Nucleic Acid Based Nanoconstructs for Environmental Analysis …
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have been the cornerstone of industries including pharmaceutical, chemical manufacturing, bio-fuel production and solid waste or water treatment (Li et al. 2012).
Enzymes have found use in two broad aspects of environmental analysis, namely,
detection of specific analytes and small-scale remediation.
Research has sought to develop suitable bio- and macromolecules that can address
the operational constraints of enzymes. DNAzymes and aptazymes are examples
of such artificially engineered moieties. DNAzymes are synthetic analogues of
ribozymes and are DNA molecules that are capable of catalyzing nucleic acid hydrolysis. They have emerged as robust catalysts in their own right and have been adapted
for biosensor applications based on their ability to incorporate nucleic acid secondary
structures that act as receptors for specific analytes. DNAzyme based biosensors for
the detection of toxic metals such as Hg
2+ , (Li et al. 2009) Pb
2+ (Li and Lu 2000;
Shen et al. 2008) and Cu
2+ (Liu and Lu 2007a, b) have been reported. Advances
in transducing nucleic acid interactions through colorimetry, fluorescence, and electrochemical means have been useful in such biosensor development (Zhang et al.
2011). Apart from use as biosensors, enzymes have been comprehensively examined towards environmental remediation. Parathion hydrolase is one example of an
enzyme that has been used for detoxification of water both in free (Munnecke and
Hsieh 1976) and in the immobilized form (Munnecke 1977). Phenol oxidases have
been suggested for the removal of xenobiotics from water. Similarly, horseradish
peroxidase has been successfully used to dephenolize coal-conversion wastewaters.
The enzyme is also effective in removing chlorophenols, chloroanilines, benzidines,
and diphenylanilines (Klibanov et al. 1983).
The use of biomolecules such as enzymes, antibodies or DNAzymes in biosensors for environmental analysis faces a stiff test in terms of robustness and stability
under field testing conditions. Immobilization of the biomolecules on solid supports
is a prominent strategy for addressing these challenges (van de Velde et al. 2002).
The immobilized form of enzymes mimics their natural mode in living cells in many
cases considering their placement and attachment to membranes, organelle structures or the cellular cytoskeleton. The solid supports seek to stabilize the enzymes
while rendering superior mass transfer of analytes thereby contributing to enhanced
robustness and catalytic performance of the overall construct (Datta et al. 2013).
Immobilized biomolecular systems enable greater sophistication in the design of
biosensors thereby helping with their each of use. Enzyme immobilization can also
facilitate enhanced environmental remediation activity. For example, immobilization
of cyanate hydratase on magnetic multi-walled carbon nanotubes has been used for
the simultaneous removal of heavy metal and cyanate in wastewater samples (Ranjan
et al. 2019). An example of sophistication in immobilized enzyme-based approaches
is the adoption of enzyme cascade reactions. Immobilization of enzymes constituting
cascade reactions leads to improved efficiency in the transfer of intermediates from
one step to the next akin to the behavior of complex multi-enzyme complexes underlying several metabolic processes (Schmitt and An 2017). A plethora of strategies
have been devised for the physical and chemical immobilization of biomolecules
on solid supports. In particular, the conjugation of enzymes is often associated with
structural alterations that result in the creation of a distinctive microenvironment of
579
have been the cornerstone of industries including pharmaceutical, chemical manufacturing, bio-fuel production and solid waste or water treatment (Li et al. 2012).
Enzymes have found use in two broad aspects of environmental analysis, namely,
detection of specific analytes and small-scale remediation.
Research has sought to develop suitable bio- and macromolecules that can address
the operational constraints of enzymes. DNAzymes and aptazymes are examples
of such artificially engineered moieties. DNAzymes are synthetic analogues of
ribozymes and are DNA molecules that are capable of catalyzing nucleic acid hydrolysis. They have emerged as robust catalysts in their own right and have been adapted
for biosensor applications based on their ability to incorporate nucleic acid secondary
structures that act as receptors for specific analytes. DNAzyme based biosensors for
the detection of toxic metals such as Hg
2+ , (Li et al. 2009) Pb
2+ (Li and Lu 2000;
Shen et al. 2008) and Cu
2+ (Liu and Lu 2007a, b) have been reported. Advances
in transducing nucleic acid interactions through colorimetry, fluorescence, and electrochemical means have been useful in such biosensor development (Zhang et al.
2011). Apart from use as biosensors, enzymes have been comprehensively examined towards environmental remediation. Parathion hydrolase is one example of an
enzyme that has been used for detoxification of water both in free (Munnecke and
Hsieh 1976) and in the immobilized form (Munnecke 1977). Phenol oxidases have
been suggested for the removal of xenobiotics from water. Similarly, horseradish
peroxidase has been successfully used to dephenolize coal-conversion wastewaters.
The enzyme is also effective in removing chlorophenols, chloroanilines, benzidines,
and diphenylanilines (Klibanov et al. 1983).
The use of biomolecules such as enzymes, antibodies or DNAzymes in biosensors for environmental analysis faces a stiff test in terms of robustness and stability
under field testing conditions. Immobilization of the biomolecules on solid supports
is a prominent strategy for addressing these challenges (van de Velde et al. 2002).
The immobilized form of enzymes mimics their natural mode in living cells in many
cases considering their placement and attachment to membranes, organelle structures or the cellular cytoskeleton. The solid supports seek to stabilize the enzymes
while rendering superior mass transfer of analytes thereby contributing to enhanced
robustness and catalytic performance of the overall construct (Datta et al. 2013).
Immobilized biomolecular systems enable greater sophistication in the design of
biosensors thereby helping with their each of use. Enzyme immobilization can also
facilitate enhanced environmental remediation activity. For example, immobilization
of cyanate hydratase on magnetic multi-walled carbon nanotubes has been used for
the simultaneous removal of heavy metal and cyanate in wastewater samples (Ranjan
et al. 2019). An example of sophistication in immobilized enzyme-based approaches
is the adoption of enzyme cascade reactions. Immobilization of enzymes constituting
cascade reactions leads to improved efficiency in the transfer of intermediates from
one step to the next akin to the behavior of complex multi-enzyme complexes underlying several metabolic processes (Schmitt and An 2017). A plethora of strategies
have been devised for the physical and chemical immobilization of biomolecules
on solid supports. In particular, the conjugation of enzymes is often associated with
structural alterations that result in the creation of a distinctive microenvironment of