Metastasis to regional lymph nodes is a significant prognostic indicator for cancer progression. There is a great demand for rapid and accurate diagnosis of metastasis to the lymph nodes. In this work, folate receptor‐targeted trimodal polymer dots are designed for near‐infrared (NIR)/photoacoustic (PA)/magnetic resonance (MR) imaging of lymph node metastasis. Confocal microscopic analyses and flow cytometry show that pulmonary mucosa epithelial cell carcinoma NCI‐H292 with expression of the folate receptor is positive for folate‐functional polymer dots. In vivo and ex vivo NIR imaging results verify that prepared polymer dots show rapid and high uptake in the metastatic lymph nodes, can effectively distinguish metastatic and normal lymph nodes for 1 h postinjection, and have great potential in real‐time imaging‐guided surgery. Furthermore, ten metastatic lymph nodes from the tumor‐bearing mice are detected by NIR imaging via intratumoral injection of polymer dots. Moreover, in vivo PA and MR imaging confirm the enhanced PA and MR signals of polymer dots in the metastatic lymph nodes as well as enlarged lymph nodes in tumor‐bearing mice. The results of this study provide a unique approach using trimodal polymer dots for the rapid and precise diagnosis of lymph node metastasis in vivo.

Near-infrared-emitting polymer dots were prepared and used as fluorescent nanoprobes for in vitro HeLa cell labeling and in vivo long-term HeLa tumor tracking. The prepared NIR polymer dots showed no obvious effect on the tumor growth, and exhibited durable brightness, long-term photostability and high sensitivity.

Ultrasmall sub-5 nm KGdF4 rare earth nanoparticles were synthesized as multifunctional probes for fluorescent, magnetic, and radionuclide imaging. The cytotoxicity of these nanoparticles in human glioblastoma U87MG and human non-small cell lung carcinoma H1299 cells was evaluated, and their application for in vitro and in vivo tumor targeted imaging has also been demonstrated.

Folic acid functionalized PFBT-COOH and PFBT-NH 2 polymer dots were prepared using a nano precipitation method, and their applications for tumor imaging in vitro and in vivo were demonstrated for the first time. The synthesized FA-PFBT-COOH polymer dots were 50-60 nm in diameter with a zeta potential of greater than 30 mV in water, while the synthesized FA-PFBT-NH 2 polymer dots were 90-105 nm in diameter with a zeta potential of greater than 20 mV in water. Furthermore, the FA-PFBT-COOH polymer dots produced stronger fluorescence intensity in water solution as well as in the cells than the FA-PFBT-NH 2 polymer dots, and were able to image H1299 tumors in living mice after intravenous injection. This study showed the great potentials of FA-PFBT-COOH polymer dots as fluorescent nanoprobes for biomedical imaging.

Fluorescent nanoprobes have become one of the most promising classes of materials for cancer imaging. However, there remain many unresolved issues with respect to the understanding of their long-term colloidal stability and photostability in both biological systems and the environment. In this study, we report long-term-stable near-infrared (NIR) polymer dots for in vivo tumor vasculature imaging. NIR-emitting polymer dots were prepared by encapsulating an NIR dye, silicon 2,3-naphthalocyanine bis(trihexylsilyloxide) (NIR775), into a matrix of polymer dots, poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), using a nanoscale precipitation method. The prepared NIR polymer dots were sub-5 nm in diameter, exhibited narrow-band NIR emission at 778 nm with a full width at half-maximum of 20 nm, and displayed a large Stokes shift (>300 nm) between the excitation and emission maxima. In addition, no significant uptake of the prepared NIR polymer dots by either human glioblastoma U87MG cells or human non-small cell lung carcinoma H1299 cells was detected. Moreover, these NIR polymer dots showed long-term colloidal stability and photostability in water at 4 °C for at least 9 months, and were able to image vasculature of xenografted U87MG tumors in living mice after intravenous injection. These results thus open new opportunities for the development of whole-body imaging of mice based on NIR polymer dots as fluorescent nanoprobes.