pH-responsive albumin-mimetic synthetic nanoprobes for magnetic resonance/fluorescence imaging of thyroid cancer

The combination of magnetic resonance and fluorescence imaging in dual-modality imaging not only resolves the limitations of conventional single molecular imaging techniques in terms of specificity, sensitivity, and resolution but also expands the possibilities of molecular imaging techniques in diagnostics and therapeutic monitoring. Herein, a novel pH-responsive magnetic resonance/near-infrared fluorescence (MR/NIRF) nanoprobe (MnO₂@BSA-Cy5.5) was successfully prepared by biomineralizing manganese dioxide (MnO₂) with bovine serum albumin (BSA) while coupling fluorescent dye Cy5.5 for precise tumor detection and visualization. The synthesized MnO₂@BSA-Cy5.5 nanoprobes were spherical particles of approximately 22.62 ± 3.31 nm in size, and their relaxation rates and T₁ imaging signals were activated-enhanced in an acidic environment. Cytotoxicity assay and hematoxylin and eosin staining demonstrated that MnO₂@BSA-Cy5.5 had low cytotoxicity and good biocompatibility. More importantly, active targeting via solid tumor albumin-binding protein receptor and enhanced permeability and retention effect, the probe can be specifically aggregated to the tumor site of the 8305C tumor model and exhibit excellent MR/NIRF imaging properties. Our results show that MnO₂@BSA-Cy5.5 has high resolution and sensitivity in tumor imaging and is expected to be applied as an MR/NIRF contrast agent for accurate diagnosis of thyroid cancer.