optical probes. The metal nanoparticles with a diameter greater than 30 nm have the
strong light-scattering ability in the visible region. However, smaller nanoparticles
do not exhibit scattering but can be used for detection of different types of chemical
interactions such as avidin-biotin, antigen-antibody electrostatic attraction and
DNA hybridization. These small size nanoparticles can assist in detection when
they aggregate due to these interactions.
An application of nano-biosensors for identification of wastewater pollutants is
urea detection. Nanosized porous alumina was used which was fabricated by the
use of electrical anodization in acidic solution. Nano-alumina porous matrix was
used as an immobilization system for bio-colloidal systems. The use of nanosized
materials increases the surface area, which leads to enhanced sensitivity. Other
workers have fabricated urea biosensor using lipid bilayer membranes [70],
hydrogel membranes [71] and other inorganic matrices such as laponite and clays
[69]. The interaction between the nanomaterials and proteins with opposite charges
causes enhancement of light scattering signals. Thus the electrostatic attraction
between the protein and metallic or non-metallic nanomaterials can increase the
sensitivity to nanograms. Researchers have suggested the use of gold nanoparticles
for the detection of heavy metals. The colorimetric based detection depends on the
light scattering property of gold nanoparticles. Priyadarshini et al. have studied the
effect of gold nanoparticles in metal ions detector. This strategy is applicable for the
identification of heavy metals such as arsenic, mercury, chromium, copper, cadmium, lead, alkaline earth metals and rare elements [72].
Cadmium contamination is found in wastewater, which poses health risks. Some
researchers have co-functionalised the gold nanoparticles with L-Cysteine and
6-mercaptonicotinic acid to develop a biosensor with high sensitivity for cadmium
detection [73]. Another colorimetric detection method of heavy metals using
peptide-modified gold nanoparticles was developed. The functional peptide ligand
was used for the sensitive detection of three heavy metals such as nickel, cadmium
and cobalt. This biosensor had the provision of simultaneous detection of the three
metals existing together in the sample. The detection of cadmium was carried out by
the use of EDTA and imidazole for masking of cobalt and nickel. For nickel
detection, EDTA and glutathione were applied to mask cobalt and cadmium
whereas imidazole and glutathione were used for masking the effect of nickel and
cadmium. Thus, water quality can be assessed with the help of this strategy without
complex preparation [74].
5 Application of Biosensors in the Detection of Water
Pollutants
The constituents of wastewater pollutants can be broadly classified into three types
(i) inorganic chemicals (ii) organic chemicals and (iii) microorganisms. Due to the
advantages associated with biosensors, they have been employed in the detection of
200
R. Sinha et al.
strong light-scattering ability in the visible region. However, smaller nanoparticles
do not exhibit scattering but can be used for detection of different types of chemical
interactions such as avidin-biotin, antigen-antibody electrostatic attraction and
DNA hybridization. These small size nanoparticles can assist in detection when
they aggregate due to these interactions.
An application of nano-biosensors for identification of wastewater pollutants is
urea detection. Nanosized porous alumina was used which was fabricated by the
use of electrical anodization in acidic solution. Nano-alumina porous matrix was
used as an immobilization system for bio-colloidal systems. The use of nanosized
materials increases the surface area, which leads to enhanced sensitivity. Other
workers have fabricated urea biosensor using lipid bilayer membranes [70],
hydrogel membranes [71] and other inorganic matrices such as laponite and clays
[69]. The interaction between the nanomaterials and proteins with opposite charges
causes enhancement of light scattering signals. Thus the electrostatic attraction
between the protein and metallic or non-metallic nanomaterials can increase the
sensitivity to nanograms. Researchers have suggested the use of gold nanoparticles
for the detection of heavy metals. The colorimetric based detection depends on the
light scattering property of gold nanoparticles. Priyadarshini et al. have studied the
effect of gold nanoparticles in metal ions detector. This strategy is applicable for the
identification of heavy metals such as arsenic, mercury, chromium, copper, cadmium, lead, alkaline earth metals and rare elements [72].
Cadmium contamination is found in wastewater, which poses health risks. Some
researchers have co-functionalised the gold nanoparticles with L-Cysteine and
6-mercaptonicotinic acid to develop a biosensor with high sensitivity for cadmium
detection [73]. Another colorimetric detection method of heavy metals using
peptide-modified gold nanoparticles was developed. The functional peptide ligand
was used for the sensitive detection of three heavy metals such as nickel, cadmium
and cobalt. This biosensor had the provision of simultaneous detection of the three
metals existing together in the sample. The detection of cadmium was carried out by
the use of EDTA and imidazole for masking of cobalt and nickel. For nickel
detection, EDTA and glutathione were applied to mask cobalt and cadmium
whereas imidazole and glutathione were used for masking the effect of nickel and
cadmium. Thus, water quality can be assessed with the help of this strategy without
complex preparation [74].
5 Application of Biosensors in the Detection of Water
Pollutants
The constituents of wastewater pollutants can be broadly classified into three types
(i) inorganic chemicals (ii) organic chemicals and (iii) microorganisms. Due to the
advantages associated with biosensors, they have been employed in the detection of
200
R. Sinha et al.