140
A. S. Cerda-Kipper and S. Hosseini
sites. Expectedly, a higher concentration of OTA will decrease the anti-OTA antibodies available to bind OTA-BSA molecules, hence a decrease of the icELISA.
For readout, an optical microscope was used for the detection of CL light emission.
The results indicated that the icELISA is a flexible and adaptable method that, when
coupled with suitable sample extraction strategies, can be used for detecting OTA
in complex matrices. Through this configuration, the authors successfully decreased
measurement errors leading to an improvement of one order of magnitude in the
LOD. The proposed platform in this study can be further developed into a future
highly sensitive, portable, and fully integrated “toxin-chip” for monitoring food
safety (Novo et al. 2013).
Ramon et al. (2017) developed a proof-of-concept of CL generation and detection in a capillary-driven microfluidic chip for potential immunoassay applications,
as suggested in Table 6.1. Instead of using a complex assay protocol, the authors
explored the CL generation under flow conditions using a simplified immunoassay
model using an acridan-based reaction, catalyzed by HRP. A PDMS sealing layer
was fabricated using stencil deposition and the CL substrate was flowing through the
hydrophilic channels inside the PDMS device. The fabrication of the microfluidic
chips involved dry etching of Si wafers using a deep reaction ion etching (DRIE)
tool. Single side polished silicon wafers were used as the main substrate. After
priming the wafer surface with HMDS vapor, a positive-tone photoresist was coated
using a spin coater. By using a laser writing tool, the photoresist added nomenclature into the structure. This approach was more convenient for rapid fabrication of
several design iterations compared to writing masks. Following the development
of the exposed resist, the Si substrate was etched. The photoresist mask was then
removed using a strong oxygen plasma etching for 5 min. The wafer was diced, and
the chips were separated using the “chip-olate” process. Each chip comprised of
loading pad surrounded with anti-wetting structures to avoid undesired spreading of
a liquid placed on the pad, a detection area, where the HRP molecules were localized,
and two capillary pumps that were connected in series. An air vent was connected to
the last capillary pump to avoid air from escaping the flow path. Four independent
channels were connected to the same loading pad and run through the detection area.
Finally, the chips were sealed with the HRP coated PDMS and with a blank PDMS
with integrated microbeads. By using capillary forces and evaporation-driven flow,
the CL substrate was led through the device and produced the emission after coming
into contact with HRP. The HRP was either coated inside the device or on the surface
of the microbeads. The CL signal was recorded by an optical detector. This device
has granted a better understanding of flow conditions and integrated several different
strategies in a single platform (Ramon et al. 2017).
Novo et al. presented a hand-held, user-friendly POC platform, which was an
incorporation of an autonomous capillary microfluidic based CL ELISA. The microfabrication of the device was performed through the use of transducers (a-Si:H photodiodes) as well as electronics implemented for data acquisition, with an integrated
portable optical detection box, consisting of a microfabricated photodiode chip on
glass attached to a printed circuit board (PCB) and a microcontroller (Table 6.1).
A. S. Cerda-Kipper and S. Hosseini
sites. Expectedly, a higher concentration of OTA will decrease the anti-OTA antibodies available to bind OTA-BSA molecules, hence a decrease of the icELISA.
For readout, an optical microscope was used for the detection of CL light emission.
The results indicated that the icELISA is a flexible and adaptable method that, when
coupled with suitable sample extraction strategies, can be used for detecting OTA
in complex matrices. Through this configuration, the authors successfully decreased
measurement errors leading to an improvement of one order of magnitude in the
LOD. The proposed platform in this study can be further developed into a future
highly sensitive, portable, and fully integrated “toxin-chip” for monitoring food
safety (Novo et al. 2013).
Ramon et al. (2017) developed a proof-of-concept of CL generation and detection in a capillary-driven microfluidic chip for potential immunoassay applications,
as suggested in Table 6.1. Instead of using a complex assay protocol, the authors
explored the CL generation under flow conditions using a simplified immunoassay
model using an acridan-based reaction, catalyzed by HRP. A PDMS sealing layer
was fabricated using stencil deposition and the CL substrate was flowing through the
hydrophilic channels inside the PDMS device. The fabrication of the microfluidic
chips involved dry etching of Si wafers using a deep reaction ion etching (DRIE)
tool. Single side polished silicon wafers were used as the main substrate. After
priming the wafer surface with HMDS vapor, a positive-tone photoresist was coated
using a spin coater. By using a laser writing tool, the photoresist added nomenclature into the structure. This approach was more convenient for rapid fabrication of
several design iterations compared to writing masks. Following the development
of the exposed resist, the Si substrate was etched. The photoresist mask was then
removed using a strong oxygen plasma etching for 5 min. The wafer was diced, and
the chips were separated using the “chip-olate” process. Each chip comprised of
loading pad surrounded with anti-wetting structures to avoid undesired spreading of
a liquid placed on the pad, a detection area, where the HRP molecules were localized,
and two capillary pumps that were connected in series. An air vent was connected to
the last capillary pump to avoid air from escaping the flow path. Four independent
channels were connected to the same loading pad and run through the detection area.
Finally, the chips were sealed with the HRP coated PDMS and with a blank PDMS
with integrated microbeads. By using capillary forces and evaporation-driven flow,
the CL substrate was led through the device and produced the emission after coming
into contact with HRP. The HRP was either coated inside the device or on the surface
of the microbeads. The CL signal was recorded by an optical detector. This device
has granted a better understanding of flow conditions and integrated several different
strategies in a single platform (Ramon et al. 2017).
Novo et al. presented a hand-held, user-friendly POC platform, which was an
incorporation of an autonomous capillary microfluidic based CL ELISA. The microfabrication of the device was performed through the use of transducers (a-Si:H photodiodes) as well as electronics implemented for data acquisition, with an integrated
portable optical detection box, consisting of a microfabricated photodiode chip on
glass attached to a printed circuit board (PCB) and a microcontroller (Table 6.1).