17 research outputs found
Simultaneous microbeam IBA and beam-induced luminescence analysis of strained doped silica fibre radiation dosimeters
Get PDFWe demonstrate that the simultaneous combination of ion beam analysis (IBA) and ion beam induced luminescence (IL) can reveal valuable information concerning the performance of strained doped silica fibre thermoluminescence microdosimeters. The micron scale spatial resolution and low detection limits of IBA allow the lateral distribution of dopant elements to be mapped and then correlated with the distribution of prompt radioluminescence. Measurement of the decay of the IL signal with dose provide information concerning the saturation of the subsequent TL signal at high doses. MeV ion beams can deposit relatively high energy in localized, well-quantified small volumes and so this method is valuable for studying high dose effects in TL dosimeters. We describe a simple modification of the target chamber microscope which enables sensitive low background light detection in two wavelength bands and present preliminary results from three types of germanium doped silica fibre dosimeter
Correlative imaging of trace elements and intact molecular species in a single-tissue sample at the 50 μm scale
Get PDFElemental and molecular imaging play a crucial role in understanding disease pathogenesis. To accurately correlate elemental and molecular markers, it is desirable to perform sequential elemental and molecular imaging on a single-tissue section. However, very little is known about the impact of performing these measurements in sequence. In this work, we highlight some of the challenges and successes associated with performing elemental mapping in sequence with mass spectrometry imaging. Specifically, the feasibility of molecular mapping using the mass spectrometry imaging (MSI) techniques matrix-assisted laser desorption ionization (MALDI) and desorption electrospray ionization (DESI) in sequence with the elemental mapping technique particle-induced X-ray emission (PIXE) is explored. Challenges for integration include substrate compatibility, as well as delocalization and spectral changes. We demonstrate that while sequential imaging comes with some compromises, sequential DESI-PIXE imaging is sufficient to correlate sulfur, iron, and lipid markers in a single tissue section at the 50 μm scale
Fabrication of three-dimensional SU-8 microchannels by proton beam writing for microfluidics applications: Fluid flow characterisation
No full textThe proton beam writing (PBW) technique was used to fabricate microfluidic structures in SU-8 resist. A network of the buried channels was fabricated as part of a project to develop functional microfluidic device for neuronal studies and self-powered microfluidics. Protons with energies between 2.5 MeV and 0.75 MeV were used to fabricate the buried channels with a minimum feature size of around 1 μm and depths of 40–55 μm. Roughness of channels sidewalls was around 2.5 nm rms. Exposure regime and examples of functional networks fabricated using PBW are described. COMSOL Multiphysics® software was used to model the flow characteristics of fluid in the SU-8 microchannels structured by PBW. The results obtained using PBW are compared with the structures fabricated by UV-lithography
Direct quantification of rare earth doped titania nanoparticles in individual human cells
No full textThere are many possible biomedical applications for titania nanoparticles (NPs) doped with rare earth elements (REEs), from dose enhancement and diagnostic imaging in radiotherapy, to biosensing. However, there are concerns that the NPs could disintegrate in the body thus releasing toxic REE ions to undesired locations. As a first step, we investigate how accurately the Ti/REE ratio from the NPs can be measured inside human cells. A quantitative analysis of whole, unsectioned, individual human cells was performed using proton microprobe elemental microscopy. This method is unique in being able to quantitatively analyse all the elements in an unsectioned individual cell with micron resolution, while also scanning large fields of view. We compared the Ti/REE signal inside cells to NPs that were outside the cells, non-specifically absorbed onto the polypropylene substrate. We show that the REE signal in individual cells co-localises with the titanium signal, indicating that the NPs have remained intact. Within the uncertainty of the measurement, there is no difference between the Ti/REE ratio inside and outside the cells. Interestingly, we also show that there is considerable variation in the uptake of the NPs from cell-to-cell, by a factor of more than 10. We conclude that the NPs enter the cells and remain intact. The large heterogeneity in NP concentrations from cell-to-cell should be considered if they are to be used therapeutically
Fabrication of three-dimensional SU-8 microchannels by proton beam writing for microfluidics applications: Fluid flow characterisation
Get PDFThe proton beam writing (PBW) technique was used to fabricate microfluidic structures in SU-8 resist. A network of the buried channels was fabricated as part of a project to develop functional microfluidic device for neuronal studies and self-powered microfluidics. Protons with energies between 2.5 MeV and 0.75 MeV were used to fabricate the buried channels with a minimum feature size of around 1 μm and depths of 40–55 μm. Roughness of channels sidewalls was around 2.5 nm rms. Exposure regime and examples of functional networks fabricated using PBW are described. COMSOL Multiphysics® software was used to model the flow characteristics of fluid in the SU-8 microchannels structured by PBW. The results obtained using PBW are compared with the structures fabricated by UV-lithography
Optimisation of secondary ion transport in ambient pressure MeV SIMS
No full textAmbient Pressure MeV SIMS (AP MeV SIMS) is a special application of MeV SIMS technique for molecular detection and imaging under ambient conditions. There are several advantages of using ambient over nonambient techniques such as minimising or completely avoiding sample preparation that can contribute to the reducing of costs and shortening of analysis. Moreover, by performing analysis in ambient conditions negative vacuum influence on samples will be avoided. The emergence of ambient mass spectrometry techniques over the
past decade has been enormous with a broad range of applications such as food quality, environmental analysis and life sciences [1,2]. On the other hand, the disadvantage of ambient pressure mass spectrometry techniques is the influence of the ambient background which can suppress the signal from the target. In AP MeV SIMS, molecular species present in ambient surrounding of the sampling site will also be ionised by ion beams hence secondary ions originating from the sample have to be transported in the most efficient manner from the site of
interaction of ion beams and target into the mass spectrometer capillary and, finally, into the mass spectrometer [3]. In this work, we present the optimisation of the mass spectrometer capillary temperature, distances of mass spectrometer and sheath gas, in our case helium, with respect to the beam axis and angle of the helium flow capillary with respect to the sample
Rapid, secure drug testing using fingerprint development and paper spray mass spectrometry
No full textBACKGROUND: Paper spray mass spectrometry6 is a technique that has recently emerged and has shown excellent analytical sensitivity to a number of drugs in blood. As an alternative to blood, fingerprints have been shown to provide a noninvasive and traceable sampling matrix. Our goal was to validate the use of fingerprint samples to detect cocaine use. METHODS: Samples were collected on triangular pieces (168 mm2) of washed Whatman Grade I chromatography paper. Following application of internal standard, spray solvent and a voltage were applied to the paper before mass spectrometry detection. A fingerprint visualization step was incorporated into the analysis procedure by addition of silver nitrate solution and exposing the sample to ultraviolet light. RESULTS: Limits of detection for cocaine, benzoylecgonine, and methylecgonine were 1, 2, and 31 ng/mL respectively, with relative standard deviations of less than 33%. No matrix effects were observed. Analysis of 239 fingerprint samples yielded a 99% true-positive rate and a 2.5% false-positive rate, based on the detection of cocaine, benzoylecgonine, or methylecgonine with use of a single fingerprint. CONCLUSIONS: The method offers a qualitative and noninvasive screening test for cocaine use. The analysis method developed is rapid (4 min/sample) and requires no sample preparation.</p
Exploring a route to a selective and sensitive portable system for explosive detection– swab spray ionisation coupled to of high-field assisted waveform ion mobility spectrometry (FAIMS)
Get PDFPaper spray mass spectrometry is a rapid and sensitive tool for explosives detection but has so far only been demonstrated using high resolution mass spectrometry, which bears too high a cost for many practical applications. Here we explore the potential for paper spray to be implemented in field applications with portable mass spectrometry. This involved (a) replacing the paper substrate with a swabbing material (which we call “swab spray”) for compatibility with standard collection materials; (b) collection of explosives from surfaces; (c) an exploration of interferences within a ± 0.5 m/z window; and (d) demonstration of the use of high-field assisted waveform ion mobility spectrometer (FAIMS) for enhanced selectivity. We show that paper and Nomex® are viable collection materials, with Nomex providing cleaner spectra and therefore greater potential for integration with portable mass spectrometers. We show that sensitive detection using swab spray will require a mass spectrometer with a mass resolving power of 4000 or more. We show that by coupling the swab spray ionisation source with FAIMS, it is possible to reduce background interferences, thereby facilitating the use of a low resolving power (e.g. quadrupole) mass spectrometer
Rapid, secure drug testing using fingerprint development and paper spray mass spectrometry
Get PDFBACKGROUND: Paper spray mass spectrometry6 is a technique
that has recently emerged and has shown excellent
analytical sensitivity to a number of drugs in blood. As an
alternative to blood, fingerprints have been shown to
provide a noninvasive and traceable sampling matrix.
Our goal was to validate the use of fingerprint samples to
detect cocaine use.
METHODS: Samples were collected on triangular pieces
(168 mm2) of washed Whatman Grade I chromatography
paper. Following application of internal standard,
spray solvent and a voltage were applied to the paper
before mass spectrometry detection. A fingerprint visualization
step was incorporated into the analysis procedure
by addition of silver nitrate solution and exposing the
sample to ultraviolet light.
RESULTS: Limits of detection for cocaine, benzoylecgonine,
and methylecgonine were 1, 2, and 31 ng/mL respectively,
with relative standard deviations of less than 33%. No
matrix effects were observed. Analysis of 239 fingerprint
samples yielded a 99% true-positive rate and a 2.5%
false-positive rate, based on the detection of cocaine,
benzoylecgonine, or methylecgonine with use of a single
fingerprint.
CONCLUSIONS: The method offers a qualitative and noninvasive
screening test for cocaine use. The analysis
method developed is rapid (4 min/sample) and requires
no sample preparation.</p
Exploring Rapid, Sensitive and Reliable Detection of Trace Explosives Using Paper Spray Mass Spectrometry (PS‐MS)
Get PDFIn this publication we work towards providing fast, sensitive and selective analysis of explosive compounds collected on swabs using paper spray mass spectrometry. We have (a) increased the size of the paper spray substrate to 1.6×2.1 cm for compatibility with current practise
in swabbing for explosive material; (b) developed a method for determining a successful extraction of analyte from the substrate to reduce false negative events; and (c) expanded the range of analytes that can be detected using paper spray to include the peroxide explosive HMTD, as well as nitroglycerine (NG), picric acid (PA) and tetryl. We report the development of a 30 s method for the simultaneous
detection of 7 different explosive materials using PSMS with detection limits below 25 pg, as well as detection of HMTD at 2500 pg, showing an improvement on previously published work
