Gadolinium-chelate nanoparticle entrapped human mesenchymal stem cell via photochemical internalization for cancer diagnosis.

To improve the gadolinium (Gd) internalization efficiency in stem cells, gadolinium-chelate nanoparticles were prepared from a pullulan derivative (pullulan-deoxycholic acid (DOCA)-diethylene triamine pentaacetic (DTPA)-Gd conjugate; PDDG) and then the PDDG was entrapped into human mesenchymal stem cells (hMSCs) by the photochemical-internalization (PCI) method for cancer diagnosis via the cancer homing property of hMSCs. The internalization efficiency of Gd in hMSCs was significantly increased to 98 ± 4 pg Gd/cell from 32 ± 2 pg Gd/cell via the PCI method. Moreover, the Gd-entrapped hMSCs revealed a low exocytosis ratio of gadolinium-chelate nanoparticles during cell division in vitro and a high cellular labeling efficiency for at least 21 days in vivo. The cancer-targeting and diagnosis effect of the Gd-entrapped hMSCs were confirmed in a small CT26 tumor-bearing mice model. The stem cells detected an early tumor (∼3 mm(3)) within 2 h using 4.7-T MR and optical imaging. The results demonstrated that the PCI-mediated internalization of Gd-incorporated nanoparticles into hMSCs is a promising protocol for efficient cell labeling and tracking.