Ultrabright NIR fluorescent mesoporous silica nanoparticles.

Near-infrared (NIR) water-dispersible fluorescent tags are of big importance for biomedical imaging. Bright, stable, biocompatible NIR fluorescent nanoparticles have great translation potential to improve diagnosis of early stages of different diseases. Here we report on the synthesis of exceptionally bright ("ultrabright") fluorescent meso(nano)porous silica nanoparticles of 28 ± 3 nm in diameter. The NIR fluorescent dye LS277 is encapsulated inside these silica nanoparticles. The wavelengths of the maximum excitation/fluorescence of the particles are 804/815 nm. The absorptivity coefficient of the particles is 2.1 × 108 M-1 cm-1 at 805 nm and the quantum yield of the dye increased by a factor of 5 after encapsulating to 1.5%. The fluorescent brightness of these particles is more than 2000× higher than the fluorescence of one molecule of LS277 in water. When exited in NIR spectral region (>700 nm), these particles are up to 4× brighter than QD800 commercial quantum dots emitting at 800 nm. We demonstrate that the synthesized NIR mesoporous silica nanoparticles easily internalize 4T1luc breast tumor cells, and remain bright for more than 9 weeks whereas the dye is completely bleached by that time.

Preclinical evaluation of Mab CC188 for ovarian cancer imaging.

Cancer stem cells (CSCs) have been successfully isolated from solid tumors and are believed to be initiating cells of primary, metastatic and recurrent tumors. Imaging and therapeutic reagents targeted to CSCs have potential to detect subclinical tumors and completely eradicate the disease. Previously, we have demonstrated that Mab CC188 binds to colon cancer CD133- and CD133+ (CSCs) cells. In this study, we examined the reactivity of Mab CC188 to ovarian cancer cells including CD133+ cells and primary tumor tissues using immunofluorescence staining methods and tissue microarray technique. We also explored the feasibility of using NIR dye-labeled Mab CC188 probe to image ovarian tumors in vivo. Mab CC188 stains both CD133- and CD133+ cells of ovarian cancer. Tissue microarray analysis reveals that 75% (92/123) of ovarian cancer cases are positively stained with Mab CC188. Weak positive (±), positive (+), strong positive (++) and very strong positive (+++) stains are 14.8, 3.7, 11 and 24.4%, respectively. In contrast, Mab CC188 staining is low in normal cells and tissues. In vivo study show that significant amounts of the probe accumulates in the excretion organs in the early period postinjection. At 24 hr, the imaging probes have largely accumulates in the tumor, while the intensity of the imaging probe decreases in the liver. The tumor uptake was still evident at 120-hr postinjection. Our work suggests that Mab CC188-based imaging and therapeutic reagents are capable of detecting early stage ovarian tumors and effectively treating the tumor.

Postendocytic trafficking of epidermal growth factor-receptor complexes is mediated through saturable and specific endosomal interactions.

Intracellular trafficking of the epidermal growth factor receptor (EGF-R) is regulated by receptor occupancy. To investigate this, we developed an assay to study endosomal sorting under steady-state conditions. Using a cell line transfected with EGF-R variants, we found that the fraction of internalized EGF.EGF-R complexes sorted to lysosomes was a function of the number of intracellular complexes and required sequences in the cytoplasmic domain of the receptor. As the number of intracellular occupied wild-type receptors increased from 3 x 10(2) to 2 x 10(5)/cell, the fraction of internalized EGF that was degraded dropped from 70 to 20%. Transforming growth factor-alpha, which dissociates from the EGF-R at endosomal pH, was degraded to a uniform extent of approximately 50% at all intracellular ligand concentrations. EGF internalized by receptors lacking a cytoplasmic domain (c'647) was degraded to an extent of only 5-10% independent of the number of intracellular complexes. Mutant receptors truncated either at residues 1022 or 973 displayed sorting patterns intermediate between wild-type and c'647 receptors. Despite large differences in their internalization rates, the fractional sorting patterns of c'1022 and c'973 receptors were indistinguishable. Receptor tyrosine kinase activity appeared to have a small effect on sorting pattern, but only in the context of full-length receptors. Our results indicate that the default pathway of internalized receptors is rapidly recycling and that lysosomal targeting of occupied EGF-R is due to endosomal retention that is both specific and saturable. In addition, internalization and endosomal retention of EGF-R appear to be mediated by distinct structural elements.

The effects of allopurinol and clofibrate on the elimination of coumarin anticoagulants in man.

The effects of chronic treatment with allopurinol and clofibrate on the elimination from plasma of warfarin and dicoumarol were examined in man. In addition, the binding of warfarin to human serum proteins was measured with and without clofibrate and its metabolite chlorophenoxyisobutyric acid (CPIB), both present in therapeutic concentrations. Treatment with allopurinol and clofibrate did not alter the rate of elimination of warfarin from plasma. In addition, clofibrate and CPIB caused no significant displacement of warfarin from serum proteins. This evidence supports the conclusion that the clinically significant potentiation of warfarin activity by clofibrate in man is due to an interaction at the receptor site. In contrast, treatment with allopurinol resulted in significant prolongation of the plasma half-life of dicoumarol in one of three subjects. These data are consistent with inhibition of the metabolism of dicoumarol by allopurinol in some individuals.