was reported for early M. tuberculosis detection using this piezoelectric quartz
crystal-based biosensor than other methods (Zheng et al. 2007; Li et al. 2009).
10.3.3.2 Piezoelectric Cantilever Biosensors
Cantilevers denote the non-flexible structural elements that are fixed at one end of a
solid firm support. Piezoelectric biosensors use biological receptors conjugated to
the micro-cantilevers, that possess distinct resonance frequencies that respond on
binding of target analytes in the sample, with mass increase or mechanical stress on
the cantilever (Ahmed et al. 2014). This change in cantilever property is used for
many pathogenic bacterial detection such as E. coli O157:H7 (Zhang and Hai-Feng
2004; Campbell and Mutharasan 2005a), S. typhimurium (Zhu et al. 2007), and
Francisella tularensis (Ji et al. 2004) (a biowarfare agent). Detection of various
bacteria like E. coli (Campbell and Mutharasan 2007) and L. monocytogenes in milk
samples (Sharma and Mutharasan 2013) have been made possible using specific
antibody bound to cantilevers excited by piezoelectricity. E. coli O157:H7 detection
up to a minimum of 700 cells/ml is reported using cantilevers bound to specific
monoclonal antibody of pathogen targeted (Campbell and Mutharasan 2005b).
Impedance analyzers are employed to monitor the resonance frequency changes
and thereby the concentration of targeted pathogen by the selective binding to
specific antibody at the cantilever tips. Amplitude ratio and phase angle variations
proportional to changes mass/mechanical stress were monitored with the help of an
impedance analyzer (Campbell and Mutharasan 2006).
These piezoelectric cantilever biosensors are also used for specific virulence
hemolysin
gene,
hlyA
(DNA/gene)-based
detection
of
pathogen,
L. monocytogenes, using specific probes bound to a cantilever, detected with a
fluorescent indicator and gold nanoparticles bound to secondary single-stranded
DNA for hybridization signal amplification (Sankaranarayanan et al. 2015). It proves
to be rapid relative to other typical pathogen detection strategies.
10.3.4 Electrochemical Biosensors
Electrochemical biosensors use the changes in electrical properties such as current,
voltage, or impedance/resistance at the electrode surface on binding of biological
analytes including pathogens/biomolecules in a test sample. On the basis of principle
of detection and the electrical properties, they are classified as impedimetric/conductometric and amperometric/voltammetric biosensors.
It also involves another two subtypes including labeled and label-free electrochemical biosensors (Xu et al. 2017) on the basis of usage of labels such as enzymes
and nanoparticles (Fei et al. 2015; Xiang et al. 2015) bound to the targeted bioanalyte
in the case of labeled biosensors. However, the label-free method operates in the
absence of any bound labels, based on interaction of bacterial cells at the electrode
surface (Sang et al. 2016), that are discussed side by side along with other biosensor
developments.
10 Environment Remediation Tools: Chemosensors and Biosensors
281
crystal-based biosensor than other methods (Zheng et al. 2007; Li et al. 2009).
10.3.3.2 Piezoelectric Cantilever Biosensors
Cantilevers denote the non-flexible structural elements that are fixed at one end of a
solid firm support. Piezoelectric biosensors use biological receptors conjugated to
the micro-cantilevers, that possess distinct resonance frequencies that respond on
binding of target analytes in the sample, with mass increase or mechanical stress on
the cantilever (Ahmed et al. 2014). This change in cantilever property is used for
many pathogenic bacterial detection such as E. coli O157:H7 (Zhang and Hai-Feng
2004; Campbell and Mutharasan 2005a), S. typhimurium (Zhu et al. 2007), and
Francisella tularensis (Ji et al. 2004) (a biowarfare agent). Detection of various
bacteria like E. coli (Campbell and Mutharasan 2007) and L. monocytogenes in milk
samples (Sharma and Mutharasan 2013) have been made possible using specific
antibody bound to cantilevers excited by piezoelectricity. E. coli O157:H7 detection
up to a minimum of 700 cells/ml is reported using cantilevers bound to specific
monoclonal antibody of pathogen targeted (Campbell and Mutharasan 2005b).
Impedance analyzers are employed to monitor the resonance frequency changes
and thereby the concentration of targeted pathogen by the selective binding to
specific antibody at the cantilever tips. Amplitude ratio and phase angle variations
proportional to changes mass/mechanical stress were monitored with the help of an
impedance analyzer (Campbell and Mutharasan 2006).
These piezoelectric cantilever biosensors are also used for specific virulence
hemolysin
gene,
hlyA
(DNA/gene)-based
detection
of
pathogen,
L. monocytogenes, using specific probes bound to a cantilever, detected with a
fluorescent indicator and gold nanoparticles bound to secondary single-stranded
DNA for hybridization signal amplification (Sankaranarayanan et al. 2015). It proves
to be rapid relative to other typical pathogen detection strategies.
10.3.4 Electrochemical Biosensors
Electrochemical biosensors use the changes in electrical properties such as current,
voltage, or impedance/resistance at the electrode surface on binding of biological
analytes including pathogens/biomolecules in a test sample. On the basis of principle
of detection and the electrical properties, they are classified as impedimetric/conductometric and amperometric/voltammetric biosensors.
It also involves another two subtypes including labeled and label-free electrochemical biosensors (Xu et al. 2017) on the basis of usage of labels such as enzymes
and nanoparticles (Fei et al. 2015; Xiang et al. 2015) bound to the targeted bioanalyte
in the case of labeled biosensors. However, the label-free method operates in the
absence of any bound labels, based on interaction of bacterial cells at the electrode
surface (Sang et al. 2016), that are discussed side by side along with other biosensor
developments.
10 Environment Remediation Tools: Chemosensors and Biosensors
281