The development of multimodal nanoprobes that combined properties of near-infrared (NIR) fluorescence and magnetic resonance imaging (MRI) within a single probe is very important for medical diagnosis. The NIR-emitting persistent luminescent nanoparticles (PLNPs) are ideal for optical imaging owing to no need for in situ excitation, the absence of background noise, and deep tissue penetration. However, no PLNP based multimodal nanoprobes have been reported so far. Here, we report a novel multimodal nanoprobe based on the gadolinium complexes functionalized PLNPs (Gd(III)-PLNPs) for in vivo MRI and NIR luminescence imaging. The Gd(III)-PLNPs not only exhibit a relatively higher longitudinal relaxivity over the commercial Gd(III)-diethylenetriamine pentaacetic acid complexes but also keep the superlong persistent luminescence. The prepared Gd(III)-PLNPs multimodal nanoprobe offers great potential for MRI/optical imaging in vivo.

Facile fabrication of multimodal imaging probes is highly desired for bioimaging application due to their integrated advantages of several imaging modalities. Here, we report a simple and one-step mild strategy to fabricate a multifunctional Gd2O3/Au hybrid nanoprobe. Bovine serum albumin (BSA) was used as the template in the biomineralization synthesis. The fabricated BSA-Gd2O3/Au nanoprobe showed excellent chemical stability, intense near-infrared (NIR) fluorescence, and good magnetic resonance imaging (MRI) ability. The multimodal imaging potential of the prepared multifunctional nanoprobe was demonstrated by successful NIR fluorescent and magnetic resonance blood pool imaging. Further modification of BSA-Gd2O3/Au with arginine-glycine-aspartic acid peptide c(RGDyK) (RGD) enabled the nanoprobe for targeted tumor imaging in vivo.

Rational design and fabrication of multimodal imaging nanoprobes are of great significance for in vivo imaging. Here we report the fabrication of a multishell structured NaYF4:Yb/Tm@NaLuF4@NaYF4@NaGdF4 nanoprobe via a seed-mediated epitaxial growth strategy for upconversion luminescence (UCL), X-ray computed tomography (CT), and magnetic resonance (MR) trimodal imaging. Hexagonal phase NaYF4:Yb/Tm is used as the core to provide UCL, while the shell of NaLuF4 is epitaxially grown on the core not only to provide an optically inert layer for enhancing the UCL but also to serve as a contrast agent for CT. The outermost NaGdF4 shell is fabricated as a thin layer to give the high longitudinal relaxivity (r1) desired for MR imaging. The transition shell layer of NaYF4 not only provides an interface to facilitate the formation of NaGdF4 shell but also inhibits the energy transfer from inner upconversion activator to surface paramagnetic Gd(3+) ions. The fabricated multishell structured nanoprobe shows intense near-infrared UCL, high r1 value of 3.76 mM(-1) s(-1), and in vitro CT contrast effect. The multishell structured nanoprobe offers great potential for in vivo UCL/CT/MR trimodal imaging. Further covalent bonding of folic acid makes the multishell structured nanoprobe promising for in vivo targeted UCL imaging of tumor-bearing mice.

Metastasis is the primary cause of cancer morbidity and mortality. To obtain an effective diagnosis and treatment, precise imaging of tumor metastasis is required. Here we prepared persistent luminescent nanoparticles (PLNPs) containing a hydrogel (PL-gel) for targeted, sustained, and autofluorescence-free tumor metastasis imaging. PLNPs offered renewable long-lasting near-infrared (NIR) emitting without in situ radiation, favoring deep tissue penetration imaging without background interference. PLNPs were conjugated with 4-carboxyphenyl boronic acid (CPBA) to yield PLNPs-CPBA, which specifically recognized metastatic breast cancer cells (MBA-MD-231 cells) and enabled receptor-mediated endocytosis for specific cancer cell labeling. The PLNPs-CPBA-labeled cancer cells enabled sensitive imaging performance and high viability without influencing the migration and invasiveness of cancer cells for long-term tracking. PLNPs-CPBA were further encapsulated inside alginate to generate PL-gel for sustained PLNPs-CPBA release and tumor cell labeling, and the PL-gel showed enhanced renewable persistent luminescence compared to the PLNPs-CPBA suspension. The metastasis in the mouse breast cancer model was continuously tracked by persistent luminescence imaging, showing that PL-gel achieved noninvasive and highly selective imaging of tumor metastasis without background interference. Our PL-gel could be rationally designed to specifically target other types of cancer cells and thus provide a powerful and generic platform for the study of tumor metastasis.