3 Bio-microelectromechanical Systems (BioMEMS) in Bio-sensing …
85
geometry was created on the paper by wax printing. A half of the device was dedicated to the detection of metallic ions including Hg
2+ and Ag
+ via functionalization
with ss-DNA strand that quenches the fluorescence of deposited Cy5 marker. Upon
contact with the metallic ions, Hg
2+ and Ag
+ reacted with the thymine and cytosine
bases respectively, which freed the Cy5 marker and allowed a fluorescent response
to be read out. The second half of the device was devoted to the sensing of antibiotic residues. The method of detection in this other half was almost opposite as
shown in Fig. 3.2. The interaction between the antibiotic residue and the graphene
oxide surface, with the fluorescent probe, resulted in fluorescent quenching. Thus,
the detection of this third analyte was measured by a decrease in the fluorescence
signal. The device has shown a high level of specificity for the detection of the metal
ions. However, it showed cross-compatibility between aminoglycoside antibiotics
due to the similarly arranged amino groups that could react with the epoxy groups
of the graphene oxide surface as well hence resulting in less reliable outcomes.
3.4 Microfluidic BioMEMS Recent Advances
of Fluorescence Detection in Microfluidic BioMEMS
3.4.1 Recent Advances of Fluorescence Detection
in Lab-On-Chip (LOC) Devices
Through the combination of biological assays such as ELISA with microfluidic
technologies, it is possible to design biosensors that operate on minimal sample
volumes and offer accurate detection outcomes, while being portable, and often
reusable (Acharya et al. 2015; Fan et al. 2013; Knob et al. 2018; Montón et al.
2017; Onishi 2017). In this chapter some of the latest examples of the microfluidic
BioMEMS for fluorescent detection are as provided.
The organic electroluminescent diode (OLED) has been studied as an economic
and easy to manufacture source of light (energy). It is an attractive option not only for
the possibility of reducing production costs, but also for the high degree of specificity
it offers with respect to the light wavelength it emits. A device that integrates OLED
in a microfluidic device was reported by Acharya et al. (2015). The proposed LOC
(Fig. 3.3) used an AlQ3 OLED to activate fluorescent dye Alexafluor 488 as part of
a fluorescent assay for bio-optical detection of the antigens. The target antigen was
anti-sheep IgGs, which were fluorescently tagged and were detected via a sandwich
immunoassay after conjugating with monoclonal antibodies (Fig. 3.4). A common
issue when designing such devices is the interference of the light source with the
fluorescence as it may result in bleaching. To avoid such problem, a filter can be
used to allow only certain wavelength of the emitted light to reach the sample and
sensor. The excitation peak of the fluorophore should then be lower than the emission
peak, thus allowing the tag’s fluorescence to accurately reflect the presence of the
antigen. Another concern regarding the OLED source is the inevitable heating of the
85
geometry was created on the paper by wax printing. A half of the device was dedicated to the detection of metallic ions including Hg
2+ and Ag
+ via functionalization
with ss-DNA strand that quenches the fluorescence of deposited Cy5 marker. Upon
contact with the metallic ions, Hg
2+ and Ag
+ reacted with the thymine and cytosine
bases respectively, which freed the Cy5 marker and allowed a fluorescent response
to be read out. The second half of the device was devoted to the sensing of antibiotic residues. The method of detection in this other half was almost opposite as
shown in Fig. 3.2. The interaction between the antibiotic residue and the graphene
oxide surface, with the fluorescent probe, resulted in fluorescent quenching. Thus,
the detection of this third analyte was measured by a decrease in the fluorescence
signal. The device has shown a high level of specificity for the detection of the metal
ions. However, it showed cross-compatibility between aminoglycoside antibiotics
due to the similarly arranged amino groups that could react with the epoxy groups
of the graphene oxide surface as well hence resulting in less reliable outcomes.
3.4 Microfluidic BioMEMS Recent Advances
of Fluorescence Detection in Microfluidic BioMEMS
3.4.1 Recent Advances of Fluorescence Detection
in Lab-On-Chip (LOC) Devices
Through the combination of biological assays such as ELISA with microfluidic
technologies, it is possible to design biosensors that operate on minimal sample
volumes and offer accurate detection outcomes, while being portable, and often
reusable (Acharya et al. 2015; Fan et al. 2013; Knob et al. 2018; Montón et al.
2017; Onishi 2017). In this chapter some of the latest examples of the microfluidic
BioMEMS for fluorescent detection are as provided.
The organic electroluminescent diode (OLED) has been studied as an economic
and easy to manufacture source of light (energy). It is an attractive option not only for
the possibility of reducing production costs, but also for the high degree of specificity
it offers with respect to the light wavelength it emits. A device that integrates OLED
in a microfluidic device was reported by Acharya et al. (2015). The proposed LOC
(Fig. 3.3) used an AlQ3 OLED to activate fluorescent dye Alexafluor 488 as part of
a fluorescent assay for bio-optical detection of the antigens. The target antigen was
anti-sheep IgGs, which were fluorescently tagged and were detected via a sandwich
immunoassay after conjugating with monoclonal antibodies (Fig. 3.4). A common
issue when designing such devices is the interference of the light source with the
fluorescence as it may result in bleaching. To avoid such problem, a filter can be
used to allow only certain wavelength of the emitted light to reach the sample and
sensor. The excitation peak of the fluorophore should then be lower than the emission
peak, thus allowing the tag’s fluorescence to accurately reflect the presence of the
antigen. Another concern regarding the OLED source is the inevitable heating of the