Microbial Enzymes in Nanotechnology …
209
system having activation energy of 93.3 kJ/mol, with the concentration of substrate
being relative to the oxidation reaction rate. Also, the NDAus maintained substantial
activities even after a number of reuse and are well matched with a natural enzyme.
Also, Fang et al. (2018) made a needle-type microelectrode which comprises of
copper nanoflowers, nafion, glucose oxidase and polyurethane membranes successfully synthesized via layer-by-layer deposition. The copper nanomaterials created
electrocatalytic activity and a large specific surface area typical of nanomaterials for
glucose detection. The polyurethane layers functioned as mass-transport membranes
which appreciably improved the stability and linearity of sensors. The resulting
biosensor displayed a wide linear range of 0–20 mM, with a high-quality sensitivity
of 42.38 nA mM
−1 and a rapid response time of below 15 s. In vivo experiments using
anesthetized rats displayed outstanding real-time response to the variation of blood
glucose concentration. And the affinity of variation of the sensor output was in agreement with that of glucose meter. The research brought to fore a prospective approach
in applying implantable device for diabetes management in addition to other medical
diagnosis. Wang et al. (2015) reported the synthesis of copper nanoparticles (CuNPs)
produced through a simple and easy annealing process employing humic acid as both
the reducing and stabilizing mediator. The synthesized CuNPs displayed remarkable fundamental peroxidase-like activity, which speedily catalyzed the peroxidase
substrate oxidation, 3,3
,5,5
-tetramethylbenzidine (TMB), in the attendance of H 2 O 2
to create a blue-colored reaction. The H 2 O 2 detection limit by CuNPs can be as small
as 1.32 × 10
−7 M. More significantly, the CuNPs displayed exceptional stability
which was hardly oxidized even after six months. Also, a simple, selective and rapid
colorimetric method for discovering the presence of glucose was developed with
limit of detection of 6.86 × 10
−7 M.
Ionic liquid-coated nanoparticles (IL-NPs) which consisted of zero-valent iron
were reported by Zarif et al. (2018) to present fundamental peroxidase-like activity.
Iron nanoparticles were produced by adding 140 mM sodium borohydride in dropwise manner to 20 mM ferrous sulfate through titration followed leading to formation
of black particles, after which the ionic liquid-coated nanoparticles were prepared.
The IL-NPs produced improved the prospect to mediate the oxidation of the chromogenic substrate 3,3
,5,5
-tetramethylbenzidine (TMB) in the presence of H 2 O 2
which led to the development of a blue green-colored product that was detectable
with bare eyes and quantified by photometry at 652 nm. The IL-NPs were additionally coupled with bismuth to boost its catalytic properties; this also led to
the creation of an easy, responsive and selective colorimetric assay for hydrogen
peroxide. The response obtained was linear in the 30–300 μM H 2 O 2 concentration
range with limit of detection of 0.15 μM. Li et al. (2016a) reported that Pd/Fe 3 O 4 -
PEI-RGO nanohybrid was synthesized by distribution of PdNPs and Fe 3 O 4 NPs
on polyetheylenimine (PEI) modified graphene oxide sheets. This nanohybrid was
observed to display superior peroxidase-like potential, and could competently oxidize
3,3
,5,5
-Tetramethylbenzidine (TMB) by hydrogen peroxide (H 2 O 2 ) to develop a
color reaction. This led to the detection of H 2 O 2 in solution via colorimetric analysis
with linear range obtained for H 2 O 2 being from 0.5 to 150 μM and the limit of detection as small as 0.1 μM. Moreover, simplistic preservation and quick separation of
209
system having activation energy of 93.3 kJ/mol, with the concentration of substrate
being relative to the oxidation reaction rate. Also, the NDAus maintained substantial
activities even after a number of reuse and are well matched with a natural enzyme.
Also, Fang et al. (2018) made a needle-type microelectrode which comprises of
copper nanoflowers, nafion, glucose oxidase and polyurethane membranes successfully synthesized via layer-by-layer deposition. The copper nanomaterials created
electrocatalytic activity and a large specific surface area typical of nanomaterials for
glucose detection. The polyurethane layers functioned as mass-transport membranes
which appreciably improved the stability and linearity of sensors. The resulting
biosensor displayed a wide linear range of 0–20 mM, with a high-quality sensitivity
of 42.38 nA mM
−1 and a rapid response time of below 15 s. In vivo experiments using
anesthetized rats displayed outstanding real-time response to the variation of blood
glucose concentration. And the affinity of variation of the sensor output was in agreement with that of glucose meter. The research brought to fore a prospective approach
in applying implantable device for diabetes management in addition to other medical
diagnosis. Wang et al. (2015) reported the synthesis of copper nanoparticles (CuNPs)
produced through a simple and easy annealing process employing humic acid as both
the reducing and stabilizing mediator. The synthesized CuNPs displayed remarkable fundamental peroxidase-like activity, which speedily catalyzed the peroxidase
substrate oxidation, 3,3
,5,5
-tetramethylbenzidine (TMB), in the attendance of H 2 O 2
to create a blue-colored reaction. The H 2 O 2 detection limit by CuNPs can be as small
as 1.32 × 10
−7 M. More significantly, the CuNPs displayed exceptional stability
which was hardly oxidized even after six months. Also, a simple, selective and rapid
colorimetric method for discovering the presence of glucose was developed with
limit of detection of 6.86 × 10
−7 M.
Ionic liquid-coated nanoparticles (IL-NPs) which consisted of zero-valent iron
were reported by Zarif et al. (2018) to present fundamental peroxidase-like activity.
Iron nanoparticles were produced by adding 140 mM sodium borohydride in dropwise manner to 20 mM ferrous sulfate through titration followed leading to formation
of black particles, after which the ionic liquid-coated nanoparticles were prepared.
The IL-NPs produced improved the prospect to mediate the oxidation of the chromogenic substrate 3,3
,5,5
-tetramethylbenzidine (TMB) in the presence of H 2 O 2
which led to the development of a blue green-colored product that was detectable
with bare eyes and quantified by photometry at 652 nm. The IL-NPs were additionally coupled with bismuth to boost its catalytic properties; this also led to
the creation of an easy, responsive and selective colorimetric assay for hydrogen
peroxide. The response obtained was linear in the 30–300 μM H 2 O 2 concentration
range with limit of detection of 0.15 μM. Li et al. (2016a) reported that Pd/Fe 3 O 4 -
PEI-RGO nanohybrid was synthesized by distribution of PdNPs and Fe 3 O 4 NPs
on polyetheylenimine (PEI) modified graphene oxide sheets. This nanohybrid was
observed to display superior peroxidase-like potential, and could competently oxidize
3,3
,5,5
-Tetramethylbenzidine (TMB) by hydrogen peroxide (H 2 O 2 ) to develop a
color reaction. This led to the detection of H 2 O 2 in solution via colorimetric analysis
with linear range obtained for H 2 O 2 being from 0.5 to 150 μM and the limit of detection as small as 0.1 μM. Moreover, simplistic preservation and quick separation of