Polyol-Made Luminescent and Superparamagnetic ß-NaY0.8Eu0.2F4@γ-Fe2O3 Core-Satellites Nanoparticles for Dual Magnetic Resonance and Optical Imaging.

Red luminescent and superparamagnetic ß-NaY0.8Eu0.2F4@γ-Fe2O3 nanoparticles, made of a 70 nm-sized ß-NaY0.8Eu0.2F4 single crystal core decorated by a 10 nm-thick polycrystalline and discontinuous γ-Fe2O3 shell, have been synthesized by the polyol process. Functionalized with citrate ligands they show a good colloidal stability in water making them valuable for dual magnetic resonance and optical imaging or image-guided therapy. They exhibit a relatively high transverse relaxivity r2 = 42.3 mM-1·s-1 in water at 37 °C, for an applied static magnetic field of 1.41 T, close to the field of 1.5 T applied in clinics, as they exhibit a red emission by two-photon excited fluorescence microscopy. Finally, when brought into contact with healthy human foreskin fibroblast cells (BJH), for doses as high as 50 µg·mL-1 and incubation time as long as 72 h, they do not show evidence of any accurate cytotoxicity, highlighting their biomedical applicative potential.

Uptake and excretion dynamics of gold nanoparticles in cancer cells and fibroblasts.

Radiotherapy is one of the main treatments used to fight cancer. A major limitation of this modality is the lack of selectivity between cancerous and healthy tissues. One of the most promising strategies proposed in this last decade is the addition of nanoparticles with high-atomic number to enhance radiation effects in tumors. Gold nanoparticles (AuNPs) are considered as one of the best candidates because of their high radioenhancing property, simple synthesis and low toxicity. Ultra small AuNPs (core size of 2.4 nm and hydrodynamic diameter of 4.5 nm) covered with dithiolated diethylenetriaminepentaacetic acid (Au@DTDTPA) are of high interest because of their properties to bind MRI active or PET active compounds at their surface, to concentrate in some tumors and be eliminated via renal clearance thanks to their small size. These key figures make Au@DTDTPA the best candidate to develop image-guided radiotherapy. Surprisingly the capacity of the nanoparticles to penetrate cells, an important issue to predict radioenhancement, has not been established yet. Here, we report the uptake dynamics, internalization routes and excretion dynamics of Au@DTDTPA nanoparticles in various cancer cell lines including glioblastoma (U87-MG), chordoma (UM-Chor1), cervix (HeLa), prostate (PC3), and pancreatic (BxPC-3) cell lines as well as fibroblasts (Dermal fibroblasts). This study demonstrates a strong cell line dependence of the nanoparticle uptake and excretion dynamics. Different pathways of cell internalization evidenced here explain this dependence. As a major finding, the retention of Au@DTDTPA nanoparticles was found to be higher in cancer cells than in fibroblasts. This result strengthens the strategy of using nanoagents to improve tumor selectivity of radiation treatments. In particular Au@DTDTPA nanoparticles are good candidates to improve the treatment of radioresitant gliobastoma, pancreatic and prostate cancer in particular. In conclusion, the variability of cell-to-nanoparticle interaction is a new parameter to consider in the choice of nanoagents in a combined treatment.

Characterization, comparison, and choice of a commercial double-clad fiber for nonlinear endomicroscopy.

Several endomicroscope prototypes for nonlinear optical imaging were developed in the last decade for in situ analysis of tissue with cellular resolution by using short infrared light pulses. Fourier-transform-limited pulses at the tissue site are necessary for optimal excitation of faint endogenous signals. However, obtaining these transform-limited short pulses remains a challenge, and previously proposed devices did not achieve an optimal pulse delivery. We present a study of fibered endomicroscope architecture with an efficient femtosecond pulse delivery and a high excitation level at the output of commercially available double-clad fibers (DCFs). The endomicroscope incorporates a module based on a grism line to compensate for linear and nonlinear effects inside the system. Simulations and experimental results are presented and compared to the literature. Experimentally, we obtained short pulses down to 24 fs at the fiber output, what represents to the best of our knowledge the shortest pulse duration ever obtained at the output of a nonlinear endoscopic system without postcompression. The choice of the optimal DCF among four possible commercial components is discussed and evaluated in regard to multiphoton excitation and fluorescence emission.