An inorganic magnetic fluorescent nanoprobe with favorable biocompatibility for dual-modality bioimaging and drug delivery.

In this work, we present the development of a high water soluble biological nanoprobe through the covalent bonding of β-CD onto the surface of iron oxide‑gold nanoclusters (Fe3O4@Au@β-CD). Fe3O4@Au@SiO2 NPs were also prepared for comparison. The maximum emission peak of magnetic fluorescent NPs red-shifted by 30 nm and the lifetime was also elongated to 5.21 μs after surface modified with β-CD. The relaxivities and in vitro magnetic resonance imaging ability of the resultant magnetic fluorescent NPs were also studied, indicating that Fe3O4@Au@β-CD NPs have the lowest r2/r1 ratio and could be a potential T2 contrast agent for MR imaging. The MTT assay proved that, Fe3O4@Au@β-CD NPs are of excellent water solubility and biocompatibility. In vitro confocal fluorescence imaging was also performed, manifesting that Fe3O4@Au@β-CD NPs can be selectively uptaken by gastric cancer cells (MGC-803) and exhibit red fluorescence in the cells. The preliminary drug loading and releasing measurements demonstrate that it can also act as targeted drug delivery nanosystem. All these experimental results indicate that, Fe3O4@Au@β-CD NPs hold great application perspective in the diagnosis and therapy of gastric cancer cells as biological nanoprobes.