Ultrasmall MnSe Nanoparticles as T₁-MRI Contrast Agents for In Vivo Tumor Imaging

Magnetic resonance imaging (MRI) has excellent potential in the clinical monitoring of tumors because it can provide high-resolution soft tissue imaging. However, commercial contrast agents (CAs) used in MRI still have some problems such as potential toxicity to the human body, low relaxivity, and a short MRI acquisition window. In this study, ultrasmall MnSe nanoparticles are synthesized by living Staphylococcus aureus cells. The as-prepared MnSe nanoparticles are monodispersed with a uniform particle size (3.50 ± 0.52 nm). Due to the ultrasmall particle size and good water solubility, the MnSe nanoparticles exhibit in vitro high longitudinal relaxivity properties (14.12 ± 1.85 mM^-1·s^-1). The CCK-8 colorimetric assay, histological analysis, and body weight results show that the MnSe nanoparticles do not have appreciable toxicity on cells and organisms. Besides, the MnSe nanoparticles as T₁-MRI CAs offer a long MRI acquisition window to tumor imaging (∼7 h). This work provides a promising T₁-MRI CA for clinical tumor imaging and a good reference for the application of functional MnSe nanoparticles in the biomedicine field.