16 research outputs found
Classification of three pure bacteria after wash
No full textClassification of three pure bacteria after was
Classification of three bacteria from LB medium
No full textClassification of three bacteria from LB mediu
SERS Detection of Bacteria in Water by in Situ Coating with Ag Nanoparticles
No full textThe bio-sensing for the convenient
detection of bacteria has been
widely explored with the use of various sensing materials and techniques.
It is still a challenge to achieve an ultrasensitive and selective,
but simple, rapid, and inexpensive detection method for bacteria.
We report on surface-enhanced Raman scattering (SERS) for the detection
of living bacteria in drinking water by employing a synthesis of silver
nanoparticles coating the cell wall of bacteria. We found that the
Raman signals intensity of bacteria after AgNP synthesis mainly depends
on the zeta potential of the cell wall. The enhancement of the Raman
signal of bacteria using this strategy is about 30-fold higher than
that in the case of a simply mixed colloid–bacterial suspension.
The total assay time required is only 10 min and the total reactants’
volume needed to analyze bacteria in a real environment is as low
as 1 mL. Particularly, only one droplet of 3 μL sample is necessary
for each SERS measurement. Furthermore, we can use this novel strategy
to discriminate three strains of Escherichia coli and one strain of Staphylococcus epidermidis by hierarchy cluster analysis. Finally, we can detect bacteria down
to 2.5 × 10<sup>2</sup> cells/mL on a hydrophobic glass slide
by SERS mapping. Thus, our detection method offers prominent advantages,
such as reduced assay time, simple handling, low reactant volumes,
small amount of sample, and higher sensitivity and selectivity compared
to previously reported label free methods. This novel strategy may
be extended to open an avenue for developing various SERS-based biosensors
Label-Free in Situ Discrimination of Live and Dead Bacteria by Surface-Enhanced Raman Scattering
No full textTechniques to distinguish between
live and dead bacteria in a quantitative
manner are in high demand in numerous fields including medical care,
food safety, and public security as well as basic science research.
This work demonstrates new nanostructures (silver nanoparticles coating
bacteria structure, Bacteria@AgNPs) and their utility for rapid counting
of live and dead bacteria by surface-enhanced Raman scattering (SERS).
We found that suspensions containing Gram-negative organisms as well
as AgNPs give strong SERS signals of live bacteria when generated
selectively on the particle surface. However, almost no SERS signals
can be detected from Bacteria@AgNPs suspensions containing dead bacteria.
We demonstrate successful quantification of different percentages
of dead bacteria both in bulk liquid and on glass surfaces by using
SERS mapping on a single cell basis. Furthermore, different chemicals
have been used to elucidate the mechanism involved in this observation.
Finally, we used the Bacteria@AgNPs method to detect antibiotic resistance
of <i>E. coli</i> strains against several antibiotics used
in human medicine
Microfluidic Actuation via 3D-Printed Molds toward Multiplex Biosensing of Cell Apoptosis
No full textMultiplexed analysis of biochemical
analytes such as proteins,
enzymes, and immune products using a microfluidic device has the potential
to cut assay time, reduce sample volume, realize high-throughput,
and decrease experimental error without compromising sensitivity.
Despite these huge benefits, the need for expensive specialized equipment
and the complex photolithography fabrication process for the multiplexed
devices have, to date, prevented widespread adoption of microfluidic
systems. Here, we present a simple method to fabricate a new microfluidic-based
multiplexed biosensing device by taking advantage of 3D-printing.
The device is an integration of normally closed (NC) microfluidic
valving units which offer superior operational flexibility by using
PDMS membrane (E ∼ 1–2 MPa) and require
minimized energy input (1–5 kPa). To systematically engineer
the device, we first report on the geometrical and operational analysis
of a single 3D-printed valving unit. Based on the characterization,
we introduce a full prototype multiplexed chip comprising several
microfluidic valves. The prototype offersfor the first time
in a 3D-printed microfluidic devicethe capability of on-demand
performce of both a sequential and a parallel biochemical assay. As
a proof of concept, our device has been used to simultaneously measure
the apoptotic activity of 5 different members of the caspase protease
enzyme family. In summary, the 3D-printed valving system showcased
in this study overcomes traditional bottlenecks of microfabrication,
enabling a new class of sophisticated liquid manipulation required
in performing multiplexed sensing for biochemical assays
Development of Recombinase-Aided Amplification (RAA)-Exo-Probe and RAA-CRISPR/Cas12a Assays for Rapid Detection of Campylobacter jejuni in Food Samples
No full textCampylobacter jejuni is
the major
cause of campylobacteriosis, one of the most common foodborne illnesses
worldwide. Here, we report the development of RAA-exo-probe and RAA-CRIPSR/Cas12a
assays for the detection of C. jejuni in food samples. The two assays were found to be highly specific
to C. jejuni and highly sensitive,
as they were one log more sensitive compared to the traditional culture
method, with detection thresholds of 9 and 5 copies per reaction,
respectively. These assays successfully detected C.
jejuni in spiked chicken samples and natural meat
samples (chicken, beef, mutton, etc.) and were overall less dependent
on expensive equipment, only requiring a fluorescent reader. Their
ease of use compared to other nucleic acid amplification-based methods
indicates that these assays could be adapted for the rapid, routine
surveillance of C. jejuni contamination
in food samples, particularly for work done in the field or poorly
equipped labs
