3 Aptamer-Based Point of Care Testing Schemes
65
meter app. The designed device ensured excellent selectivity and sensitivity in a
mixture of other interfering heavy metal ions with an LOD of 0.28 ng.mL
−1 in the
dynamic range of 1–32 ng.mL
−1 [70].
Abdelli et al. presented aptamer-based allergen sensing system. They inserted
aptamer sheet of PDMS on the glass plate on the tip of the device. The sample was
applied to the aptamer film. Once the tip of the device is closed with the cover,
the illumination system starts automatically. The device sends the excitation light
toward the aptamer film and receives the emission light captured by the camera in
case any allergens are present in the sample. After capturing the film image, the device
performs the image processing and the results are interpreted, recorded, displayed
and wirelessly sent to the smartphone [71].
Cheng and colleagues developed a fluorescent aptamer-based lateral flow
biosensor (apta-LFB) combined with fluorophore-quencher nanopairs and a Smartphone’s reader to achieve triple-target detection of pesticides: chlorpyrifos, diazinon,
and malathion. Aptamers served as recognition elements in LFB, offering better
specificity and stability. A novel fluorophore-quencher nanopair (quantum dots
nanobeads and gold nanostars) was implemented to perform “signal-on” instead
of “signal-off.” After optimization, LOD for chlorpyrifos, diazinon, and malathion
was determined to be 0.73 ng.mL
−1 , 6.7 ng.mL
−1 , and 0.74 ng.mL
−1 , respectively.
The highly increased sensitivity was due to the combination of improved signal and
minimal background [72].
Li et al. developed a cost-effective latent tuberculosis infection (LTBI) screening
system-based on enzyme-linked aptamers using a smartphone. Specific recognition
of mannose-capped lipo-arabino-mannan on the surface of Mycobacterium tuberculosis was achieved for the development of direct and indirect dot-blot approaches,
which were designed for quantitative analysis of multiple samples and identification
of mycobacterial strains. Compared with traditional acid-fast staining assay used for
LTBI screening, the direct dot-blot system delivered a lower LOQ at 104 CFUmL
−1
and higher accuracy [73].
3.3.6 Microchannels/Microfluidics
One of the ways to control the flow of fluids at microlevels is to design the devices
with microchannels. Microchannels are needed when samples amount are small or
samples need to be used with precautions to prevent disease spread. Specific fluid
samples such as blood that involve unknown pathogens, requiring careful handling
of these samples. Microchannels help in sample movement, mixing, separating and
other procedures [74].
Weng and Neethirajan developed a microfluidic system integrated with a quantum
dots (Qdots) aptamer functionalized graphene oxide (GO) nanobiosensor for simple,
rapid, and sensitive allergen detection for foodborne diseases. The biosensor used
Qdots-aptamer-GO complexes as probes to undergo conformational change upon
65
meter app. The designed device ensured excellent selectivity and sensitivity in a
mixture of other interfering heavy metal ions with an LOD of 0.28 ng.mL
−1 in the
dynamic range of 1–32 ng.mL
−1 [70].
Abdelli et al. presented aptamer-based allergen sensing system. They inserted
aptamer sheet of PDMS on the glass plate on the tip of the device. The sample was
applied to the aptamer film. Once the tip of the device is closed with the cover,
the illumination system starts automatically. The device sends the excitation light
toward the aptamer film and receives the emission light captured by the camera in
case any allergens are present in the sample. After capturing the film image, the device
performs the image processing and the results are interpreted, recorded, displayed
and wirelessly sent to the smartphone [71].
Cheng and colleagues developed a fluorescent aptamer-based lateral flow
biosensor (apta-LFB) combined with fluorophore-quencher nanopairs and a Smartphone’s reader to achieve triple-target detection of pesticides: chlorpyrifos, diazinon,
and malathion. Aptamers served as recognition elements in LFB, offering better
specificity and stability. A novel fluorophore-quencher nanopair (quantum dots
nanobeads and gold nanostars) was implemented to perform “signal-on” instead
of “signal-off.” After optimization, LOD for chlorpyrifos, diazinon, and malathion
was determined to be 0.73 ng.mL
−1 , 6.7 ng.mL
−1 , and 0.74 ng.mL
−1 , respectively.
The highly increased sensitivity was due to the combination of improved signal and
minimal background [72].
Li et al. developed a cost-effective latent tuberculosis infection (LTBI) screening
system-based on enzyme-linked aptamers using a smartphone. Specific recognition
of mannose-capped lipo-arabino-mannan on the surface of Mycobacterium tuberculosis was achieved for the development of direct and indirect dot-blot approaches,
which were designed for quantitative analysis of multiple samples and identification
of mycobacterial strains. Compared with traditional acid-fast staining assay used for
LTBI screening, the direct dot-blot system delivered a lower LOQ at 104 CFUmL
−1
and higher accuracy [73].
3.3.6 Microchannels/Microfluidics
One of the ways to control the flow of fluids at microlevels is to design the devices
with microchannels. Microchannels are needed when samples amount are small or
samples need to be used with precautions to prevent disease spread. Specific fluid
samples such as blood that involve unknown pathogens, requiring careful handling
of these samples. Microchannels help in sample movement, mixing, separating and
other procedures [74].
Weng and Neethirajan developed a microfluidic system integrated with a quantum
dots (Qdots) aptamer functionalized graphene oxide (GO) nanobiosensor for simple,
rapid, and sensitive allergen detection for foodborne diseases. The biosensor used
Qdots-aptamer-GO complexes as probes to undergo conformational change upon