60
M. A. Espinosa-Hernandez et al.
polymerase chain reaction (PCR), allowing higher specificity and sensitivity, and
eliminating the bulky thermocycler. A glass microbead-based centrifugal nucleic
acid extraction was used as a solid phase matrix where the genomic DNA could
be purified from the lysate sample. Lastly, the colorimetric based lateral flow strip
provided a cost-effective and equipment-free detection method. The device integrated these three techniques for detecting in a sequential manner with an optimized
microfluidic design and rotational speed control. The microdevice was a five-layer
stacked disc with three identical units. Each unit consisted of three functional parts:
solid phase DNA extraction, LAMP reaction, and a lateral flow strip. The main three
microfluidic layers were created by a CNC milling machine and PSA film was used
once the micropattern was cut by a plotter, following a hot press bonding all layers
together. The first layer had injection holes and microfluidic channels to transport a
LAMP product and a running buffer from the second layer into the lateral flow strip
on the third layer. The second layer contained the micropatterns for DNA extraction and amplification. The third layer was for embedding a lateral flow strip for
the colorimetric detection (Fig. 2.20b). The detection could be made with the naked
eye due to the LAMP product. In order to do so, a lateral flow strip containing
a buffer loading pad for introducing a running buffer, a conjugate pad (including
streptavidin coated AuNPs for the conjugation with the LAMP products), a detection zone (where anti-Digoxigenin, anti-Texas Red and biotin were immobilized in
the test line 1, test line 2, and control line, respectively), and an absorbent pad for
liquid wicking were incorporated within the device. Thermal guards were patterned
around the lateral flow strips to prevent the heat from influencing the anti-haptens
on the detection zone of the lateral flow strips. The resulting microdevice presented
great potentials as a user-friendly POC analyzer for application in resource-limited
setups. The design allowed efficient fluid transfer without sample loss from sample
pretreatment to strip detection. The automatic and integrated genetic analysis could
then be successfully performed by controlling the rotational speed without the use
of expensive equipment.
A cheap and portable smartphone spectrometer for monitoring optical changes
as they occur was created by Wang et al. (2016). The device was aimed at detecting
glucose and troponin I, a myocardial infarction biomarker by means of a smartphone
with a built-in LED and complementary metal oxide semiconductor (CMOS) camera
to use as the light source and the detector, respectively. No external light source,
lens, or filter were required. As the dispersive unit, a CD with grating was used. For
human cardiac troponin I detection, peptide functionalized AuNPs were taken as
the reporters. For the detection of glucose, a solution of 2,2
-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), HRP, and glucose oxidase (GOx) was utilized. A
bi-enzymatic cascade assay was used where the glucose was catalytically converted
into hydrogen peroxide, which then converts ABTS by HRP into oxidized form.
Once oxidized, a blue color appeared and was read from the color band with the
spectrometer bases on the change of intensity. The spectrometer relied on a sample
cell with an integrated grating substrate, and the phone’s LED flash and camera.
The CD was placed 50 mm away from the LED and tilted 5º so that the flashlight
passed through a 1 mm diameter pinhole. The grating tracks were aligned to the
M. A. Espinosa-Hernandez et al.
polymerase chain reaction (PCR), allowing higher specificity and sensitivity, and
eliminating the bulky thermocycler. A glass microbead-based centrifugal nucleic
acid extraction was used as a solid phase matrix where the genomic DNA could
be purified from the lysate sample. Lastly, the colorimetric based lateral flow strip
provided a cost-effective and equipment-free detection method. The device integrated these three techniques for detecting in a sequential manner with an optimized
microfluidic design and rotational speed control. The microdevice was a five-layer
stacked disc with three identical units. Each unit consisted of three functional parts:
solid phase DNA extraction, LAMP reaction, and a lateral flow strip. The main three
microfluidic layers were created by a CNC milling machine and PSA film was used
once the micropattern was cut by a plotter, following a hot press bonding all layers
together. The first layer had injection holes and microfluidic channels to transport a
LAMP product and a running buffer from the second layer into the lateral flow strip
on the third layer. The second layer contained the micropatterns for DNA extraction and amplification. The third layer was for embedding a lateral flow strip for
the colorimetric detection (Fig. 2.20b). The detection could be made with the naked
eye due to the LAMP product. In order to do so, a lateral flow strip containing
a buffer loading pad for introducing a running buffer, a conjugate pad (including
streptavidin coated AuNPs for the conjugation with the LAMP products), a detection zone (where anti-Digoxigenin, anti-Texas Red and biotin were immobilized in
the test line 1, test line 2, and control line, respectively), and an absorbent pad for
liquid wicking were incorporated within the device. Thermal guards were patterned
around the lateral flow strips to prevent the heat from influencing the anti-haptens
on the detection zone of the lateral flow strips. The resulting microdevice presented
great potentials as a user-friendly POC analyzer for application in resource-limited
setups. The design allowed efficient fluid transfer without sample loss from sample
pretreatment to strip detection. The automatic and integrated genetic analysis could
then be successfully performed by controlling the rotational speed without the use
of expensive equipment.
A cheap and portable smartphone spectrometer for monitoring optical changes
as they occur was created by Wang et al. (2016). The device was aimed at detecting
glucose and troponin I, a myocardial infarction biomarker by means of a smartphone
with a built-in LED and complementary metal oxide semiconductor (CMOS) camera
to use as the light source and the detector, respectively. No external light source,
lens, or filter were required. As the dispersive unit, a CD with grating was used. For
human cardiac troponin I detection, peptide functionalized AuNPs were taken as
the reporters. For the detection of glucose, a solution of 2,2
-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), HRP, and glucose oxidase (GOx) was utilized. A
bi-enzymatic cascade assay was used where the glucose was catalytically converted
into hydrogen peroxide, which then converts ABTS by HRP into oxidized form.
Once oxidized, a blue color appeared and was read from the color band with the
spectrometer bases on the change of intensity. The spectrometer relied on a sample
cell with an integrated grating substrate, and the phone’s LED flash and camera.
The CD was placed 50 mm away from the LED and tilted 5º so that the flashlight
passed through a 1 mm diameter pinhole. The grating tracks were aligned to the