective quenchers, respectively, through energy transfer. Moreover, the layer of Ag may disintegrate by H₂O₂ in the presence of glucose when glucose oxidase anchoring on the exterior of NaGdF₄: Yb³⁺, Er³⁺@Ag nanoprobes, which leads to the phenomenon of upconverting emission recovery. Additionally, NaGdF₄: Yb³⁺, Er³⁺@Ag-GOx has an ultralow detection limit of 1.77 μmol L⁻¹ on glucose detection, and it can achieve optical bioimaging to distinguish cancer cells from normal cells. As a result, the NaGdF₄: Yb³⁺, Er³⁺@Ag nanoprobes could be expanded to detect diverse H₂O₂-involved analytes. Overall, this nanoprobe has promising potential to be a compelling tool for the biomedical applications.