Microfluidic Systems for Marine Biotechnology 20.3 Microfluidic Devices for Sea-Related Health and Safety 517
Part C | 20.3
high-sensitivity detection system is based on the chemiluminescence reaction of Mn contained in the seawater
sample with a luminol-based reagent. It is composed
of a microdevice for mixing and reaction, a pumping unit, several valving units, and a photomultiplier
(PMT) detector. Mn concentrations above 280 nM in
seawater were detected, and a quite linear response
was obtained until 500 nM. In addition, this device
worked continuously during the 8 h of an actual remotely operated vehicle dive and led to the discovery
of a previously unknown hydrothermal site in the Okinawa Trough.
20.3 Microfluidic Devices for Sea-Related Health and Safety
Microfluidic-based marine biotechnology provides
a promising approach for rapid and accurate in situ
detection of toxic microorganisms, toxins, or pollutants that can threaten human and animal health and
safety.
20.3.1 Microfluidics in Toxic Algae Detection
The detection of algae proliferation in drinking water
and marine recreational water is an important environmental and public health issue. Traditional laboratorybased identification of algae in water requires sophisticated and expensive procedures that result in delays
of effectively reacting to an outbreak. However, increased governmental and public concerns on algaerelated health and safety issues has raised the demands
for low-cost, portable, and real-time algae monitoring. The development of microfluidic devices provides
a promising approach for toxic algae detection. To date,
optical detection [20.93–95], flow cytometry [20.95,
96], electrical impedance [20.97–99], and nucleic acid
amplification [20.38, 100] are successfully exploited on
microfluidic platforms.
Optical detection has been use for algae detection based on shapes, structures, or pigments. Schaap
et al. [20.101, 102] developed a femtosecond laser
to construct a waveguide in a microfluidic device
(Fig. 20.5a) to qualitatively distinguish various algae
types in a water stream by detecting the distinctive
wavelets that are associated with the particular algae
geometry. This sensing principle relies on distorted
transmitted wavelet-like signals induced by an alga
crossing a monochromatic coherent light beam when
moving along a microfluidic channel.
Flow cytometry is a common optical approach used
to detect algae by measuring the a number of optical and
side scatter properties. For example, the ratio of chlorophyll (CHL) to algae size (side scatter signals) and/or to
phycoerythrin (PE) or phycocyanin (PC) has been used
to identify different algae with conventional macroscale
experiments [20.105]. In 2007, Benazzi et al. [20.46]
developed a microfluidic flow cytometry that measures fluorescence, which was used to distinguish three
mixed algae with similar results to those obtained from
a commercial flow cytometry. More recently, Hashemi
et al. [20.103, 106] developed an improved microfluidic flow cytometry for algae species evaluation using
CHL, PE, and side scatter. The chip was composed
of chevron grooves, as shown in Fig. 20.5b, combined
with PDMS-embedded optical fibers, and external optical filters and photomultiplier tubes were used to
collect fluoresced and scattered lights. The device generates a sheath stream that focuses the sample stream
in the center of channel horizontally and reduces the
impact of pulses from the peristaltic pump on the sample stream. The chevron grooves formed on the top
and bottom of channels directs the sheath flow toward
the top and bottom to compress the sample stream
vertically.
Impedance spectroscopy is a noninvasive electrical
method used for measuring size and dielectric characterization of cells when they pass over electrodes
that have an alternating current (AC) potential. This
method has been applied to LOC devices to differentiate cells [20.107, 108]. Benazzi et al. [20.46] developed a microfluidic device integrated with a impedance
spectroscopy and fluorescence measurements to distinguish a mixture of three algae. A microfluidic channel
made from PDMS was placed on a glass substrate
where microelectrodes were patterned (Fig. 20.5c).
Two frequencies (327 kHz and 6:030 MHz) were used
to measure the electrical impedance; the lower frequency was chosen to measure the cell size, while
the higher one was used to probe small changes in
the membrane capacitance of the cells. The magnitude of the electrical impedance signal and fluorescent
measurement were used to resolve three algae species
(Fig. 20.5c).
The detection of harmful marine organisms can
be achieved by using a benchtop isothermal nucleic
acid sequence-based amplification (NASBA) method [20.109]. Recently, a hand-held system integrated
Part C | 20.3
high-sensitivity detection system is based on the chemiluminescence reaction of Mn contained in the seawater
sample with a luminol-based reagent. It is composed
of a microdevice for mixing and reaction, a pumping unit, several valving units, and a photomultiplier
(PMT) detector. Mn concentrations above 280 nM in
seawater were detected, and a quite linear response
was obtained until 500 nM. In addition, this device
worked continuously during the 8 h of an actual remotely operated vehicle dive and led to the discovery
of a previously unknown hydrothermal site in the Okinawa Trough.
20.3 Microfluidic Devices for Sea-Related Health and Safety
Microfluidic-based marine biotechnology provides
a promising approach for rapid and accurate in situ
detection of toxic microorganisms, toxins, or pollutants that can threaten human and animal health and
safety.
20.3.1 Microfluidics in Toxic Algae Detection
The detection of algae proliferation in drinking water
and marine recreational water is an important environmental and public health issue. Traditional laboratorybased identification of algae in water requires sophisticated and expensive procedures that result in delays
of effectively reacting to an outbreak. However, increased governmental and public concerns on algaerelated health and safety issues has raised the demands
for low-cost, portable, and real-time algae monitoring. The development of microfluidic devices provides
a promising approach for toxic algae detection. To date,
optical detection [20.93–95], flow cytometry [20.95,
96], electrical impedance [20.97–99], and nucleic acid
amplification [20.38, 100] are successfully exploited on
microfluidic platforms.
Optical detection has been use for algae detection based on shapes, structures, or pigments. Schaap
et al. [20.101, 102] developed a femtosecond laser
to construct a waveguide in a microfluidic device
(Fig. 20.5a) to qualitatively distinguish various algae
types in a water stream by detecting the distinctive
wavelets that are associated with the particular algae
geometry. This sensing principle relies on distorted
transmitted wavelet-like signals induced by an alga
crossing a monochromatic coherent light beam when
moving along a microfluidic channel.
Flow cytometry is a common optical approach used
to detect algae by measuring the a number of optical and
side scatter properties. For example, the ratio of chlorophyll (CHL) to algae size (side scatter signals) and/or to
phycoerythrin (PE) or phycocyanin (PC) has been used
to identify different algae with conventional macroscale
experiments [20.105]. In 2007, Benazzi et al. [20.46]
developed a microfluidic flow cytometry that measures fluorescence, which was used to distinguish three
mixed algae with similar results to those obtained from
a commercial flow cytometry. More recently, Hashemi
et al. [20.103, 106] developed an improved microfluidic flow cytometry for algae species evaluation using
CHL, PE, and side scatter. The chip was composed
of chevron grooves, as shown in Fig. 20.5b, combined
with PDMS-embedded optical fibers, and external optical filters and photomultiplier tubes were used to
collect fluoresced and scattered lights. The device generates a sheath stream that focuses the sample stream
in the center of channel horizontally and reduces the
impact of pulses from the peristaltic pump on the sample stream. The chevron grooves formed on the top
and bottom of channels directs the sheath flow toward
the top and bottom to compress the sample stream
vertically.
Impedance spectroscopy is a noninvasive electrical
method used for measuring size and dielectric characterization of cells when they pass over electrodes
that have an alternating current (AC) potential. This
method has been applied to LOC devices to differentiate cells [20.107, 108]. Benazzi et al. [20.46] developed a microfluidic device integrated with a impedance
spectroscopy and fluorescence measurements to distinguish a mixture of three algae. A microfluidic channel
made from PDMS was placed on a glass substrate
where microelectrodes were patterned (Fig. 20.5c).
Two frequencies (327 kHz and 6:030 MHz) were used
to measure the electrical impedance; the lower frequency was chosen to measure the cell size, while
the higher one was used to probe small changes in
the membrane capacitance of the cells. The magnitude of the electrical impedance signal and fluorescent
measurement were used to resolve three algae species
(Fig. 20.5c).
The detection of harmful marine organisms can
be achieved by using a benchtop isothermal nucleic
acid sequence-based amplification (NASBA) method [20.109]. Recently, a hand-held system integrated