Silica Nanoparticles Decorated with Gadolinium Oxide\nNanoparticles for Magnetic Resonance and Optical Imaging of Tumors

Abstract

We\nreport a type of core@dotted-shell structured nanoprobe that\nincorporates water-soluble silica and water-interacted gadolinium\noxide, endowed with excellent hydrophilicity and high magnetic resonance\nimaging (MRI) relaxivity. The nanoprobes are monodispersed and uniformed\nwith a superior stability due to the formation of Gd–O–Si\nbonds. The nanoprobe possesses an MRI relaxivity of 39.08 mM^–1 s^–1, 9.3 times that of clinical Gd chelates, gaining\na significant MRI enhancement <i>in vivo</i>; the classical\nSolomon–Bloembergen–Morgan theory is applied to explicate\nthe relaxation enhancement mechanism. Multicolor and enhanced emissions\nare tunable through adjusting Yb³⁺/Li⁺-doping\nconcentrations in Gd₂O₃:Yb³⁺/Er³⁺/Li⁺. A theoretical model based on the rate equations\nof upconversion energy-transfer processes is established to address\nthe nanoprobe’s photoluminescence. Cross-linked with folate-PEG,\nthe nanoprobe can be absorbed by nasopharyngeal, cervical, and breast\ncarcinoma cells, rendering a vivid multicolor living cell imaging.\nThe nanoprobe owns a negligible nanotoxicity according to <i>in vitro</i> cytotoxicity and <i>in vivo</i> immunotoxicity,\nhistopathology, and hematology assays. This study demonstrates that\nfolate-PEGylated SiO₂@Gd₂O₃:5%Yb³⁺/2%Er³⁺/6%Li⁺ core@dotted-shell nanoprobes\ndesignated for multimodal imaging can achieve simultaneously enhanced\nMR relaxivity, photoluminescence efficiency, tumor-targeting ability,\nand biocompatibility. Both designing of nanoprobe and addressing MR/photoluminescence\nenhancement mechanism facilitate the development of practical multimodal\nimaging nanoprobes for accurate diagnosis of early tumors.