A bimodal time-gated luminescence–magnetic resonance imaging nanoprobe based on a europium(iii) complex anchored on BSA-coated MnO2 nanosheets for highly selective detection of H2O2

Abstract

A novel nanocomposite, [Eu(BTD)₃(DPBT)]–BSA@MnO₂, is reported to serve as an effective nanoprobe for bimodal time-gated luminescence (TGL) and magnetic resonance (MR) imaging of H₂O₂ in vitro and in vivo. The nanoprobe was fabricated by immobilizing visible-light-excitable Eu³⁺ complexes in bovine serum albumin (BSA)-coated lamellar MnO₂ nanosheets. The TGL of the Eu³⁺ complex was effectively quenched by the MnO₂ nanosheets. Upon exposure to H₂O₂, the MnO₂ nanosheets underwent reduction to Mn²⁺, which simultaneously triggered rapid, selective and sensitive “turn-on” responses toward H₂O₂ in both TGL and MR detection modes. The presence of a protective “corona” formed by BSA enables the nanoprobe to withstand high concentrations of glutathione (GSH), a strong reducing agent of MnO₂ nanosheets. This capability allows the nanoprobe to be utilized for detecting H₂O₂ in living biosamples. The combined utilization of TGL and MR detection modes enables the nanoprobe to image H₂O₂ across a wide range of resolutions, from the subcellular level to the whole body, without any depth limitations. The results obtained from these modes can be cross-validated, enhancing the accuracy of the detection. The capability of the nanoprobe was validated by TGL imaging of endogenous and exogenous H₂O₂ in live HeLa cells, as well as bimodal TGL–MR imaging of H₂O₂ in tumor-bearing mice. The research achievements suggest that the integration of luminescent lanthanide complexes with protein-coated MnO₂ nanosheets offers a promising bimodal TGL–MR sensing platform for H₂O₂ in vitro and in vivo.