proves to be an efficient label-free method with reusability for pathogen detection, as
compared to the other abovementioned methods.
10.3.3 Piezoelectric Biosensors
10.3.3.1 Piezoelectric Quartz Crystal Biosensors
Piezoelectric quartz crystal-based biosensors employ the specific attachment of a
target biomolecule leading to mass change which can be detected by the equivalent
variations in electrical/acoustic properties (Alder and McCallum 1983) of the piezoelectric quartz crystal. It involves a simple methodology without any sample preparation or detection labels (Arlett et al. 2011). Quartz crystal is the mainly used
piezoelectric material (Deakin and Buttry 1989), for it has desirable electromechanical and chemical properties. A proportional relation exists between differences in
crystal mass and its resonance which is exploited for pathogen detection in these
biosensors.
There exists two modes of pathogen detection (Farka et al. 2013) in piezoelectric
biosensors, namely, active mode or passive mode. Active mode works by wavering of
the piezoelectric crystal with corresponding resonance frequency differences monitored by frequency counter (Arnau 2008), while the passive mode piezoelectric
biosensor (Zhang et al. 2002) employs an equipment to observe the changes in
mass/viscosity as a result of binding of analyte on sensor surface (Itoh and Ichihashi
2008).
A series-piezoelectric quartz crystal biosensor was developed for S. aureus detection (Lian et al. 2015), which uses graphene-layered interdigital gold electrodes
arranged in series with piezoelectric quartz crystal, upon which aptamers/antibodies
specific to the targeted pathogen were fixed as probe molecules for the detection of
appropriate pathogens. Here, the targeted pathogenic DNA (i.e., S. aureus)
hybridizes selectively to the aptamer probes, depleting the binding forces of aptamer
with graphene (Shi et al. 2017). This ultimately results in variations of electrical
features at the surface of the electrode and appropriate differences in oscillation
frequencies yielding a detection limit of pathogen of 41 cfu/ml. Likewise, using an
antimicrobial peptide probe, pleurocidin, and a transducer made of a single-walled
carbon nanotubes/interdigital electrode, a multichannel series piezoelectric quartz
crystal-based biosensor was developed for rapid multiple microbial detection including S. aureus, Pseudomonas aeruginosa, Enterococcus faecalis, Streptococcus
pneumoniae, Klebsiella pneumonia, Enterobacter cloacae, E. coli, and Candida
albicans within time period of 15 minutes (Shi et al. 2017). This biosensor finds its
significance in clinical diagnosis(Jordana-Lluch et al. 2013) and food safety
measures (Farahi et al. 2012). Here, the probe pleurocidin binds with target microbe
causing detachment of pleurocidin from the carbon nanotubes, consequently changing the resistance of the electrodes and frequency variation of piezoelectric crystal. It
is applicable for all microbes to be detected, considered as the first step for the
screening of microbial blood stream infection (Gonsalves and Sakr 2010) and for
testing microbial drug susceptibility. It is significant to note that enhanced sensitivity
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J. Brindha et al.
compared to the other abovementioned methods.
10.3.3 Piezoelectric Biosensors
10.3.3.1 Piezoelectric Quartz Crystal Biosensors
Piezoelectric quartz crystal-based biosensors employ the specific attachment of a
target biomolecule leading to mass change which can be detected by the equivalent
variations in electrical/acoustic properties (Alder and McCallum 1983) of the piezoelectric quartz crystal. It involves a simple methodology without any sample preparation or detection labels (Arlett et al. 2011). Quartz crystal is the mainly used
piezoelectric material (Deakin and Buttry 1989), for it has desirable electromechanical and chemical properties. A proportional relation exists between differences in
crystal mass and its resonance which is exploited for pathogen detection in these
biosensors.
There exists two modes of pathogen detection (Farka et al. 2013) in piezoelectric
biosensors, namely, active mode or passive mode. Active mode works by wavering of
the piezoelectric crystal with corresponding resonance frequency differences monitored by frequency counter (Arnau 2008), while the passive mode piezoelectric
biosensor (Zhang et al. 2002) employs an equipment to observe the changes in
mass/viscosity as a result of binding of analyte on sensor surface (Itoh and Ichihashi
2008).
A series-piezoelectric quartz crystal biosensor was developed for S. aureus detection (Lian et al. 2015), which uses graphene-layered interdigital gold electrodes
arranged in series with piezoelectric quartz crystal, upon which aptamers/antibodies
specific to the targeted pathogen were fixed as probe molecules for the detection of
appropriate pathogens. Here, the targeted pathogenic DNA (i.e., S. aureus)
hybridizes selectively to the aptamer probes, depleting the binding forces of aptamer
with graphene (Shi et al. 2017). This ultimately results in variations of electrical
features at the surface of the electrode and appropriate differences in oscillation
frequencies yielding a detection limit of pathogen of 41 cfu/ml. Likewise, using an
antimicrobial peptide probe, pleurocidin, and a transducer made of a single-walled
carbon nanotubes/interdigital electrode, a multichannel series piezoelectric quartz
crystal-based biosensor was developed for rapid multiple microbial detection including S. aureus, Pseudomonas aeruginosa, Enterococcus faecalis, Streptococcus
pneumoniae, Klebsiella pneumonia, Enterobacter cloacae, E. coli, and Candida
albicans within time period of 15 minutes (Shi et al. 2017). This biosensor finds its
significance in clinical diagnosis(Jordana-Lluch et al. 2013) and food safety
measures (Farahi et al. 2012). Here, the probe pleurocidin binds with target microbe
causing detachment of pleurocidin from the carbon nanotubes, consequently changing the resistance of the electrodes and frequency variation of piezoelectric crystal. It
is applicable for all microbes to be detected, considered as the first step for the
screening of microbial blood stream infection (Gonsalves and Sakr 2010) and for
testing microbial drug susceptibility. It is significant to note that enhanced sensitivity
280
J. Brindha et al.