DNA SORTERS-A Review
ONCHIP DETECTION OF DNA USING GOLD NANORINGS
INTEGRATED MICROFLUDIC BASED ELECTOCHEMICAL DNA SENSOR
DNA sorter refers to detection of DNA in a bio fluid (Blood)
Separation of specific DNA strand from a fluid
GOLD NANORING AS A SENSITIVE PLASMONIC BIOSENSOR FOR ON-CHIP
DETECTIONLocalized Surface Plasmon Resonance (LSPR)
LSPR are unique and sensitive to RI change.
Previous methods using various nanostructures such as
nanodiscs,nanorods,nanospheres and Nano holes.
In this paper , the authors investigated the LSPR based DNA
detector to detect target DNA Sequence.
They probe immobilize the ssDNA on the sensor and detect the
FABRICATION OF GOLD NANORINGS
The gold nanorings were fabricated using nanosphere
The substrate used was Quartz
Typical size of the nanorings are 50nm and the space between the
nanorings are 200nm
CHARACTERIZATION OF NANORINGS
WORKING PRINCIPLE OF THE BIO SENSOR
The bio sensor measures the change in Refractive index due to
the introduction of external biomolecules.
The sensitivity of the biochip is explored by injecting various
glycerol/water mixture on the biochip and corresponding LSPR
spectra were analyzed.
LSPR PROFILE OF VARIOUS MIXTURES OF GLYCEROL/WATER
Linear regression analysis of LSPR spectra indicates the RI
sensitivity of 350 nm/RIU . (Previous results were around
When compared to a similar chip fabricated by E-Beam
Lithography, which has RI sensitivity around 333nm/RIU.
FoM values nearly 3.1,(FoM=RI Sensitivity/FWHM)
Higher value than previous values which indicates high
capability of the sensor.
ANALYSIS OFDNA SENSIBILITY
METHODOLOGYTo demonstrate the DNA detection, the LSPR spectra
were monitored upon
the ssDNA probe immobilization on the nanosensor surface and the
subsequent hybridization with complementary target DNA.
A 25-nucleotides long thiolated ssDNA probes (MW: 8 kDa)
dissolved in an immobilization buffer were injected into for 45 min
with a flow rate of 20 l/min. After ssDNA probe immobilization on
the Nano sensor via a thiol-gold bond, the sensor surface was
rinsed with 1mM 11-mercapto-1-undercanol for 15 min to eliminate
the possible non-specific DNA adherence on the nanosensor.
Complementary DNA hybridization was performed by injecting 100nM
complementary DNA (25-nucleotides long) in a hybridization buffer
into the sensor-chip for 45 min.
ANALYSIS OF DNA SENSING RESULTSAfter the ssDNA probe
the LSPR peak position red-shifted 8.2 nm . More interestingly,
after the hybridization with the complementary target DNA, the LSPR
peak position further red-shifted 3.1 nm.
In contrast, a non complementary target DNA injection for the
same time only caused 0.19 nm shift, indicating a good specificity
of the nanosensor. In this research, the DNA probe immobilization
and the hybridization procedures were both performed for 45 min
CONCLUSION OF PAPER
Nanoparticles based sensors tends to aggregate and forms loosens
from the substrates. (Because of exposure of ionic buffer
Nanoring structure shows good stability in the exposure of ionic
Thin layer of Ti was deposited for improve the adhesion
The results was discussed in the paper with measurement of LSPR
spectra of the sensor with different concentration of ionic
solution concentration and various flow rate.
INTEGRATED MICROFLUIDIC ELECTROCHEMICAL DNA
SENSORThe Integrated Microfluidic Electrochemical DNA (IMED)
combines three key biochemical functionalities symmetric PCR,
enzymatic single-stranded DNA generation, and sequence-specific
electrochemical detections in a disposable, monolithic chip.
Device size:73 X 13mm Six Fluidics inlet/outlets Detection
electrodes of area19mm2
DNA of Interest
PCR with a primer
Exonucleotide based digestion
OVERVIEW OF PAPER
As a model the authors attempted to detect Gry B gene of
Salmonella enterica serovar Typhimurium
They demonstrated detection of specific gene of concentration as
low as 10aM. (Atto molar)
(A) Template DNA is added to a PCR The
template is PCR amplified. (C)
(D) Lambda exonuclease is mixed.
(E) MgCl2 is added to the IMED chip to adjust the
from 1.5 mM to 50 mM to optimize the
(F) a baseline redox current is measured via ACV.
The ssDNA product hybridizes with the E-DNA
probe modulating the redox current signal.
Finally, the E-DNA probe is regenerated to verify
the hybridization event.
DEMONSTRATION OF ON-CHIP PCR AND SSDNA GENERATION.
Lane 1, 100 base-pair ladder;
lane 2, positive control from bench top thermal cycler;
lane 3, negative control from the IMED chip without template
lane 4, IMED output with template DNA, which showed similar
efficiency to the bench top thermal cycler; and
lane 5, IMED output after ssDNA generation. The lower band is
ssDNA and upper band indicates incompletely digested
CHANGE IN FARADAIC CURRENT
The no-template negative control yielded 96% of the
baseline (green). Signals in panels B and C were
also compared against externally prepared zero-template
controls, which resulted in drops of 1% and 0%, respectively
EDNA SENSOR RESPONSE
E-DNA sensor response as a function of
The E-DNA sensor signal, as represented
by the percent change in
peak current between the baseline and
after incubation with synthetic
DNA target for 30 min. The standard
deviation for each point was
calculated from three measurements from
three separate chips.
The integrated Microfluidic Electrochemical sensor of system
represents a completely integrated electrochemical DNA detection
architecture with a limit of detection of
REFERENCE PAPER 1
Gold nanoring as a sensitive plasmonic biosensor for on-chip DNA
Authors: Chengjun Huang, Jian Ye, Shuo Wang, Tim Stakenborg, and
Journal: Appl. Phys. Lett. 100, 173114 (2012); doi:
REFERENCE PAPER 2
Integrated Microfluidic Electrochemical DNA Sensor
Brian S. Ferguson, Steven F. Buchsbaum, James S. Swensen,,
KuangwenHsieh, Xinhui Lou,and H. Tom Soh*,,
Department of Mechanical Engineering, University of California,
Santa Barbara, California 93106, College of Creative Studies,
Physics, University of California, Santa Barbara, California 93106,
and Department of Materials, University of California, Santa
Barbara, California 93106
Journal:Anal. Chem. 2009, 81, 65036508