Upconversion nanoparticles-CuMnO₂ nanoassemblies for NIR-excited imaging of reactive oxygen species in vivo

Here, we designed a ratiometric luminescent nanoprobe based on lanthanide-doped upconversion nanoparticles-CuMnO₂ nanoassemblies for rapid and sensitive detection of reactive oxygen species (ROS) levels in living cells and mouse. CuMnO₂ nanosheets exhibit a wide absorption range of 300-700 nm, overlapping with the visible-light emission of upconversion nanoparticles (UCNPs), resulting in a significant upconversion luminescence quenching. In an acidic environment, H₂O₂ can promote the redox reaction of CuMnO₂, leading to its dissociation from the surface of UCNPs and the restoration of upconversion luminescence. The variation in luminescence intensity ratio (UCL₄₇₅/UCL₄₅₀) were monitored to detect ROS levels. The H₂O₂ nanoprobe exhibited a linear response in the range of 0.314-10 μM with a detection limit of 11.3 nM. The biological tests proved the excellent biocompatibility and low toxicity of obtained UCNPs-CuMnO₂ nanoassemblies. This ratiometric luminescent nanoprobe was successfully applied for the detection of exogenous and endogenous ROS in live cells as well as in vivo ROS quantitation. The dual transition metal ions endow this probe efficient catalytic decomposition capabilities, and this sensing strategy broadens the application of UCNPs-based nanomaterials in the field of biological analysis and diagnosis.