Acoustically controlled enhancement of molecular sensing to assess oxidative stress in cells

We demonstrate a microfluidic platform for the controlled aggregation of colloidal silver nanoparticles using surface acoustic waves (SAWs), enabling surface enhanced Raman scattering (SERS) analysis of a cell based model for oxidative damage. We show that by varying the frequency and the power of the acoustic energy, it is possible to modulate the aggregation of the colloid within the sample and hence to optimise the SERS analysis

On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)

Velocity-space sensitivity of the time-of-flight neutron spectrometer at JET

The velocity-space sensitivities of fast-ion diagnostics are often described by so-called weight functions. Recently, we formulated weight functions showing the velocity-space sensitivity of the often dominant beam-target part of neutron energy spectra. These weight functions for neutron emission spectrometry (NES) are independent of the particular NES diagnostic. Here we apply these NES weight functions to the time-of-flight spectrometer TOFOR at JET. By taking the instrumental response function of TOFOR into account, we calculate time-of-flight NES weight functions that enable us to directly determine the velocity-space sensitivity of a given part of a measured time-of-flight spectrum from TOFOR

Relationship of edge localized mode burst times with divertor flux loop signal phase in JET

A phase relationship is identified between sequential edge localized modes (ELMs) occurrence times in a set of H-mode tokamak plasmas to the voltage measured in full flux azimuthal loops in the divertor region. We focus on plasmas in the Joint European Torus where a steady H-mode is sustained over several seconds, during which ELMs are observed in the Be II emission at the divertor. The ELMs analysed arise from intrinsic ELMing, in that there is no deliberate intent to control the ELMing process by external means. We use ELM timings derived from the Be II signal to perform direct time domain analysis of the full flux loop VLD2 and VLD3 signals, which provide a high cadence global measurement proportional to the voltage induced by changes in poloidal magnetic flux. Specifically, we examine how the time interval between pairs of successive ELMs is linked to the time-evolving phase of the full flux loop signals. Each ELM produces a clear early pulse in the full flux loop signals, whose peak time is used to condition our analysis. The arrival time of the following ELM, relative to this pulse, is found to fall into one of two categories: (i) prompt ELMs, which are directly paced by the initial response seen in the flux loop signals; and (ii) all other ELMs, which occur after the initial response of the full flux loop signals has decayed in amplitude. The times at which ELMs in category (ii) occur, relative to the first ELM of the pair, are clustered at times when the instantaneous phase of the full flux loop signal is close to its value at the time of the first ELM

Intracellular multiplex detection and imaging of stable chemisorbed labels by SERS spectroscopy

SERS spectroscopy is currently gaining wider acceptance in biological research due to its ability to obtain signals from very low quantities of material, and to obtain information from within live cells. SERS spectroscopy yields very narrow bands (10-100 times narrower than typical fluorescence bands) and spectra suffer from minimal interference from aqueous media, making SERS spectroscopy ideal for multiplex detection of intracellular components. Typically for sensing, nanoparticles are labelled with suitable sensing molecules such as a dye or thiol. Nanoparticle labelling involves two different types of interaction between the label and the enhancing surface, chemisorption and physisorption. The former is considerably stronger and more stable than the latter and hence chemisorbed labels are more appropriate for intracellular nanosensor design. In this paper, we demonstrate the difference in stability of both types of Raman label inside live cells over periods of time. Chinese hamster ovary (CHO) cells were infused with a mixture of differently labelled stable nanosensors and were imaged using SERS microspectroscopy. We also demonstrate the applicability of SERS mapping for high-throughput multiplex detection using micropatterned cell arrays

Monitoring the uptake and redistribution of metal nanoparticles during cell culture using surface-enhanced raman scattering spectroscopy

We describe the uptake of silver nanoparticles by CHO (Chinese hamster ovary) cells and their subsequent fate as a result of cell division during culture, as monitored by surface-enhanced Raman scattering (SERS) spectroscopy. Mapping of populations of cells containing both labeled and native nanoparticles by SERS spectroscopy imaging provided a quantitative method by which the number of intracellular nanoparticles could be monitored. Initially, for a given amount of nanoparticles, the relationship between the number taken up into the cell and the time of incubation was explored. Subsequently, the redistribution of intracellular nanoparticles upon multiple rounds of cell division was investigated. Intracellular SERS signatures remained detectable in the cells for up to four generations, although the abundance and intensity of the signals declined rapidly as nanoparticles were shared with daughter cells. The intensity of the SERS signal was dependent both on stability of the label and their abundance (nanoparticle aggregation increases the extent of the SERS enhancement). The data show that while the labeled nanoparticles remain stable for prolonged periods, during cell division, the changes in signal could be attributed both to a decrease in abundance and distribution (and hence aggregation

SERS mapping of nanoparticle labels in single cells using a microfluidic chip

We report for the first time the time-resolved mapping of intracellular nanoparticle labels from within living cells retained in a microstructured trap using Raman spectroscopy. The methods employed here also demonstrate the ability to rapidly discriminate between cell populations containing different SERS labels

Structure and behaviour of proteins and viruses from Raman optical activity

No abstract available

Characterization of individual microdroplets by SERRS spectroscopy

Raman spectroscopy and its various derivatives continue to offer the analyst fast, powerful, non-invasive and nondestructive means by which to identify multiple analytes simultaneously and in real time. By virtue of the huge enhancements possible in Raman scattering, generated by both surface enhancement and the resonance Raman effect, or when coupled with other techniques such as confocal microscopy, Raman spectroscopy is becoming more and more applicable to the types of assay being conducted in lab-on-a-chip applications, such as flow cytometry, cell patterning and trapping, and microarrays, all of which often involve the detection of extremely low quantities of analyte. Surface enhanced Raman scattering (SERS, or when coupled with the resonance Raman phenomenon, SERRS) spectroscopy has proven to be of particular use as a robust optical detection method in microfluidic environments. In this paper, we demonstrate the use of SERRS multiplex detection to quantitatively characterize individual microdroplets in a continuous stream whose contents are gradually varied using a bespoke pump control algorithm

New insight into solution structure and dynamics of proteins, nucleic acids, and viruses from Raman optical activity

Raman optical activity measures vibrational optical activity by means of a small difference in the intensity of Raman scattering from chiral molecules in right and left circularly polarized incident light. The sensitivity of ROA to chirality makes it an incisive probe of biomolecular structure and dynamics in aqueous solution. This article reviews the basic theory and instrumentation of ROA, and describes recent results which illustrate how ROA provides new insight into current biomedical problems including protein misfolding and disease, and virus structure at the molecular level