Transferrin\nModified Gold Nanoclusters-Based Biosensing\nNanoplatform for High-Precision Multimodal Bioimaging of Tumor Cells

Bioimaging technology has been broadly used in biomedicine,\nand\nthe growth of multimodal imaging technology based on synergistic advantages\ncan overcome the shortcomings of traditional single-modal bioimaging\nmethods and attain high specificity and sensitivity in the fields\nof bioimaging and biosensing. The analysis of low-abundance microRNAs\n(miRNAs) in complex organisms is of high importance for early-stage\ndiagnosis and clinical treatment of tumors. In our current study,\na biosensing nanoplatform based on Tf-AuNCs and MnO<sub>2</sub> nanosheets\nwas developed for multimodal imaging of tumor cells. First, oxidizable\nMnO<sub>2</sub> nanosheets provided a smart tool for use as nanocarriers\nand contrast agents for intracellular glutathione (GSH)-activated\nmagnetic resonance imaging (MRI). Then, MnO<sub>2</sub> nanosheets\ndelivered Tf-AuNC-based biosensing nanoplatforms into cells through\nendocytosis. Endogenous GSH degraded MnO<sub>2</sub> nanosheets into\nMn<sup>2+</sup>, and the released functional nucleic acid probes can\nperform specific biosensing responses to miR-21 exhibiting multimodal\nimaging including two-photon near-infrared fluorescence imaging (TP-NIRFI),\nfluorescence lifetime imaging (FLIM), and MRI. Finally, the biosensing\nnanoplatform achieved satisfactory results in tumor cells and tissues\nby TP-NIRFI (300.0 μm penetration depth), FLIM (τ ≈\n50.0 ns), and MRI. Therefore, biosensing nanoplatforms based on Tf-AuNCs\nand MnO<sub>2</sub> nanosheets show great potential for multimodal\ndetection and imaging in tumor cells.