Stacked optical antennas for plasmon propagation in a 5 nm-confined cavity

The sub-wavelength concentration and propagation of electromagnetic energy are two complementary aspects of plasmonics that are not necessarily co-present in a single nanosystem. Here we exploit the strong nanofocusing properties of stacked optical antennas in order to highly concentrate the electromagnetic energy into a 5 nm metal-insulator-metal (MIM) cavity and convert free radiation into guided modes. The proposed nano-architecture combines the concentration properties of optical nanoantennas with the propagation capability of MIM systems, paving the way to highly miniaturized on-chip plasmonic waveguiding

Acceptance criteria for new approach methods in toxicology and human health-relevant life science research - part I

Every test procedure, scientific and non-scientific, has inherent uncertainties, even when performed according to a standard operating procedure (SOP). In addition, it is prone to errors, defects, and mistakes introduced by operators, laboratory equipment, or materials used. Adherence to an SOP and comprehensive validation of the test method cannot guarantee that each test run produces data within the acceptable range of variability and with the precision and accuracy determined during the method validation. We illustrate here (part I) why controlling the validity of each test run is an important element of experimental design. The definition and application of acceptance criteria (AC) for the validity of test runs is important for the setup and use of test methods, particularly for the use of new approach methods (NAM) in toxicity testing. AC can be used for decision rules on how to handle data, e.g., to accept the data for further use (AC fulfilled) or to reject the data (AC not fulfilled). The adherence to AC has important requirements and consequences that may seem surprising at first sight: (i) AC depend on a test method's objectives, e.g., on the types/concentrations of chemicals tested, the regulatory context, the desired throughput; (ii) AC are applied and documented at each test run, while validation of a method (including the definition of AC) is only performed once; (iii) if AC are altered, then the set of data produced by a method can change. AC, if missing, are the blind spot of quality assurance: Test results may not be reliable and comparable. The establishment and uses of AC will be further detailed in part II of this series.Toxicolog

Impact of culture conditions on the transcriptional levels of oxc gene and the oxalate consumption in Bifidobacterium

Oxalate is a highly toxic compound ubiquitous in the plant kingdom and widely consumed in human diet. A number of pathological conditions can arise from oxalate accumulation. Oxalate-degrading gut bacteria may play a key role in oxalate-related diseases by catabolizing free oxalate, reducing its plasmatic and urinary levels. Thirteen Bifidobacterium strains were screened for their ability to degrade oxalate by a rapid and sensitive method based on capillary electrophoresis (CE). A 100% oxalate degrading capacity was observed only for B. animalis subsp. lactis, a species widely used in dairy and pharmaceutical probiotic products. Putative oxalyl-CoA decarboxylase (oxc) and predicted permease genes were identified in B. lactis BI07, one of the most active strains. B. lactis BI07 consumption of oxalate and carbon sources was evaluated by CE analysis of the culture broths recovered from batch fermentation processes carried out in different growth conditions. Transcriptional analysis, using reverse transcription-quantitative PCR, along with the kinetics of oxalate degradation revealed that acidic conditions were a fundamental prerequisite for oxc transcription and enzyme activity

Modulation of gut microbiota by a synbiotic food

Diet is a major factor in maintaining a healthy gastrointestinal tract, and this has triggered the development of functional food containing probiotic and/or prebiotic components intended to improve the host\u2019s health via modulation of the gut microbiota. Molecular techniques based on the analysis of the rRNA gene sequences provide powerful tools to reveal the phylogenetic diversity of the microorganisms found in complex ecosystems, including the gut microbiota. In this study, we monitored the effects of a 30-days administration of a symbiotic food, containing Bifidobacterium longum, Lactobacilus helveticus and FOS, on the faecal microbiota of 20 healthy human subjects. For this purpose, PCR-DGGE analysis of 16S rRNA genes was used to detect possible changes in the overall bacterial composition. Cluster analysis of DGGE patterns highlighted that inter-individual differences were higher than the differences detected among the time-points of the feeding study. Statistical and Principal Component Analyses of the DGGE band intensities showed that the symbiotic consumption did not significantly alter the bacterial communities structure, suggesting a stabilizing impact on the microbiota. Subsequent analysis with real-time PCR indicated an increase in the amounts of B. longum and L. helveticus species, suggesting the capability of these probiotic strains to colonize the gut ecosystem

Development of a LDR-Universal array platform for the phylogenetic fingerprint of the Human Intestinal Microbiota

Human beings are superorganisms in co-evolution with their own intestinal microbiota. Throughout an extensive microbial-mammalian co-metabolism, the intestinal microbiota affects a broad range of physiological features of the human host and contributes to health and well being. The vast majority of the bacteria represented in the human intestinal microbiota belongs only to few bacteria phyla: Firmicutes, Bacteroidetes, Actinobacteria, Proteobacteria, and Fusobactera. However, at lower taxonomic levels, the intestinal microbiota is highly diverse. 1200 different phylotypes have been described, and each person\u2019s gut microbiome is characterized by a peculiar phylotypes complement. Because of a high degree of functional redundancy between the different phylotypes, such diversity is not related to function, and, at the functional level, individuals share an extensive identifiable core microbiome. Division-wide changes in microbiota composition can cause deviations from such functional core microbiome and seriously impact the host physiological state. In order to monitor the microbiota imbalances towards a potential pathobiota community, a specific Ligase Detection Reaction \u2013 Universal Array (LDR-UA) platform was developed. Cluster, family and genus-specific probes were specifically designed to obtain a microbiota phylogenetic fingerprint for the principal bacterial groups which define the core functional microbiome. Species-specific probes were added to detect targets of particular interest, such as probiotic bacteria and enteropathogens. The complex set of LDR probes was developed on the basis of discriminating positions within 16S rRNA gene. A total of 28 ATCC and DSM strains, and 2 isolates, were tested with very good specificity and efficiency. Pilot microarray experiments have been carried out on faecal samples isolated from adults and elderly volunteers. A reproducible microbiota fingerprint has been obtained from 5 subjects for each class