This blog has been set up for editors, reviewers, authors and readers of Elsevier's Analytical Chemistry Journals - all of which can be seen below. It will be updated from Monday to Friday with general news and announcements concerning the titles listed on this page. It should be noted that the views or claims made in the news items and feeds are not necessarily those of the Publisher.
World Congress on Biosensors 2014
Biosensors 2014
Tuesday 22 January 2013
A new issue of this journal has just
been published. To see abstracts of the papers it contains (with links through
to the full papers) click here:
Oxidative stress
is associated with several pathologies like cardiovascular, neurodegenerative,
cancer and even aging. It has been suggested that a diet rich in antioxidants
would be beneficial to human health and a lot of interest is focused on the
determination of antioxidant capacity of natural products. Different chemical
methods have been developed including the popular ORAC that evaluates the
potential of a sample as inhibitor of a target molecule oxidation.
Chemical-based methods are useful for screening, they are low cost,
high-throughput and yield an index value (expressed as equivalents of Trolox)
that allows comparing and ordering different products. More recently,
nanoparticles-based assays have been developed to sense the antioxidant power of
natural products. However, the antioxidant capacity indexes obtained by chemical
assays cannot extrapolate the performance of the sample in vivo. Considering
that antioxidant action is not limited to scavenging free radicals but includes
upregulation of antioxidant and detoxifying enzymes, modulation of redox cell
signaling and gene expression, it is necessary to move to cellular assays in
order to evaluate the potential antioxidant activity of a compound or extract.
Animal models and human studies are more appropriate but also more expensive and
time-consuming, making the cell culture assays very attractive as intermediate
testing methods. Cellular antioxidant activity (CAA) assays, activation of redox
transcription factors, inhibition of oxidases or activation of antioxidant
enzymes are reviewed and compared with the classical in vitro chemical-based
assays for evaluation of antioxidant capacity of natural products.
Graphical abstract
Highlights
► There is high interest
on determination of antioxidant capacity of natural products. ► Several chemical
in vitro methods should be used. ► Cellular antioxidant activity assays should
also be performed. ► No strong correlation between chemical and cellular
assays.
This paper
presents the development of a non-aqueous capillary electrophoresis method
coupled to UV detection combined with multivariate curve resolution-alternating
least-squares (MCR-ALS) to carry out the resolution and quantitation of a
mixture of six phenolic acids in virgin olive oil samples. p-Coumaric, caffeic,
ferulic, 3,4-dihydroxyphenylacetic, vanillic and 4-hydroxyphenilacetic acids
have been the analytes under study. All of them present different absorption
spectra and overlapped time profiles with the olive oil matrix interferences and
between them. The modeling strategy involves the building of a single MCR-ALS
model composed of matrices augmented in the temporal mode, namely spectra remain
invariant while time profiles may change from sample to sample. So MCR-ALS was
used to cope with the coeluting interferences, on accounting the second order
advantage inherent to this algorithm which, in addition, is able to handle data
sets deviating from trilinearity, like the data herein analyzed. The method was
firstly applied to resolve standard mixtures of the analytes randomly prepared
in 1-propanol and, secondly, in real virgin olive oil samples, getting recovery
values near to 100% in all cases. The importance and novelty of this methodology
relies on the combination of non-aqueous capillary electrophoresis second-order
data and MCR-ALS algorithm which allows performing the resolution of these
compounds simplifying the previous sample pretreatment stages.
Graphical abstract
Highlights
► Novel combination of
NACE and MCR-ALS for determination of phenolic acids in EVOO. ► Good results are
achieved in less time than other CE method for these compounds. ► Resolution and
quantitation without to be necessary a complex experimental
work.
Herein, highly
efficient solid-state ECL sensor was introduced for the first time onto the
screen printed electrodes of the paper-based chips (PCs) based on the composite
film of poly(sodium 4-styrenesulfonate) functionalized graphene (PSSG) and
Nafion. Attributed to the cooperative characteristics of both PSS and graphene,
PSSG ensured both effective Ru(bpy)3 2+ immobilization and fast
electron transfer of Ru(bpy)3 2+ in the composite film. The ECL
behaviors at the developed sensor were investigated using tripropylamine as a
representative analyte and low detection limit (SN−1 =3) of 5.0nM was
obtained. It also exhibited more excellent reproducibility (relative standard
deviations of 0.63% for continuous 45 cycles) and long-term stability (∼80% of
its initial ECL intensity could be retained over 3 months). More importantly,
assisted by the developed ECL sensor, discrimination of 1.0nM single-nucleotide
mismatch in human urine matrix could be realized on the PCs for the first
attempt. Thus, the developed sensor was confirmed with the advantages of highly
sensitivity, long-term stability, simplicity, low cost, disposability, high
efficiency and potential applicability.
Graphical abstract
Highlights
► Solid-state ECL sensor
was introduced into paper-based chips for the first time. ► Composite film of
functionalized graphene/Nafion was used for sensor fabrication. ► Excellent
reproducibility and long-term stability were obtained for the sensor. ►
Single-base mismatch detection in human urine was realized on paper-based
chips.
A novel
micro-mixer based on the induced-charge electrokinetic motion of an electrically
conducting particle is proposed and numerically demonstrated in this paper. For
most microfluidic applications, it is desired to mix different streams of
solutions rapidly in a continuous flow mode. Therefore, in this work, we
consider a mixing chamber containing an electrically conducting particle and the
mixing chamber is located in the middle of a microchannel. Vortices are
generated around the electrically conducting particle in an aqueous solution due
to the interaction of the applied electric field and the induced surface charge
on the particle. These vortices will enhance significantly the mixing of
different solutions around the particle. The effectiveness of mixing the two
streams entering the mixing chamber is numerically studied as functions of the
applied electric field. Excellent mixing can be achieved in this system under
two perpendicularly applied electric fields. The proposed micro-mixer is simple
and easy to be fabricated for lab-on-a-chip applications.
Graphical abstract
Highlights
► A novel micro-mixer is
developed based on induced-charge electrokinetic (ICEK). ► Produced vortices
around the electrically conducting particle enhance the mixing. ► Designed
micro-mixer is very efficient and fast. ► This micro-mixer is simple to
fabricate for lab-on-a-chip applications. ► Mixing efficiency is studied as a
function of applied electric field.
Binary
nanoparticles composed of a superparamagnetic Fe3O4 core and an Au nanoshell
(Fe3O4@Au) were prepared via a simple co-precipitation method followed by
seed-mediated growth process. The nanoparticles exhibited functions of both fast
magnetic response and local surface plasmon resonance. The Fe3O4@Au
nanoparticles were used as probes for surface-enhanced Raman scattering (SERS)
using p-thiocresol (p-TC) as reporter molecule. With the ability of analyte
capture and concentration magnetically, the Fe3O4@Au nanoparticles showed
significant SERS properties with excellent reproducibility. Under non-optimized
conditions, detection limit as low as 4.55pM of analyte can be reached using
Fe3O4@Au nanoparticle assemblies, which excel remarkably the cases with
traditional Au nanoprobes.
Graphical abstract
Highlights
► Fe3O4@Au nanoparticle
as substrates for SERS. ► The Fe3O4@Au nanoparticles are modified with analytes
and magnetically separated. ► The non-optimized detection limit is 4.55pM
p-thiocresol ethanol-water solution. ► The detection sensitivity and
reproducibility of SERS is improved.
A novel
homogeneous immunoassay based on Förster resonance energy transfer for sensitive
detection of tumor, e.g., marker with carcinoembryonic antigen (CEA), was
proposed. The assay was consisted of polyclonal goat anti-CEA antibody labeled
luminescent CdTe quantum dots (QDs) as donor and monoclonal goat anti-CEA
antibody labeled gold nanoparticles (AuNPs) as acceptor. In presence of CEA, the
bio-affinity between antigen and antibody made the QDs and AuNPs close enough,
thus the photoluminescence (PL) quenching of CdTe QDs occurred. The PL
properties could be transformed into the fluorometric variation, corresponding
to the target antigen concentration, and could be easily monitored and analyzed
with the home-made image analysis software. The fluorometric results indicated a
linear detection range of 1–110ngmL−1 for CEA, with a detection limit
of 0.3ngmL−1. The proposed assay configuration was attractive for
carcinoma screening or single sample in point-of-care testing, and even field
use. In spite of the limit of available model analyte, this approach could be
easily extended to detection of a wide range of biomarkers.
Graphical abstract
Highlights
A Förster resonance energy transfer system by using
polyclonal goat anti-CEA antibody labeled luminescent CdTe quantum dots (QDs) as
donor and monoclonal goat anti-CEA antibody labeled gold nanoparticles (AuNPs)
as acceptor for sensitive detection of tumor marker was proposed. ► A homogeneous immunosensing strategy based on FRET for
detection of tumor marker was proposed. ► Close of QDs and AuNPs allow the
occurrence of quenching the photoluminescence of nano-bio-probes. ► Signal
quenching was monitored by a self-developed image analyzer. ► The fluorometric
assay format is attractive for widespread carcinoma screening and even field
use.
Diffusive
equilibrium (DET) and diffusive gradient in thin film (DGT) techniques with an
inductively coupled plasma mass spectrometry detection of elements were applied
to characterize uranium, manganese, iron and 238U/235U
isotopic ratio depth profiles in sediment pore water at high spatial resolution
and to monitor uranium uptake/remobilization processes in uranium spiked
sediment core samples under laboratory, well controlled conditions. Modified
constrained sediment DGT probes, packed with Spheron-Oxin® resin gel,
were employed for selective uranium measurements. Spatially resolved DET and DGT
responses were indicative of local redistribution of uranium in naturally
uranium poor and rich sediments.
Graphical abstract
Highlights
. ► Probe for U
detection by diffusive gradient in thin films technique is presented. ►
Selective and spatially resolved depth profiles of U in sediments are monitored.
► U isotopic ratio profiles in DGT and DET measurements are obtained by ICP
MS.
The principal
objective of this work was to develop and demonstrate a new methodology for
silver nanoparticle (AgNP) detection and characterization based on
asymmetric-flow field flow fractionation (A4F) coupled on-line to multiple
detectors and using stable isotopes of Ag. This analytical approach opens the
door to address many relevant scientific challenges concerning the transport and
fate of nanomaterials in natural systems. We show that A4F must be optimized in
order to effectively fractionate AgNPs and larger colloidal Ag particles. With
the optimized method one can accurately determine the size, stability and
optical properties of AgNPs and their agglomerates under variable conditions. In
this investigation, we couple A4F to optical absorbance (UV–vis spectrometer)
and scattering detectors (static and dynamic) and to an inductively coupled
plasma mass spectrometer. With this combination of detection modes it is
possible to determine the mass isotopic signature of AgNPs as a function of
their size and optical properties, providing specificity necessary for tracing
and differentiating labeled AgNPs from their naturally occurring or
anthropogenic analogs. The methodology was then applied to standard estuarine
sediment by doping the suspension with a known quantity of isotopically enriched
109AgNPs stabilized by natural organic matter (standard humic and
fulvic acids). The mass signature of the isotopically enriched AgNPs was
recorded as a function of the measured particle size. We observed that AgNPs
interact with different particulate components of the sediment, and also
self-associate to form agglomerates in this model estuarine system. This work
should have substantial ramifications for research concerning the environmental
and biological fate of AgNPs.
Graphical abstract
Highlights
► Isotopically modified
and unmodified AgNPs characterization by A4F-DAD-MALS–DLS-ICP-MS. ►
Size-resolved characterization and speciation in simple or complex media. ►
Capacity to detect stable isotope enriched AgNPs in a standard estuarine
sediment. ► New opportunities to monitor and study fate and transformations of
AgNPs.
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