Counting Single Rhodamine 6G Dye Molecules in Organosilicate Nanoparticles

Rhodamine 6G (R6G) dye molecules have been embedded into organosilicate nanoparticles to improve thermal and chemical stability of these marker molecules. We demonstrate that the well-established method of optical single-particle microscopy can be used to determine the number of dye molecules per nanoparticle in such hybrid materials. Analysing the fluorescence intensity of R6G in single nanoparticles, we obtain an average number of 1.3 - 1.7 dye molecules per nanoparticle as compared to 1 R6G per particle obtained from ensemble experiments. The blinking behaviour of embedded R6G can be described by a power law with an exponent α(on/off) = - 1.7. Ensemble measurements complete the optical characterization of the nanoparticles, which reveals no pronounced R6G aggregate formation.

Detection and stability of nanoscale space charges in local oxidation nanolithography

We report on the stability of space charges within nanoscale silicon oxide patterns generated by atomic force microscope tip-induced local anodic oxidation of alkyl-terminated silicon. Surface potentials of these structures are investigated using two different approaches: Kelvin probe force microscopy and the spectroscopy of adsorbed charge-sensitive dye molecules. Both techniques prove that there is no decay of the space charge itself at least for several days. The apparent decrease of the surface potential measured with the Kelvin probe method is known to be influenced by the ambient humidity. It is supposed to be caused by a screening effect through the formation of a water layer. This is confirmed by our investigation of the surface potential decrease kinetics, which could be well fitted with an adapted model of water condensation. The fluorescence of the charge-sensitive dye di-4-ANEPPS, which is applied to the structures, shows a spectral shift of about 270 meV compared to an uncharged silicon oxide surface. The high stability of the charges supports the use of local anodic oxidation patterns as templates for selective immobilization of cationic species.

Adding the specific COX-2 inhibitor celecoxib to docetaxel plus carboplatin in first line for stage IC-IV epithelial ovarian cancer: A randomized phase II study

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Background: Inhibition of COX-2 reduces the growth rate of tumors in vitro and COX-2 is over-expressed in ovarian cancer, so a COX-2 inhibitor might be beneficial. Methods: After debulking surgery patients (pts) with advanced epithelial ovarian cancer (FIGO IC-IV) received docetaxel 75 mg/m2 and carboplatin AUC=5 (CT) for 6–9 cycles q 3-wks and were randomized to celecoxib 400 mg BID (COX) for max three years or to control (CTR), stratified for residual tumor present in 58% vs 54%. Response rates and progression-free survival were based on CA-125 levels according to Rustin. Primary endpoints were biochemical CR (bCR)and safety, secondary progression free- (PFS) and overall survival (OS). Results: 183 of 201 pts enrolled were analyzed and baseline characteristics were well balanced between COX (n = 91) and control (CTR) arms (n = 93). Safety: Docetaxel and carboplatin was given full dose in 89% vs 84% pts and creatinine clearance remained stable vs baseline in both arms (96% vs 97% at Cycle 6). Toxicity grade 3–4 (COX vs CTR) was neutropenia in 26 vs 32, febrile neutropenia 12 vs 12, N/V 6 vs 5, allergy 7 vs 0 pts. Neurosensory grade 2–3 was less in COX (4 vs 13 pts, p< 0.05). Efficacy: Median duration of COX treatment was 6 months and 60% completed the combination with six or more cycles of CT. At a median follow-up of 20 months, CA-125 normalized (bCR) in COX 55/74 (74%) and CTR 49/74 (66%) pts with elevated baseline levels (n.s.). Median PFS was 17.4 vs 14.5 months (n.s.) and median survival 34.2 vs 34.7 months (n.s.). Conclusions: Celecoxib added to docetaxel/carboplatin in epithelial ovarian cancer had no effect on creatinine clearance, CA-125 response, PFS or OS. Celecoxib during CT was associated with allergic skin reactions but less neurotoxicity.

No significant financial relationships to disclose.