Multifunctional manganese-doped core–shell quantum dots for magnetic resonance and fluorescence imaging of cancer cells

Abstract

We synthesized cadmium-free CuInS₂–Zn_1−xMn_xS core–shell quantum dots (QDs) for use in dual-mode optical and magnetic resonance (MR) imaging techniques. Manganese content was in the rang of 0.2–2.3% and varies with the amount of Mn²⁺ content in the reaction. These materials presented a high quantum yield (QY) of 52% in organic solvent. The CuInS₂–Zn_1−xMn_xS nanoparticles were subsequently transferred to the aqueous phase by the aid of cetyltrimethylammonium bromide (CTAB), and the QY values in water reached 18%. Relaxivity measurements showed that these materials had a T₁ relaxivity (r₁) of 7.2 mM⁻¹ s⁻¹ on the 3.0 T scanner, suggesting the possibility of using the nanoparticles as a T₁ contrast agent. The nanomaterials for both optical and MR imaging in aqueous solution were applied to cells in culture. These results showed that the QY and manganese concentration in the nanoparticles was sufficient to produce contrast for both modalities at relatively low concentrations of nanoparticles.