elements. The most often reported cell-based biosensors include genetically
modified bacteria with artificially constructed fusions of particular regulatory system
(native promoter) with reporter genes. The presence of an effector (nonspecific such
as DNA damaging agents, heat shock, oxidative stress, toxic metals, organic environmental pollutants) results in transcription and translation of fused target genes,
generating recombinant proteins that produce some measurable response. Frequently
used reporter genes are lux (coding for luciferase) and gfp (coding for green
fluorescence protein), expression of which correlates with luminescence- or
fluorescence-based light emission. Colorimetric determination of target gene expression is possible by fusing it to reporter genes coding for β-galalactosidase (lacZ) or
alkaline phosphatase (phoA). Recently, E. coli biosensor capable of detecting both
genotoxic and oxidative damage has been developed by introducing plasmids with
fusion of katG (gene encoding for an important antioxidative enzyme) promoter to
the lux reporter genes, and another with recA (gene encoding crucial enzyme for
DNA repair) promoter with the gfp reporter gene (Mitchell and Gu 2004). Microbial
biosensors have been widely used in the environmental, food, and diagnostics
industry due to its advantages of low cost, stability, and fast response. Compared
to enzymes, the microorganisms that are used as bioelements can make use of the
enzyme to specifically respond to the analytes without time-consuming and expensive purification. Based on its attractive properties, several directions for the development of the microbial biosensors have shown great promise.
DNA/Nucleic Acid Sensor: Genetic information can be used as a biorecognition
part of various biosensors. Identification of pathogen from a human tissue or blood
samples are common analytes for these biosensors. This biosensor principal is based
on recognition of the complementary strand by ssDNA to form stable hydrogen bond
between two nucleic acids to become dsDNA. In order to achieve this, ssDNA is
used as probe to immobilized in bioreceptor and complementary sequences present
in the target of interest. The highly specific affinity binding’s reaction between target
to the probe’s single strand DNA, which results in hybridization of complementary
ssDNA to form dsDNA. Subsequently biochemical reaction that allows transducer
amplified the signal into electrical one. Sometimes linker such as thiol or biotin is
needed in the effort to immobilize the ssDNA onto the sensing surface. The nucleic
acid biological recognition layer, which incorporates with transducer, is easily
synthesizable, highly specific, and reusable after thermal melting of the DNA duplex
(Fig. 9.2). Moreover, Yeh et al. (2011) have reported optical biochip for bacteria
detection based on DNA hybridization with detection limit of 8.25 ng/ml. However,
electrochemical transduction is the most abandoned method used to study DNA
damage and interaction, as reported in the literature. The development of electrochemical DNA biosensor has received a great deal of attention lately, and this has
largely been driven by the need to develop rapid response, high sensitivity, good
selectivity, and experimental convenience (Liu et al. 2012).
9.2.4.2 Surface Plasmon Resonance (SPR)
The phenomenon of surface plasmon resonance biosensor was first reported by
Wood (1902). The application of biomolecule interaction was first reported by
200
S. Purwar and S. Srivastava
modified bacteria with artificially constructed fusions of particular regulatory system
(native promoter) with reporter genes. The presence of an effector (nonspecific such
as DNA damaging agents, heat shock, oxidative stress, toxic metals, organic environmental pollutants) results in transcription and translation of fused target genes,
generating recombinant proteins that produce some measurable response. Frequently
used reporter genes are lux (coding for luciferase) and gfp (coding for green
fluorescence protein), expression of which correlates with luminescence- or
fluorescence-based light emission. Colorimetric determination of target gene expression is possible by fusing it to reporter genes coding for β-galalactosidase (lacZ) or
alkaline phosphatase (phoA). Recently, E. coli biosensor capable of detecting both
genotoxic and oxidative damage has been developed by introducing plasmids with
fusion of katG (gene encoding for an important antioxidative enzyme) promoter to
the lux reporter genes, and another with recA (gene encoding crucial enzyme for
DNA repair) promoter with the gfp reporter gene (Mitchell and Gu 2004). Microbial
biosensors have been widely used in the environmental, food, and diagnostics
industry due to its advantages of low cost, stability, and fast response. Compared
to enzymes, the microorganisms that are used as bioelements can make use of the
enzyme to specifically respond to the analytes without time-consuming and expensive purification. Based on its attractive properties, several directions for the development of the microbial biosensors have shown great promise.
DNA/Nucleic Acid Sensor: Genetic information can be used as a biorecognition
part of various biosensors. Identification of pathogen from a human tissue or blood
samples are common analytes for these biosensors. This biosensor principal is based
on recognition of the complementary strand by ssDNA to form stable hydrogen bond
between two nucleic acids to become dsDNA. In order to achieve this, ssDNA is
used as probe to immobilized in bioreceptor and complementary sequences present
in the target of interest. The highly specific affinity binding’s reaction between target
to the probe’s single strand DNA, which results in hybridization of complementary
ssDNA to form dsDNA. Subsequently biochemical reaction that allows transducer
amplified the signal into electrical one. Sometimes linker such as thiol or biotin is
needed in the effort to immobilize the ssDNA onto the sensing surface. The nucleic
acid biological recognition layer, which incorporates with transducer, is easily
synthesizable, highly specific, and reusable after thermal melting of the DNA duplex
(Fig. 9.2). Moreover, Yeh et al. (2011) have reported optical biochip for bacteria
detection based on DNA hybridization with detection limit of 8.25 ng/ml. However,
electrochemical transduction is the most abandoned method used to study DNA
damage and interaction, as reported in the literature. The development of electrochemical DNA biosensor has received a great deal of attention lately, and this has
largely been driven by the need to develop rapid response, high sensitivity, good
selectivity, and experimental convenience (Liu et al. 2012).
9.2.4.2 Surface Plasmon Resonance (SPR)
The phenomenon of surface plasmon resonance biosensor was first reported by
Wood (1902). The application of biomolecule interaction was first reported by
200
S. Purwar and S. Srivastava