210
J. A. Elegbede and A. Lateef
the nanohybrids were observed to be advantageous, and while comparing with other
catalysts (Fe 3 O 4 -PEI-RGO, PEI-RGO and Pd-PEI-RGO), the nanohybrid exhibited
enhanced peroxidase catalytic activity.
Platinum nanoclusters (PtNCs) were synthesized via an easy one-pot technique
using yeast extract as both reductant and stabilizer as reported by Jin et al. (2017).
Asides from their outstanding water solubility, the yeast extract-stabilized PtNCs also
possess attractive peroxidase-mimicking property. The PtNCs efficiently catalyzed
3,3,5,5-tetramethylbenzidine (TMB) oxidation in the coexistence of H 2 O 2 . Catalytic
mechanism analysis proposed that the peroxidase-mimicking potential of the PtNCs
was like on account of their characteristic of speeding up electron transfer between
TMB and H 2 O 2 , and their enzymatic kinetics was in accordance with the typical
Michaelis–Menten theory. A highly responsive colorimetric system for detection of
glucose was produced, and the limit of detection was estimated as little as 0.28 μM.
The system was further applied for discovery of glucose in human blood serum and
was successfully demonstrated, which suggested its promising use as peroxidase
imitators in pharmaceuticals, clinical diagnosis and environmental chemistry. Li et al.
(2015) described the production of glutathione (GSH)-capped platinum nanoparticles
by dissolving different concentrations of GSH (1–300 mM) in 10 mM PBS buffer (pH
5.0), then mixed with 300 mM K 2 PtCl4 and incubated for 2 h at 25 °C. Then freshly
prepared dimethylamine borane (DMAB) aqueous solution was mixed to the above
mixture for a 12 h-reduction at 25 °C. The GSH-capped PtNPs displayed activity
as peroxidase imitator which ranged from 2.3 to 3.6 nm. The limit of detection was
as little as 0.25 nM by using GSH-Pt having mean diameter of 3.6 nm. GSH-Pt
was reiterated as a capable component for colorimetric detection of Hg
2+ in both
drinkable water and biological fluids.
Some bimetallic nanomaterials have also been described to display peroxidase
mimetic potentials. Li et al. (2016b) found that cysteine-rich metallothioneins (MTs)
could improve the peroxidase mimic activity of citrate-capped AuNPs coated with
traces of mercury (AuNPs-Hg). The AuNPs with mean size of 13 nm were fabricated
by the citrate reduction method using 1 mM HAuCl 4 solution as a precausor. The
AuNPs accumulated by the cysteine-rich metallothioneins (AuNP-Hg-MTs) successfully catalyzed H 2 O 2 -mediated oxidation of 2,2
-azino-bis(3-ethylbenzothiazoline6sulfonate) (ABTS). This led to a color change and subsequent absorbance at 416 nm
which linearly corresponded to the concentration of MTs in the 4.3–49 nM range,
and the limit of detection was 1.3 nM. Thus, the technique was effectively applied
to determine MTs in (spiked) human urine. Jiang et al. (2016) produced a new
immunochromatographic assay (ICA) with improved sensitivity for both quantitative and visual exposure of E. coli O157:H7. Sandwich-type immunoreactions
were carried out on the immunochromatographic assay, and platinum–gold bimetal
nanoparticles (Pt–Au NPs) were aggregated on the test area. The Pt–AuNPs was fabricated by ultrasonically dissolving Pluronic F127 (10 mg) into 1.0 ml of a solution
containing K 2 PtCl 4 (20 mM), HAuCl 4 (20 mM) and HCl (6 M), and using ascorbic
acid as reducing substance while further washed with bovine serum albumin. The
signal amplification was based on Pt–AuNPs having high peroxidase activity toward
3,3
,5,5
-tetramethylbenzidine, which produced characteristic-colored signals and
J. A. Elegbede and A. Lateef
the nanohybrids were observed to be advantageous, and while comparing with other
catalysts (Fe 3 O 4 -PEI-RGO, PEI-RGO and Pd-PEI-RGO), the nanohybrid exhibited
enhanced peroxidase catalytic activity.
Platinum nanoclusters (PtNCs) were synthesized via an easy one-pot technique
using yeast extract as both reductant and stabilizer as reported by Jin et al. (2017).
Asides from their outstanding water solubility, the yeast extract-stabilized PtNCs also
possess attractive peroxidase-mimicking property. The PtNCs efficiently catalyzed
3,3,5,5-tetramethylbenzidine (TMB) oxidation in the coexistence of H 2 O 2 . Catalytic
mechanism analysis proposed that the peroxidase-mimicking potential of the PtNCs
was like on account of their characteristic of speeding up electron transfer between
TMB and H 2 O 2 , and their enzymatic kinetics was in accordance with the typical
Michaelis–Menten theory. A highly responsive colorimetric system for detection of
glucose was produced, and the limit of detection was estimated as little as 0.28 μM.
The system was further applied for discovery of glucose in human blood serum and
was successfully demonstrated, which suggested its promising use as peroxidase
imitators in pharmaceuticals, clinical diagnosis and environmental chemistry. Li et al.
(2015) described the production of glutathione (GSH)-capped platinum nanoparticles
by dissolving different concentrations of GSH (1–300 mM) in 10 mM PBS buffer (pH
5.0), then mixed with 300 mM K 2 PtCl4 and incubated for 2 h at 25 °C. Then freshly
prepared dimethylamine borane (DMAB) aqueous solution was mixed to the above
mixture for a 12 h-reduction at 25 °C. The GSH-capped PtNPs displayed activity
as peroxidase imitator which ranged from 2.3 to 3.6 nm. The limit of detection was
as little as 0.25 nM by using GSH-Pt having mean diameter of 3.6 nm. GSH-Pt
was reiterated as a capable component for colorimetric detection of Hg
2+ in both
drinkable water and biological fluids.
Some bimetallic nanomaterials have also been described to display peroxidase
mimetic potentials. Li et al. (2016b) found that cysteine-rich metallothioneins (MTs)
could improve the peroxidase mimic activity of citrate-capped AuNPs coated with
traces of mercury (AuNPs-Hg). The AuNPs with mean size of 13 nm were fabricated
by the citrate reduction method using 1 mM HAuCl 4 solution as a precausor. The
AuNPs accumulated by the cysteine-rich metallothioneins (AuNP-Hg-MTs) successfully catalyzed H 2 O 2 -mediated oxidation of 2,2
-azino-bis(3-ethylbenzothiazoline6sulfonate) (ABTS). This led to a color change and subsequent absorbance at 416 nm
which linearly corresponded to the concentration of MTs in the 4.3–49 nM range,
and the limit of detection was 1.3 nM. Thus, the technique was effectively applied
to determine MTs in (spiked) human urine. Jiang et al. (2016) produced a new
immunochromatographic assay (ICA) with improved sensitivity for both quantitative and visual exposure of E. coli O157:H7. Sandwich-type immunoreactions
were carried out on the immunochromatographic assay, and platinum–gold bimetal
nanoparticles (Pt–Au NPs) were aggregated on the test area. The Pt–AuNPs was fabricated by ultrasonically dissolving Pluronic F127 (10 mg) into 1.0 ml of a solution
containing K 2 PtCl 4 (20 mM), HAuCl 4 (20 mM) and HCl (6 M), and using ascorbic
acid as reducing substance while further washed with bovine serum albumin. The
signal amplification was based on Pt–AuNPs having high peroxidase activity toward
3,3
,5,5
-tetramethylbenzidine, which produced characteristic-colored signals and