Microbial Enzymes in Nanotechnology …
211
thus facilitated visual recognition of presence of E. coli O157:H7 even without
instrumentation. By reason of the outstanding peroxidase activity of Pt–AuNPs,
they emit powerful visible color intensity in under 1 min for visual examination even
at low concentration range of E. coli O157:H7. Estimation carried out by means of a
commercial assay meter recorded that the susceptibility was better and above 1000
folds relative to the normal test strip founded on colored gold colloids. It was opined
that this technique could effortlessly be developed to be a general signal amplification method and used for foodborne pathogens detection in addition to protein
biomarkers.
Some metallic oxide-based nanomaterials have also been described to have
peroxidase mimetic potentials. Liu et al. (2017a) reported that ceria or cerium
dioxide nanoparticle functionalized by porphyrin (Por-Ceria) was fabricated by a
one-step technique by reacting 0.04 M cerium (III) nitrate with 0.125 mM 20tetrakis(4-carboxyl pheyl)-porphyrin (H 2 TCPP), after which 200 μL H 2 O 2 was
injected, and then heat was applied. The porphyrin-functionalized ceria nanoparticles were exploited as a probe in colorimetric detection for H 2 O 2 . Por-Ceria
nanoparticles exhibited powerful inherent peroxidase potential against 3,3
,5,5
-
tetramethylbenzidine (TMB), in the coexistence of H 2 O 2 . It was observed that
improved peroxidase-like potential of Por-Ceria was in consequent of the synergistic result of ceria and porphyrin, thus establishing the elevated performance of
Por-Ceria as a synthetic peroxidase mimic. Also, when Por-Ceria was integrated
with glucose oxidase, glucose detection was achieved and a limit of detection of 1.9
× 10
−2 mM glucose with a linear range up to 0.15 mM was obtained. According to
Deng et al. (2017), CuO nanoparticles were synthesized using quick-precipitation
method with 0.02 M aqueous copper acetate solution as precausor. It was observed
that inherent alkaline peroxidase-like potency was demonstrated by CuO nanoparticles when 3-(4-hydroxyphenyl) propionic acid was utilized as a substrate. From
the result, a fluorometric assay with a limit of detection as little as 0.81 μM was
authenticated for H 2 O 2 under alkaline conditions. However, ammonia was observed
to hinder the alkaline peroxidase-like potentials of the CuO nanoparticles. Thus, a
sensing package for ascertaining of urease and urea was successfully constructed,
with the detection limits for urea and urease being 27 μM and 2.6 U/l, correspondingly. The sensing technique was subsequently applied for identification of urea and
urease in human urine and soil, respectively, which yielded acceptable results.
Furthermore, Guo et al. (2017b) reported that Hemin–MnO 2 nanocomposite was
used as the label for human immunoglobulin G in an enzyme-linked immunosorbent assay (ELISA). Hemin-MnO 2 nanocomposite was synthesized by using hemin
treated with 10 mM of aqueous phosphate buffer, and 50 μl of aqueous ammonia
which was reacted with 100 mM manganese acetate. Improved sensitivity was
recorded attributable to the better catalytic activity of the hemin-MnO 2 nanocomposite to 3,3
,5,5
-tetramethylbenzidine when related to MnO 2 and hemin separately. After assembly of the sandwich-type immunoassay in the 96 wells of the
plate, the hemin–MnO 2 -based label catalyzed 3,3
,5,5
-tetramethylbenzidine into
blue compounds that were monitored by a plate reader. The absorbance correspondingly rise with human immunoglobulin G concentration. The immunoassay was also
211
thus facilitated visual recognition of presence of E. coli O157:H7 even without
instrumentation. By reason of the outstanding peroxidase activity of Pt–AuNPs,
they emit powerful visible color intensity in under 1 min for visual examination even
at low concentration range of E. coli O157:H7. Estimation carried out by means of a
commercial assay meter recorded that the susceptibility was better and above 1000
folds relative to the normal test strip founded on colored gold colloids. It was opined
that this technique could effortlessly be developed to be a general signal amplification method and used for foodborne pathogens detection in addition to protein
biomarkers.
Some metallic oxide-based nanomaterials have also been described to have
peroxidase mimetic potentials. Liu et al. (2017a) reported that ceria or cerium
dioxide nanoparticle functionalized by porphyrin (Por-Ceria) was fabricated by a
one-step technique by reacting 0.04 M cerium (III) nitrate with 0.125 mM 20tetrakis(4-carboxyl pheyl)-porphyrin (H 2 TCPP), after which 200 μL H 2 O 2 was
injected, and then heat was applied. The porphyrin-functionalized ceria nanoparticles were exploited as a probe in colorimetric detection for H 2 O 2 . Por-Ceria
nanoparticles exhibited powerful inherent peroxidase potential against 3,3
,5,5
-
tetramethylbenzidine (TMB), in the coexistence of H 2 O 2 . It was observed that
improved peroxidase-like potential of Por-Ceria was in consequent of the synergistic result of ceria and porphyrin, thus establishing the elevated performance of
Por-Ceria as a synthetic peroxidase mimic. Also, when Por-Ceria was integrated
with glucose oxidase, glucose detection was achieved and a limit of detection of 1.9
× 10
−2 mM glucose with a linear range up to 0.15 mM was obtained. According to
Deng et al. (2017), CuO nanoparticles were synthesized using quick-precipitation
method with 0.02 M aqueous copper acetate solution as precausor. It was observed
that inherent alkaline peroxidase-like potency was demonstrated by CuO nanoparticles when 3-(4-hydroxyphenyl) propionic acid was utilized as a substrate. From
the result, a fluorometric assay with a limit of detection as little as 0.81 μM was
authenticated for H 2 O 2 under alkaline conditions. However, ammonia was observed
to hinder the alkaline peroxidase-like potentials of the CuO nanoparticles. Thus, a
sensing package for ascertaining of urease and urea was successfully constructed,
with the detection limits for urea and urease being 27 μM and 2.6 U/l, correspondingly. The sensing technique was subsequently applied for identification of urea and
urease in human urine and soil, respectively, which yielded acceptable results.
Furthermore, Guo et al. (2017b) reported that Hemin–MnO 2 nanocomposite was
used as the label for human immunoglobulin G in an enzyme-linked immunosorbent assay (ELISA). Hemin-MnO 2 nanocomposite was synthesized by using hemin
treated with 10 mM of aqueous phosphate buffer, and 50 μl of aqueous ammonia
which was reacted with 100 mM manganese acetate. Improved sensitivity was
recorded attributable to the better catalytic activity of the hemin-MnO 2 nanocomposite to 3,3
,5,5
-tetramethylbenzidine when related to MnO 2 and hemin separately. After assembly of the sandwich-type immunoassay in the 96 wells of the
plate, the hemin–MnO 2 -based label catalyzed 3,3
,5,5
-tetramethylbenzidine into
blue compounds that were monitored by a plate reader. The absorbance correspondingly rise with human immunoglobulin G concentration. The immunoassay was also