46
M. A. Espinosa-Hernandez et al.
the antigen was immobilized on the paper surface of the microfluidic microplate,
reacting with the primary antibody conjugated with alkaline phosphatase (ALP).
The enzymatic reaction between ALP and the colorimetric substrate BCIP/NBT was
what produces the purple color. The colorimetric result could be observed by the
naked eye within an hour or could be alternatively scanned by an office scanner
for quantitative analysis. Figure 2.8e shows the variety of purple shades that corresponded to the concentrations inserted; the highest IgG concentrations resulted in a
darker shade and as that quantity of IgG was decreased, so did the color intensity as
is shown from left to right in the image.
Li et al. (2018) developed a double-layered microfluidic paper-based device
with multiple colorimetric indicators for simultaneous detection of glucose, uric
acid, lactate and choline. Linear calibration curves were obtained to identify these
biomolecules. These values found from the experiments showed great sensibility
(Fig. 2.9a) by exhibiting very wide linear ranges over two to three orders of magnitude: glucose (0.01–10.0 mmol/L), uric acid (0.01–5.0 mmol/L), lactate (0.04–
10.0 mmol/L), and choline (0.04–24.0 mmol/L). The double-layered μPAD was
first designed in AutoCAD. Different patterns were needed as the top layer was
dedicated to detection and the bottom was auxiliary to construct 3D microfluidic
channels. For detection, a 10 mm central sampling zone surrounded by eight 3 ×
8 mm microfluidic channels and eight 6 mm detection zones were created. These
were modified with colorimetric reagents, different kinds of oxidase and HRP, which
Fig. 2.9 a Calibration curves of glucose, uric acid, choline and lactate. b Fabrication of double
layer μPAD Li et al. (2018)
M. A. Espinosa-Hernandez et al.
the antigen was immobilized on the paper surface of the microfluidic microplate,
reacting with the primary antibody conjugated with alkaline phosphatase (ALP).
The enzymatic reaction between ALP and the colorimetric substrate BCIP/NBT was
what produces the purple color. The colorimetric result could be observed by the
naked eye within an hour or could be alternatively scanned by an office scanner
for quantitative analysis. Figure 2.8e shows the variety of purple shades that corresponded to the concentrations inserted; the highest IgG concentrations resulted in a
darker shade and as that quantity of IgG was decreased, so did the color intensity as
is shown from left to right in the image.
Li et al. (2018) developed a double-layered microfluidic paper-based device
with multiple colorimetric indicators for simultaneous detection of glucose, uric
acid, lactate and choline. Linear calibration curves were obtained to identify these
biomolecules. These values found from the experiments showed great sensibility
(Fig. 2.9a) by exhibiting very wide linear ranges over two to three orders of magnitude: glucose (0.01–10.0 mmol/L), uric acid (0.01–5.0 mmol/L), lactate (0.04–
10.0 mmol/L), and choline (0.04–24.0 mmol/L). The double-layered μPAD was
first designed in AutoCAD. Different patterns were needed as the top layer was
dedicated to detection and the bottom was auxiliary to construct 3D microfluidic
channels. For detection, a 10 mm central sampling zone surrounded by eight 3 ×
8 mm microfluidic channels and eight 6 mm detection zones were created. These
were modified with colorimetric reagents, different kinds of oxidase and HRP, which
Fig. 2.9 a Calibration curves of glucose, uric acid, choline and lactate. b Fabrication of double
layer μPAD Li et al. (2018)