FRET-Based Upconversion Nanoprobe Sensitized by Nd3+ for the Ratiometric Detection of Hydrogen Peroxide in Vivo

The exorbitant level of hydrogen peroxide is closely related to many human diseases. The development of novel probes for H2O2 detection will be beneficial to disease diagnosis. In this study, a novel Nd3+-sensitized upconversion nanoprobe based on Förster resonance energy transfer was first developed for sensing H2O2. This nanosystem was made of core–shell upconversion nanoparticles (emission at 540 and 660 nm), dicyanomethylene-4H-pyran (DCM)–H2O2, and poly acrylic acid (PAA)–octylamine. Obviously, upconversion nanoparticles (UCNPs) doped with Nd3+ acted as an energy donor, and DCM–H2O2, transferring to DCM–OH with the reaction of H2O2, acted as an energy acceptor. The ratiometric upconversion luminescence (540 nm/660 nm) signal could be utilized to visualize the H2O2 level, and the LOD of the nanoprobe for H2O2 was quantified to be 0.168 μM. Meanwhile, owing to the dope of Nd3+, the nanoprobe would not induce the overheating effect in biological samples and could possess deeper tissue penetration depth, compared with the UCNPs excited by 980 nm light during bioimaging. The nanoprobe could also play an important role in detecting the exogenous and endogenous H2O2 in living cells with ratiometric UCL (upconversion luminescence) imaging. Furthermore, our nanoprobe could function in detecting the H2O2 in a tumor-bearing mouse model. Therefore, this novel nanoprobe along with the ratiometric method for responding and bioimaging H2O2 could serve as a new model that promotes the emergence of novel probes for H2O2 detection.