مجال
التميز
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تميز دراسي وبحثي
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البحوث المنشورة
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البحث (1):
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عنوان البحث:
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Combining Raman and FT-IR Spectroscopy with
Quantitative Isotopic Labeling for Differentiation of E. coli Cells at
Community and Single Cell Levels
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رابط إلى البحث:
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Click Here
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تاريخ النشر:
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1st April 2015
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موجز عن البحث:
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There
is no doubt that the contribution of microbially mediated bioprocesses toward
maintenance of life on earth is vital. However, understanding these microbes
in situ is currently a bottleneck, as most methods require culturing these
microorganisms to suitable biomass levels so that their phenotype can be
measured. The development of new culture-independent strategies such as
stable isotope probing (SIP) coupled with molecular biology has been a
breakthrough toward linking gene to function, while circumventing in vitro
culturing. In this study, for the first time we have combined Raman
spectroscopy and Fourier transform infrared (FT-IR) spectroscopy, as
metabolic fingerprinting approaches, with SIP to demonstrate the quantitative
labeling and differentiation of Escherichia coli cells. E. coli cells were
grown in minimal medium with fixed final concentrations of carbon and
nitrogen supply, but with different ratios and combinations of 13C/12C
glucose and 15N/14N ammonium chloride, as the sole carbon and nitrogen
sources, respectively. The cells were collected at stationary phase and
examined by Raman and FT-IR spectroscopies. The multivariate analysis
investigation of FT-IR and Raman data illustrated unique clustering patterns
resulting from specific spectral shifts upon the incorporation of different
isotopes, which were directly correlated with the ratio of the isotopically
labeled content of the medium. Multivariate analysis results of single-cell
Raman spectra followed the same trend, exhibiting a separation between E.
coli cells labeled with different isotopes and multiple isotope levels of C
and N.
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البحث (2):
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عنوان البحث:
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Chicken,
beams, and Campylobacter: rapid differentiation of foodborne bacteria via
vibrational spectroscopy and MALDI-mass spectrometry
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رابط إلى البحث:
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Here
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تاريخ النشر:
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26 Oct 2015
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موجز عن البحث:
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Campylobacter species are one of the main causes of
food poisoning worldwide. Despite the availability of established culturing
and molecular techniques, due to the fastidious nature of these
microorganisms, simultaneous detection and species differentiation still
remains challenging. This study focused on the differentiation of eleven
Campylobacter strains from six species, using Fourier transform infrared
(FT-IR) and Raman spectroscopies, together with matrix-assisted laser
desorption ionisation-time of flight-mass spectrometry (MALDI-TOF-MS), as
physicochemical approaches for generating biochemical fingerprints. Cluster
analysis of data from each of the three analytical approaches provided clear
differentiation of each Campylobacter species, which was generally in
agreement with a phylogenetic tree based on 16S rRNA gene sequences. Notably,
although C. fetus subspecies fetus and venerealis are phylogenetically very
closely related, using FT-IR and MALDI-TOF-MS data these subspecies were
readily differentiated based on differences in the lipid (2920 and 2851 cm−1)
and fingerprint regions (1500–500 cm−1) of the FT-IR spectra, and the
500–2000 m/z region of the MALDI-TOF-MS data. A finding that was further
investigated with targeted lipidomics using liquid chromatography-mass
spectrometry (LC-MS). Our results demonstrate that such metabolomics
approaches combined with molecular biology techniques may provide critical
information and knowledge related to the risk factors, virulence, and
understanding of the distribution and transmission routes associated with
different strains of foodborne Campylobacter spp.
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البحث (3):
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عنوان البحث:
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Rapid,
accurate, and comparative differentiation of clinically and industrially
relevant microorganisms via multiple vibrational spectroscopic fingerprinting
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رابط إلى البحث:
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Here
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تاريخ النشر:
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07 Jul 2016
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موجز عن البحث:
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Despite the fact that various microorganisms (e.g.,
bacteria, fungi, viruses, etc.) have been linked with infectious diseases,
their crucial role towards sustaining life on Earth is undeniable. The huge
biodiversity, combined with the wide range of biochemical capabilities of
these organisms, have always been the driving force behind their large number
of current, and, as of yet, undiscovered future applications. The presence of
such diversity could be said to expedite the need for the development of
rapid, accurate and sensitive techniques which allow for the detection,
differentiation, identification and classification of such organisms. In this
study, we employed Fourier transform infrared (FT-IR), Raman, and surface
enhanced Raman scattering (SERS) spectroscopies, as molecular whole-organism
fingerprinting techniques, combined with multivariate statistical analysis
approaches for the classification of a range of industrial, environmental or
clinically relevant bacteria (P. aeruginosa, P. putida, E. coli, E. faecium,
S. lividans, B. subtilis, B. cereus) and yeast (S. cerevisiae). Principal
components-discriminant function analysis (PC-DFA) scores plots of the
spectral data collected from all three techniques allowed for the clear
differentiation of all the samples down to sub-species level. The partial
least squares-discriminant analysis (PLS-DA) models generated using the SERS
spectral data displayed lower accuracy (74.9%) when compared to those
obtained from conventional Raman (97.8%) and FT-IR (96.2%) analyses. In
addition, whilst background fluorescence was detected in Raman spectra for S.
cerevisiae, this fluorescence was quenched when applying SERS to the same
species, and conversely SERS appeared to introduce strong fluorescence when
analysing P. putida. It is also worth noting that FT-IR analysis provided
spectral data of high quality and reproducibility for the whole sample set,
suggesting its applicability to a wider range of samples, and perhaps the
most suitable for the analysis of mixed cultures in future studies.
Furthermore, our results suggest that while each of these spectroscopic
approaches may favour different organisms (sample types), when combined, they
would provide complementary and more in-depth knowledge (structural and/or
metabolic state) of biological systems. To the best of our knowledge, this is
the first time that such a comparative and combined spectroscopic study
(using FT-IR, Raman and SERS) has been carried out on microbial samples.
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البحث (4):
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عنوان البحث:
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Rapid, Accurate,
and Quantitative Detection of Propranolol in Multiple Human Biofluids via
Surface-Enhanced Raman Scattering
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رابط إلى البحث:
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Click Here
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تاريخ النشر:
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12 October
2016
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موجز عن البحث:
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There has been an increasing demand for rapid and
sensitive techniques for the identification and quantification of
pharmaceutical compounds in human biofluids during the past few decades, and
surface-enhanced Raman scattering (SERS) is one of a number of physicochemical
techniques with the potential to meet these demands. In this study we have
developed a SERS-based analytical approach for the assessment of human
biofluids in combination with chemometrics. This novel approach has enabled
the detection and quantification of the β-blocker propranolol spiked into
human serum, plasma, and urine at physiologically relevant concentrations. A
range of multivariate statistical analysis techniques, including principal
component analysis (PCA), principal component–discriminant function analysis
(PC-DFA) and partial least-squares regression (PLSR) were employed to
investigate the relationship between the full SERS spectral data and the
level of propranolol. The SERS spectra when combined with PCA and PC-DFA
demonstrated clear differentiation of neat biofluids and biofluids spiked
with varying concentrations of propranolol ranging from 0 to 120 μM, and
clear trends in ordination scores space could be correlated with the level of
propranolol. Since PCA and PC-DFA are categorical classifiers, PLSR modeling
was subsequently used to provide accurate propranolol quantification within
all biofluids with high prediction accuracy (expressed as root-mean-square
error of predictions) of 0.58, 9.68, and 1.69 for serum, plasma, and urine
respectively, and these models also had excellent linearity for the training
and test sets between 0 and 120 μM. The limit of detection as calculated from
the area under the naphthalene ring vibration from propranolol was 133.1
ng/mL (0.45 μM), 156.8 ng/mL (0.53 μM), and 168.6 ng/mL (0.57 μM) for serum,
plasma, and urine, respectively. This result shows a consistent signal
irrespective of biofluid, and all are well within the expected physiological
level of this drug during therapy. The results of this study demonstrate the
potential of SERS application as a diagnostic screening method, following
further validation and optimization to improve detection of pharmaceutical
compounds and quantification in human biofluids, which may open up new
exciting opportunities for future use in various biomedical and forensic
applications.
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البحث (5):
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عنوان البحث:
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Quantitative
detection of codeine in human plasma using surface-enhanced Raman scattering
via adaptation of the isotopic labelling principle
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رابط إلى البحث:
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Click
Here
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تاريخ النشر:
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02 Mar
2017
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موجز عن البحث:
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In this study surface enhanced Raman scattering
(SERS) combined with the isotopic labelling (IL) principle has been used for
the quantification of codeine spiked into both water and human plasma.
Multivariate statistical approaches were employed for the analysis of these
SERS spectral data, particularly partial least squares regression (PLSR)
which was used to generate models using the full SERS spectral data for
quantification of codeine with, and without, an internal isotopic labelled
standard. The PLSR models provided accurate codeine quantification in water
and human plasma with high prediction accuracy (Q2). In addition, the
employment of codeine-d6 as the internal standard further improved the
accuracy of the model, by increasing the Q2 from 0.89 to 0.94 and decreasing
the low root-mean-square error of predictions (RMSEP) from 11.36 to 8.44.
Using the peak area at 1281 cm−1 assigned to C–N stretching, C–H wagging and
ring breathing, the limit of detection was calculated in both water and human
plasma to be 0.7 μM (209.55 ng mL−1) and 1.39 μM (416.12 ng mL−1),
respectively. Due to a lack of definitive codeine vibrational assignments,
density functional theory (DFT) calculations have also been used to assign
the spectral bands with their corresponding vibrational modes, which were in
excellent agreement with our experimental Raman and SERS findings. Thus, we
have successfully demonstrated the application of SERS with isotope labelling
for the absolute quantification of codeine in human plasma for the first time
with a high degree of accuracy and reproducibility. The use of the IL
principle which employs an isotopolog (that is to say, a molecule which is
only different by the substitution of atoms by isotopes) improves
quantification and reproducibility because the competition of the codeine and
codeine-d6 for the metal surface used for SERS is equal and this will offset
any difference in the number of particles under analysis or any fluctuations
in laser fluence. It is our belief that this may open up new exciting
opportunities for testing SERS in real-world samples and applications which
would be an area of potential future studies.
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البحث (6):
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عنوان البحث:
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Quantitative Online
Liquid Chromatography–Surface-Enhanced Raman Scattering (LC-SERS) of Methotrexate
and its Major Metabolites
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رابط إلى البحث:
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Click Here
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تاريخ النشر:
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15 May
2017
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موجز عن البحث:
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The application of Raman spectroscopy as a detection
method coupled with liquid chromatography (LC) has recently attracted
considerable interest, although this has currently been limited to isocratic
elution. The combination of LC with rapidly advancing Raman techniques, such
as surface-enhanced Raman scattering (SERS), allows for rapid separation,
identification and quantification, leading to quantitative discrimination of
closely eluting analytes. This study has demonstrated the utility of SERS in
conjunction with reversed-phase liquid chromatography (RP-LC), for the
detection and quantification of the therapeutically relevant drug molecule
methotrexate (MTX) and its metabolites 7-hydroxy methotrexate (7-OH MTX) and
2,4-diamino-N(10)-methylpteroic acid (DAMPA) in pure solutions and mixtures,
including spikes into human urine from a healthy individual and patients
under medication. While the RP-LC analysis developed employed gradient
elution, where the chemical constituents of the mobile phase were modified stepwise
during analysis, this did not overtly interfere with the SERS signals. In
addition, the practicability and clinical utility of this approach has also
been demonstrated using authentic patients’ urine samples. Here, the
identification of MTX, 7-OH MTX and DAMPA are based on their unique SERS
spectra, providing limits of detection of 2.36, 1.84, and 3.26 μM
respectively. Although these analytes are amenable to LC and LC-MS detection
an additional major benefit of the SERS approach is its applicability toward
the detection of analytes that do not show UV absorption or are not ionised
for mass spectrometry (MS)-based detection. The results of this study clearly
demonstrate the potential application of online LC-SERS analysis for
real-time high-throughput detection of drugs and their related metabolites in
human biofluids.
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المؤتمرات العلمية:
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المؤتمر (1):
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عنوان المؤتمر:
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Infrared & Raman Discussion Group
(IRDG) meeting
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تاريخ الإنعقاد:
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18/12/2014
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مكان
الإنعقاد:
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London, UK
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طبيعة المشاركة:
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Poster Presentation
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عنوان المشاركة:
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Rapid, Accurate, and Quantitative Detection
of Propranolol in Multiple Human Biofluids via Surface-Enhanced Raman
Scattering
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ملخص المشاركة:
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There
has been an increasing demand for rapid and sensitive techniques for the
identification and quantification of pharmaceutical compounds in human
biofluids during the past few decades, and surface-enhanced Raman scattering
(SERS) is one of a number of physicochemical techniques with the potential to
meet these demands. In this study we have developed a SERS-based analytical
approach for the assessment of human biofluids in combination with
chemometrics. This novel approach has enabled the detection and quantification
of the β-blocker propranolol spiked into human serum, plasma, and urine at
physiologically relevant concentrations. A range of multivariate statistical
analysis techniques, including principal component analysis (PCA), principal
component–discriminant function analysis (PC-DFA) and partial least-squares
regression (PLSR) were employed to investigate the relationship between the
full SERS spectral data and the level of propranolol. The SERS spectra when
combined with PCA and PC-DFA demonstrated clear differentiation of neat
biofluids and biofluids spiked with varying concentrations of propranolol
ranging from 0 to 120 μM, and clear trends in ordination scores space could
be correlated with the level of propranolol. Since PCA and PC-DFA are categorical
classifiers, PLSR modeling was subsequently used to provide accurate
propranolol quantification within all biofluids with high prediction accuracy
(expressed as root-mean-square error of predictions) of 0.58, 9.68, and 1.69
for serum, plasma, and urine respectively, and these models also had
excellent linearity for the training and test sets between 0 and 120 μM. The
limit of detection as calculated from the area under the naphthalene ring
vibration from propranolol was 133.1 ng/mL (0.45 μM), 156.8 ng/mL (0.53 μM),
and 168.6 ng/mL (0.57 μM) for serum, plasma, and urine, respectively. This
result shows a consistent signal irrespective of biofluid, and all are well
within the expected physiological level of this drug during therapy. The
results of this study demonstrate the potential of SERS application as a
diagnostic screening method, following further validation and optimization to
improve detection of pharmaceutical compounds and quantification in human
biofluids, which may open up new exciting opportunities for future use in
various biomedical and forensic applications.
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المؤتمر (2):
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عنوان المؤتمر:
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The 8th Saudi Student Conference
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تاريخ الإنعقاد:
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31 Jan – 01 Feb 2015
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مكان
الإنعقاد:
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London, UK
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طبيعة المشاركة:
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Poster Presentation
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عنوان المشاركة:
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Isotope labelling for improved quantitative
surface-enhanced Raman scattering: application to detection of tryptophan and
caffeine
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ملخص المشاركة:
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Raman
spectroscopy has attracted considerable interest during the past two decades
as a vibrational technique used for the molecular characterisation of
different molecules. However, the Raman effect is known to be generally weak,
which can be greatly improved using surface enhanced Raman scattering (SERS).
In recent years, the power of SERS for rapid identification and
quantification of target analytes in a wide range of applications has been
demonstrated in multiple studies. The application of SERS in combination with
an isotopically labelled compound (ILC), as internal standard, has shown
promising results for quantitative SERS measurements, by improving both its
accuracy and precision. This is because the 12C and 13C
or 1H and 2H (D) labelled molecules will compete
equally for the metal surface. Thereby the use of these internal standards
will result in the reduction of any influences due to the number of
nanoparticles within the analysis zone and fluctuations in laser fluence.
Thus, in this study we have employed SERS for quantitative detection of
tryptophan (Trp) and caffeine. These have been chosen because Trp is readily
available as the deuterated form and caffeine is available in both 12C
and 13C. This allows assessment of the different types of isotopes
as internal standards. Quantum chemical calculations based on density
functional theory (DFT) have been utilized to determine the vibrational
characteristics of the target analytes. For SERS analysis incorporating
isotopologues of tryptophan three independent experiments were conducted with
three different batches of nanoparticles over a 12 month period; our results
show that the use of this internal standard improves quantification of this
target molecule. Our results
demonstrate the potential application of this approach combined with SERS for
the quantitative detection of Trp and caffeine and we believe this could be
readily extended to other biologically-relevant compounds.
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