90
L. Acosta-Soto and S. Hosseini
A secondary anti-insulin antibody conjugated with a fluorophore was then added to
the system that signaled the presence of the analyte. The PDMS chip showed accurate
readout of insulin in blood plasma within 30s without the need for washing of the
secondary antibody. This allowed a continuous flow and real time detection within
the device.
Although molecular tagging is typically used in fluorescence-based biosensors,
some cells have a fluorescent response to UV exposure as well that can be used for
detection purposes. In a device designed by Onishi et. al. (2017) the fluorescence of
bacteria cells L. pneumophila was used to identify its presence within a sample. To
trap the bacteria cells, they were mixed with micro-beads that helped form a barrier,
or “stopper”, that allowed concentration of bacteria cells to increase dramatically
around the stopper. Once immobilized, the bacteria were exposed to UV radiation
that provided a fluorescent response. This sensor enabled the detection of natural
fluorescent bacteria without the need for optical or elaborate sensors and cameras.
3.5 Alternative BioMEMS for Fluorescence Detection
The feasibility of micro-beads as means to monitor changes in both pH and temperature was investigated by Liu et al. (2014). It was found that by using polystyrene
(PS) micro-beads in combination with two different fluorescent markers (Rhodamine
B and FITC) the fluorescent response of both fluorophores to an excitation source
could be processed to obtain information about the medium in which they were
submerged (Fig. 3.7). The PS micro-spheres were exposed to alcohol, causing them
to swell thus via the open pores, Rhodamine B penetrated and stain the beads. To
capture the Rhodamine B particles, the micro-beads were then rinsed in deionized
water to shrink back the size hence closing the pores. Afterwards, the surface of the
beads was stained with FITC. Since Rhodamine B and FITC have different excitation
ranges, high wavelengths were used to elicit a fluorescent response. To demonstrate
the detection mechanism, the microbeads were analyzed throughout ranges of both
Fig. 3.7 Fabrication process of the micro-beads functionalized with Rhodamine B and FITC (Liu
et al. 2014)
L. Acosta-Soto and S. Hosseini
A secondary anti-insulin antibody conjugated with a fluorophore was then added to
the system that signaled the presence of the analyte. The PDMS chip showed accurate
readout of insulin in blood plasma within 30s without the need for washing of the
secondary antibody. This allowed a continuous flow and real time detection within
the device.
Although molecular tagging is typically used in fluorescence-based biosensors,
some cells have a fluorescent response to UV exposure as well that can be used for
detection purposes. In a device designed by Onishi et. al. (2017) the fluorescence of
bacteria cells L. pneumophila was used to identify its presence within a sample. To
trap the bacteria cells, they were mixed with micro-beads that helped form a barrier,
or “stopper”, that allowed concentration of bacteria cells to increase dramatically
around the stopper. Once immobilized, the bacteria were exposed to UV radiation
that provided a fluorescent response. This sensor enabled the detection of natural
fluorescent bacteria without the need for optical or elaborate sensors and cameras.
3.5 Alternative BioMEMS for Fluorescence Detection
The feasibility of micro-beads as means to monitor changes in both pH and temperature was investigated by Liu et al. (2014). It was found that by using polystyrene
(PS) micro-beads in combination with two different fluorescent markers (Rhodamine
B and FITC) the fluorescent response of both fluorophores to an excitation source
could be processed to obtain information about the medium in which they were
submerged (Fig. 3.7). The PS micro-spheres were exposed to alcohol, causing them
to swell thus via the open pores, Rhodamine B penetrated and stain the beads. To
capture the Rhodamine B particles, the micro-beads were then rinsed in deionized
water to shrink back the size hence closing the pores. Afterwards, the surface of the
beads was stained with FITC. Since Rhodamine B and FITC have different excitation
ranges, high wavelengths were used to elicit a fluorescent response. To demonstrate
the detection mechanism, the microbeads were analyzed throughout ranges of both
Fig. 3.7 Fabrication process of the micro-beads functionalized with Rhodamine B and FITC (Liu
et al. 2014)