Antibodies and antigens are examples of biomolecules possessing piezoelectric
effect. The biological sensing element experiences mechanical and electrical forces
on application of acoustic wave. These acoustic waves are generated by applying
alternating voltage to the electrodes attached to the surface of the piezoelectric
substrate. A bio-sensing element interacting with the acoustic wave, results in a
change in the viscosity, density, elasticity or the dielectric constant of the sensing
element. This modifies the properties of the acoustic wave and results in the change
of velocity or frequency of the propagating acoustic wave. Attenuation in the
amplitude of the wave may also result. The piezoelectric element is responsible for
relaying this change in the form of an electrical signal.
Based on the bio-sensing material, piezoelectric biosensor are further classified
into following subtypes as discussed below:
Piezoelectric Immunosensors: The primary bio-sensing elements used in this type
of piezoelectric sensor are antibodies. The detection of antibody is label-free, and
these type of sensors are reusable. Successful detection of human cells like
T-lymphocytes [63], bacteria such as E.coli [64] are noteworthy examples of
piezoelectric immunosensors.
Piezoelectric DNA Sensors: DNA based piezoelectric sensors provide higher
selectivity and reliability. However, the immobilization of DNA is a complex task.
The identification of Genetic defects with a TSM biosensor [65] and enzymatic
cleavage monitoring of nucleic acids in real time [66] are some examples of
Piezoelectric DNA Sensors.
Piezoelectric Enzyme Sensors: The bio-catalytic activity of enzymes specifically in
the bio-reactions is very well suited for a broad range of applications. Enzyme
based piezoelectric sensor are found useful in detecting bio-catalytic activity.
Enzymes are easily immobilized and are abundantly found. Piezoelectric glucose
meter [67] is an important example in this category of the biosensor.
Piezoelectric cell-based Sensors. This type of sensor works in conjunction with
living cells as the bio-sensing element. Cell-based piezoelectric sensors are useful in
revealing functional information, for example, the effect of an analyte on a living
cell. Other useful applications of this type of sensors lie in the area of environmental
measurements, cell biology and toxicology [68].
4 Nanomaterials Based Biosensors
Different types of nanomaterials such as nanocube, nanoshell and nanorod have
been used for analytical purposes [69]. The light scattering properties of various
nanomaterials have been employed for the identification of various analytes. The
scattering properties of nanomaterials are based on size, composition and shape of
the nanoparticle. The efficiency of detection is comparable to the fluorescent label
Materials in Bio-Sensing of Water Pollutants
199
effect. The biological sensing element experiences mechanical and electrical forces
on application of acoustic wave. These acoustic waves are generated by applying
alternating voltage to the electrodes attached to the surface of the piezoelectric
substrate. A bio-sensing element interacting with the acoustic wave, results in a
change in the viscosity, density, elasticity or the dielectric constant of the sensing
element. This modifies the properties of the acoustic wave and results in the change
of velocity or frequency of the propagating acoustic wave. Attenuation in the
amplitude of the wave may also result. The piezoelectric element is responsible for
relaying this change in the form of an electrical signal.
Based on the bio-sensing material, piezoelectric biosensor are further classified
into following subtypes as discussed below:
Piezoelectric Immunosensors: The primary bio-sensing elements used in this type
of piezoelectric sensor are antibodies. The detection of antibody is label-free, and
these type of sensors are reusable. Successful detection of human cells like
T-lymphocytes [63], bacteria such as E.coli [64] are noteworthy examples of
piezoelectric immunosensors.
Piezoelectric DNA Sensors: DNA based piezoelectric sensors provide higher
selectivity and reliability. However, the immobilization of DNA is a complex task.
The identification of Genetic defects with a TSM biosensor [65] and enzymatic
cleavage monitoring of nucleic acids in real time [66] are some examples of
Piezoelectric DNA Sensors.
Piezoelectric Enzyme Sensors: The bio-catalytic activity of enzymes specifically in
the bio-reactions is very well suited for a broad range of applications. Enzyme
based piezoelectric sensor are found useful in detecting bio-catalytic activity.
Enzymes are easily immobilized and are abundantly found. Piezoelectric glucose
meter [67] is an important example in this category of the biosensor.
Piezoelectric cell-based Sensors. This type of sensor works in conjunction with
living cells as the bio-sensing element. Cell-based piezoelectric sensors are useful in
revealing functional information, for example, the effect of an analyte on a living
cell. Other useful applications of this type of sensors lie in the area of environmental
measurements, cell biology and toxicology [68].
4 Nanomaterials Based Biosensors
Different types of nanomaterials such as nanocube, nanoshell and nanorod have
been used for analytical purposes [69]. The light scattering properties of various
nanomaterials have been employed for the identification of various analytes. The
scattering properties of nanomaterials are based on size, composition and shape of
the nanoparticle. The efficiency of detection is comparable to the fluorescent label
Materials in Bio-Sensing of Water Pollutants
199