Transferrin Modified Gold Nanoclusters-Based Biosensing Nanoplatform for High-Precision Multimodal Bioimaging of Tumor Cells

Bioimaging technology has been broadly used in biomedicine, and the growth of multimodal imaging technology based on synergistic advantages can overcome the shortcomings of traditional single-modal bioimaging methods and attain high specificity and sensitivity in the fields of bioimaging and biosensing. The analysis of low-abundance microRNAs (miRNAs) in complex organisms is of high importance for early-stage diagnosis and clinical treatment of tumors. In our current study, a biosensing nanoplatform based on Tf-AuNCs and MnO₂ nanosheets was developed for multimodal imaging of tumor cells. First, oxidizable MnO₂ nanosheets provided a smart tool for use as nanocarriers and contrast agents for intracellular glutathione (GSH)-activated magnetic resonance imaging (MRI). Then, MnO₂ nanosheets delivered Tf-AuNC-based biosensing nanoplatforms into cells through endocytosis. Endogenous GSH degraded MnO₂ nanosheets into Mn²⁺, and the released functional nucleic acid probes can perform specific biosensing responses to miR-21 exhibiting multimodal imaging including two-photon near-infrared fluorescence imaging (TP-NIRFI), fluorescence lifetime imaging (FLIM), and MRI. Finally, the biosensing nanoplatform achieved satisfactory results in tumor cells and tissues by TP-NIRFI (300.0 μm penetration depth), FLIM (τ ≈ 50.0 ns), and MRI. Therefore, biosensing nanoplatforms based on Tf-AuNCs and MnO₂ nanosheets show great potential for multimodal detection and imaging in tumor cells.