4 research outputs found
Electrochemical Detection of Peanut Allergen Ara h 1 Using a Sensitive DNA Biosensor Based on Stem–Loop Probe
A novel electrochemical DNA sensor was developed by using
a stem–loop
probe for peanut allergen Ara h 1 detection. The probe was modified
with a thiol at its 5′ end and a biotin at its 3′ end.
The biotin-tagged “molecular beacon”-like probe was
attached to the surface of a gold electrode to form a stem–loop
structure by self-assembly through facile gold–thiol affinity.
6-Mercaptohexanol (MCH) was used to cover the remnant bare region.
The stem–-loop probe was “closed” when the target
was absent, and then the hybridization of the target induced the conformational
change to “open”, along with the biotin at its 3′
end moved away from the electrode surface. The probe conformational
change process was verified by circular dichroism (CD); meanwhile,
electron-transfer efficiency changes between probe and electrode were
proved by electrochemical impedance spectroscopy (EIS). The detection
limit of this method was 0.35 fM with the linear response ranging
from 10<sup>–15</sup> to 10<sup>–10</sup> M. Moreover,
a complementary target could be discriminated from one-base mismatch
and noncomplementarity. The proposed strategy has been successfully
applied to detect Ara h 1 in the peanut DNA extracts of peanut milk
beverage, and the concentration of it was 3.2 × 10<sup>–13</sup> mol/L
Development and Application of 3‑Chloro-1,2-propandiol Electrochemical Sensor Based on a Polyaminothiophenol Modified Molecularly Imprinted Film
In this work, a novel electrochemical
sensor for 3-chloro-1,2-propandiol
(3-MCPD) detection based on a gold nanoparticle-modified glassy carbon
electrode (AuNP/GCE) coated with a molecular imprinted polymer (MIP)
film was constructed. <i>p</i>-Aminothiophenol (<i>p</i>-ATP) and 3-MCPD were self-assembled on a AuNP/GCE surface,
and then a MIP film was formed by electropolymerization. The 3-MCPD
template combined with <i>p</i>-ATP during self-assembly
and electropolymerization, and the cavities matching 3-MCPD remained
after the removal of the template. The MIP sensor was characterized
by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and
scanning electron microscopy (SEM). Many factors that affected the
performance of the MIP membrane were discussed and optimized. Under
optimal conditions, the DPV current was linear with the log of the
3-MCPD concentration in the range from 1.0 × 10<sup>–17</sup> to 1.0 × 10<sup>–13</sup> mol L<sup>–1</sup> (<i>R</i><sup>2</sup> = 0.9939), and the detection limit was 3.8
× 10<sup>–18</sup> mol L<sup>–1</sup> (S/<i>N</i> = 3). The average recovery rate of 3-MCPD from spiked
soy sauce samples ranged from 95.0% to 106.4% (RSD < 3.49%). Practically,
the sensor showed high sensitivity, good selectivity, excellent reproducibility,
and stability during the quantitative determination of 3-MCPD
Cell Based-Green Fluorescent Biosensor Using Cytotoxic Pathway for Bacterial Lipopolysaccharide Recognition
Lipopolysaccharide (LPS), a characteristic
component of the outer
membrane of Gram-negative bacteria, can be used as an effective biomarker
to detect bacterial contamination. Here, we reported a 293/hTLR4A-MD2-CD14
cell-based fluorescent biosensor to detect and identify LPS, which
is carried out in a 96-well microplate which is nondestructive, user-friendly,
and highly efficient. The promoter sequence of the critical signaling
pathway gene <i>ZC3H12A</i> (encoding MCPIP1 protein) and
enhanced green fluorescence protein (EGFP) were combined to construct
a recombinant plasmid, which was transferred into 293/hTLR4A-MD2-CD14
cells through lipid-mediated, DNA-transfection way. LPS was able to
bind to TLR4 and coreceptors-induced signaling pathway could result
in green fluorescent protein expression. Results show that stable
transfected 293/hTLR4A-MD2-CD14 cells with LPS treatment could be
directly and continually observed under a high content screening imaging
system. The novel cell-based biosensor detects LPS at low concentration,
along with the detection limit of 0.075 ÎĽg/mL. The cell-based
biosensor was evaluated by differentiating Gram-negative and Gram-positive
bacteria and detecting LPS in fruit juices as well. This proposed
fluorescent biosensor has potential in sensing LPS optically in foodstuff
and biological products, as well as bacteria identification, contributing
to the control of foodborne diseases and ensurance of public food
safety with its high throughput detection way
Ultrasensitive “FRET-SEF” Probe for Sensing and Imaging MicroRNAs in Living Cells Based on Gold Nanoconjugates
MicroRNAs
(miRNAs), a kind of single-stranded small RNA molecule,
play significant roles in the physiological and pathological processes
of human beings. Currently, miRNAs have been demonstrated as important
biomarkers critically related to many diseases and life nature, including
several cancers and cell senescence. It is valuable to establish sensitive
assays for monitoring the levels of intracellular up-regulated/down-regulated
miRNA expression, which would contribute to the early prediction of
the tumor risk and cardiovascular disease. Here, an oriented gold
nanocross (AuNC)-decorated gold nanorod (AuNR) probe with “OFF-enhanced
ON” fluorescence switching was developed based on fluorescence
resonance energy transfer and surface enhanced fluorescence (FRET-SEF)
principle. The nanoprobe was used to specifically detect miRNA in
vitro, which gave two linear responses represented by the equation <i>F</i> = 1830.32 log <i>C</i> + 6349.27, <i>R</i><sup>2</sup> = 0.9901, and <i>F</i> = 244.41 log <i>C</i> + 1916.10, <i>R</i><sup>2</sup> = 0.9984, respectively,
along with a detection limit of 0.5 aM and 0.03 fM, respectively.
Furthermore, our nanoprobe was used to dynamically monitor the expression
of intracellular up-regulated miRNA-34a from the HepG2 and H9C2 cells
stimulated by AFB1 and TGF-β1, and the experimental results
showed that the new probe not only could be used to quantitively evaluate
miRNA oncogene in vitro, but also enabled tracking and imaging of
miRNAs in living cells