Settling dynamics of nanoparticles in simple and biological media

The biological response of organisms exposed to nanoparticles is often studied in vitro using adherent monolayers of cultured cells. In order to derive accurate concentration–response relationships, it is important to determine the local concentration of nanoparticles to which the cells are actually exposed rather than the nominal concentration of nanoparticles in the cell culture medium. In this study, the sedimentation–diffusion process of different sized and charged gold nanoparticles has been investigated in vitro by evaluating their settling dynamics and by developing a theoretical model to predict the concentration depth profile of nanoparticles in solution over time. Experiments were carried out in water and in cell culture media at a range of controlled temperatures. The optical phenomenon of caustics was exploited to track nanoparticles in real time in a conventional optical microscope without any requirement for fluorescent labelling that potentially affects the dynamics of the nanoparticles. The results obtained demonstrate that size, temperature and the stability of the nanoparticles play a pivotal role in regulating the settling dynamics of nanoparticles. For gold nanoparticles larger than 60 nm in diameter, the initial nominal concentration did not accurately represent the concentration of nanoparticles local to the cells. Finally, the theoretical model proposed accurately described the settling dynamics of the nanoparticles and thus represents a promising tool to support the design of in vitro experiments and the study of concentration–response relationships.

Development of an UPLC-MS/MS Method for Quantitative Analysis of Clotrimazole in Human Plasma Samples

An ultra-performance liquid chromatography-tandem mass spectrometry method was developed for the quantification of clotrimazole (CTZ) plasma levels after intravaginal administration of the drug given at approved dosages. Plasma samples were extracted by liquid–liquid extraction and a single chromatographic run could be completed within about 2 min. The method was linear over the investigated range (0.488–250 ng/mL) with all the correlation coefficients, R2, greater than 0.9903. All data were in the range of ±15.0% with respect to the nominal concentration for high QC and medium QC, and in the range ±20% with respect to the nominal concentration for low QC. This rapid and sensitive method was validated and could be applied to human plasma samples from a healthy volunteer, showing that the assay is able to detect plasma concentrations of CTZ in the range of those found after the administration of the drug at approved dosages in the clinical setting.

Sedimentation-Diffusion Behaviour of Nanoparticles

Background The biological response of organisms exposed to nanoparticles is often studied in vitro using adherent monolayers of cultured cells. In order to derive accurate concentration-response relationships, it is important to determine the local concentration of nanoparticles to which the cells are actually exposed rather than the nominal concentration of nanoparticles in the cell-culture medium. In this study, we investigated the sedimentation–diffusion process of different sized and charged gold nanoparticles in vitro by evaluating their settling dynamics and by developing a theoretical model to predict the concentration depth-profile of nanoparticles in solution over time.Results Experiments were carried out in water and in cell-culture media at a range of controlled temperatures. The optical phenomenon of caustics was exploited to track nanoparticles in real-time in a conventional optical microscope without any requirement for fluorescent labelling that potentially affects the dynamics of the nanoparticles. The results obtained demonstrate that size, temperature, and the stability of the nanoparticles play a pivotal role in regulating settling dynamics of nanoparticles. For gold nanoparticles larger than 60 nm in diameter, the initial nominal concentration did not accurately represent the concentration of nanoparticles local to the cells.Conclusion Nanoparticles dynamics in solution regulate the amount of material at the cellular level and must be taken into account when evaluating the biological response of organisms. the theoretical model proposed in this study accurately described the settling dynamics of the nanoparticles and thus represents a promising tool to support the design of in vitro experiments and the study of concentration-response relationships.

P64 Quality assessment for the continuous bioanalysis of aldosterone: application in an European paediatric study

BackgroundA validation is crucial to ensure the quality of an analytical method and its results. However, the validation is only a first step, further quality assessment has to be utilised to ensure high quality research. Specifications for the validation process, but also for the assessment of data, acquired in a study setting, are given by the EMA and FDA to ensure highest quality of the data.1 2MethodsA multi-level analytical quality system was established. Data of the calibration standards (CSs), quality control samples (QCs), and incurred sample reanalysis (ISR) were evaluated according to the specifications given by the EMA and FDA guidelines.[1,2] For a run to be considered valid ≥6 levels or 75% of the CSs and 67% of the QCs (≥50% per level) had to vary ≤±20% (LLOQ ≤±25%) from their nominal concentration.[1,2] For the ISR analysis at least 67% of the ISR samples have to lay in ±30% to the nominal concentration of the mean of the original and reanalysed value.[1]ResultsSeventy analytical runs were conducted, applying the quality measures, 79% runs were classified as valid and were used to determine unknown samples in a paediatric study. The high quality of the acquired data is reflected in the high conformity of the CSs and QCs to the EMA and FDA guidelines, 99% of the CSs and 95% of the QCs were accepted. Further underlining the high quality of the acquired data, 85% of the IRS have also been accepted. The assay was successfully used over a time period of 29 months.ConclusionThe results of the quality assessment confirmed the robustness of the aldosterone assay throughout the whole study duration. Thus, the samples measured by this assay are reliable and facilitate the high quality research in the paediatric population.ReferencesGuideline on bioanalytical method validation. European Medicines Agency, London, UK (2011).Guidance for Industry: Bioanalytical Method Validation. US Department of Health and Human Services, US FDA Rockville, MD, USA (2018).Disclosure(s)Nina Makowski, Ilja Burdman, Mohsin Ali, Bartel A, Bjoern B. Burckhardt declare that there is no conflict of interest. The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007–2013) under grant agreement n°602295 (LENA).

Reproductive effects of endocrine disrupting chemicals, bisphenol-A and 17β-oestradiol, on Cerastoderma edule from south-west England: field study and laboratory exposure

Endocrine disruption has rarely been reported in field populations of the edible cockle and the context with the general health of the shellfish is unclear. This study examined the reproductive state of two Cerastoderma edule populations over a 6-month period to assess their reproductive condition, the incidence of intersex and presence of parasitic infection. A further seven native sites from south-west England were examined during the peak reproductive season to identify the presence of intersex within the region. Laboratory exposures of organisms collected from field populations showed a significantly female-biased sex ratio compared with controls when exposed to the endocrine disrupting chemicals, bisphenol-A (nominal concentration: 0.1 µg L−1) and 17β-oestradiol (nominal concentration: 0.1 µg L−1), but none of the chemical exposures induced intersex. Intersex was revealed in seven out of the nine native populations of C. edule sampled at peak reproductive season. The highest incidence and most severe case of intersex were reported at Lower Anderton on the River Tamer which also had a significantly female-biased sex ratio. Additionally, the dominant trematode family was the Bucephalaidae. Parasitic infection influences the maturity of C. edule by lowering both mean gonad index and condition index. These results suggest that endocrine disrupting chemicals could be contributing factors towards the development of intersex in C. edule.

Crystal Growth and Scintillation Properties of Ce3+ and Mg2+ Co-Doped LiCaAlF6 Single Crystal

Ce and Mg Co-Doped LiCaAlF6 (LiCAF) Single Crystals Were Grown by Micro-Pulling-down (μ-PD) Method and the Optical and Scintillation Properties of Obtained Crystals Were Measured. The Grown Crystals Were Crack-Free and Had 30-50 mm in Length and 2 Mm in Diameter. Absorption Coefficients Were Proportional to the Ce Nominal Concentrations. the Radioluminescence Spectra under 5.5 Mev Alpha-Ray Irradiation Showed Emission Peak at 290 and 310 nm due to Ce3+ 5d-4f Transitions, and Were Agreement with those of Ce Single-Doped LiCaF. The Highest Light Yield under 5.5 Mev Alpha-Ray Irradiation of Ce 4% and Mg 2% Co-Doped LiCaF Was Found to Be 0.6 Times than that of Lithium Glass Scintillator GS-20. Comparing the Light Yield of Licaf Samples with the Fixed Ce Nominal Concentration and Different Mg Co-Doped Concentrations, the Light Yield Increased with an Increase of Mg Nominal Concentration. the Alpha-Ray Excited Decay Times Were Constantly 45-50 ns.

PrBa2Cu3O7-y: SUPERCONDUCTING OR ANOMALOUSLY MAGNETIC?

In PrBa 2 Cu 3 O 7-y (Pr123) single crystals grown by the flux method the kink in the magnetic susceptibility χab(T), connected with antiferromagnetic ordering of Pr, disappears after field cooling (FC) in a field H‖ab-plane whereas the kink in χc(T) remains unchanged after FC in H‖c-axis. This seems to be connected with the coupling between the Pr and Cu(2) sublattices. The Curie constant C determined from the data reported for superconducting Pr123 crystals grown by the traveling-solvent floating zone (TSFZ), method (Zou et al, Phys. Rev. Lett., 80, 1074 (1998)) is about one half of that for our flux-grown non-superconducting crystals. Thus, we propose that concentration of Pr in TSFZ crystals seems to be about one half of the nominal concentration for Pr123. Therefore, we propose that superconductivity in TSFZ samples is connected most probably with the partial substitution of Pr by nonmagnetic Ba.

Stability of topotecan infusion solutions in polyvinylchloride bags and elastomeric portable infusion devices

Purpose. The purpose of this study was to determine the physicochemical stability of topotecan after reconstitution and after further dilution in two commonly used infusion fluids (0.9% sodium chloride, 5% dextrose) in both polyvinylchloride (PVC) bags and elastomeric portable infusion devices. Methods. Each vial of topotecan (Hycamtin®) was reconstituted with sterile water for injection, yielding a nominal concentration of 1 mg/mL. Topotecan infusion solutions were aseptically prepared by further dilution of reconstituted topotecan solutions with either 0.9% sodium chloride or 5% dextrose in both PVC bags and portable elastomeric infusion devices, in amounts yielding topotecan concentrations of 10 µg/mL, 25 µg/mL, or 50 µg/mL. Test solutions were stored light-protected at room temperature (25°C) or under refrigeration (2-8°C) in parallel. One test solution of the nominal concentration of 10 µg/mL topotecan in a 0.9% sodium chloride PVC infusion bag was stored under ambient light conditions (mixed daylight and normal laboratory fluorescent light) at room temperature. Topotecan concentrations were obtained periodically throughout a 4-week storage period via a stability-indicating high performance liquid chromatography assay with ultra-violet detection. In addition, measurements of pH values were performed regularly, and test solutions were visually examined for colour change and precipitation. Results. The stability tests revealed that the currently available topotecan formulation is stable (at a level of ≥90% topotecan) after reconstitution and dilution, independent of temperature (refrigerated, room temperature), the vehicle (0.9% sodium chlo-ride, 5% dextrose), the concentration (10 µg/mL, 25 µg/mL, or 50 µg/mL), or the container material (PVC bags, elastomeric portable infusion devices). The results were obtained over a test period of ≥4 weeks. Topotecan infusion solutions exposed to daylight were stable for only 17 days. Conclusions. Reconstituted and diluted topotecan infusion solutions are shown to be physicochemically stable for 4 weeks. Light protection during administration is not necessary.