Peroxidase-like Activity Of AuNPs Research Articles

The peroxidase-like activity of Au NPs deposited inverse opal CeO2 nanozyme for rapid and sensitive H2O2 sensing

In this study, the hybrid nanozyme gold nanoparticles deposited CeO2 inverse opal photonic crystals (IOPCs) on the glass slide was fabricated by bestowing the hybrid with the beneficial porous morphology with its unique advantages: its surface valence states, high surface area, and copious active sites. The oxidase and peroxidase-mimicking activity was studied by observing the catalytic oxidation of chromogenic substrate 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) in the presence of H2O2, which can be visualized by the eyes. Au NPs and CeO2 IOPCs consisting of Ce3+ and Ce4+ can oxidize ABTS in the presence of H2O2 by mimicking peroxidase enzymes. The peroxidase-like activity of nanozyme was substantially improved by introducing light irradiation due to the photosensitive nature of the hybrid. The peroxidase-like activity of nanozyme enabled H2O2 linear detection over the range 9 to 500 μM, with a LOD of 2.7 µM. The acceptable nanozyme activity is probably owing to the easy access of H2O2 to the active sites of nanozyme. The porous architecture led to the easy channeling of reactants and products. The periodic architecture of the nanozyme also led to decent reproducibility. Without functionalization, the nanozyme can be a promising alternative to peroxidase enzymes for hydrogen peroxide measurements.

Robust Tag-Free Aptasensor for the Visual Determination of Lead Ion Based upon the Peroxidase-Catalytic Activity of Gold Nanoparticles

Here, a simple colorimetric strategy was developed to monitor lead ion (Pb2+) based upon the catalytic function of gold nanoparticles (AuNPs) regulated by the aptamer strands. The peroxidase-like activity of AuNPs was prevented by the aptamers through masking their surface. Thus, the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) did not proceed. By adding Pb2+, the aptamer-Pb2+ complex was formed that released the aptamer from the surface of AuNPs. Hence, free AuNPs initiated the oxidation of TMB that changed the solution color from colorless to blue. A linear concentration range was achieved from 0.2 to 200 nM with a detection limit (LOD) of 0.056 nM for Pb2+ detection. The aptasensor successfully monitored Pb2+ in drinking water, milk, and human serum. With the properties of sensitivity, simplicity, and naked-eye target monitoring, the developed aptamer-included biosensor (aptasensor) is suitable for food safety, health care application, and environmental monitoring.

Accelerating peroxidase-like activity of gold nanozymes using purine derivatives and its application for monitoring of occult blood in urine

Gold nanoparticles (AuNPs) is an important kind of nanozymes and a variety of its artificial enzymatic activities have been reported, such as oxidase, peroxidase, and superoxide dismutase. The DNA with poly purine-modified AuNPs shows an enhancement peroxidase activity compared with poly pyrimidine-modified AuNPs. In this work, purine derivatives are modified on the surface of AuNPs. The peroxidase-like activity of AuNPs is dependent on the chemical structure of the molecules capped on the surface. We find that ferric ions can accelerate the mimic enzymatic ability of 2, 6-diaminopurine (DAP) modified AuNPs. The enhanced catalytic activity comes from the synergistic reaction of AuNPs and ferric ions. The cooperative system can be applied to measure hemoglobin and red blood cells in urine with better sensitivity. Generally, there is no or few red blood cells in human urine. The presence of blood in the urine is closely related with serious diseases, for example chronic nephrotic syndrome and urinary system tumors. Compared the commercial urine test paper, the method based on DAP-AuNPs has a good sensitivity and wider quantitative range and will be helpful to do urine test at home.

Colorimetric sensor array for proteins discrimination based on the tunable peroxidase-like activity of AuNPs-DNA conjugates

We proposed a colorimetric sensor array for proteins discrimination based on the tunable catalytic activity of AuNPs-DNA conjugates. The peroxidase-like activity of AuNPs could be enhanced by the attachment of single-stranded oligonucleotides on its surface, resulting in highly sensitive colorimetric signal by catalyzing the oxidization of TMB. In the presence of different proteins, the AuNPs-DNA conjugates showed tunable catalytic activity, inducing differential colorimetric response. At the same time, the same protein could tune the catalytic activity of AuNPs decorated by different DNA with different degree. The fingerprint response generated from the sensor array was used for proteins discrimination. Compared to the colorimetric sensor array based on salt-induced AuNPs aggregation, this strategy exhibited much improved discrimination power for proteins at the low concentration. Seven proteins at the concentration of 10nM could be successfully identified and proteins spiked in human urine at the final concentration of 100nM could also be well distinguished. The discrimination accuracy of unknown samples was all 100% for these experiments. The current colorimetric array demonstrated its potential for highly sensitive diagnostic applications.

Aptamer based photometric assay for the antibiotic sulfadimethoxine based on the inhibition and reactivation of the peroxidase-like activity of gold nanoparticles

It is known that gold nanoparticles (AuNPs) possess peroxidase-like activity. They can catalyze the oxidation of 3,3,5,5-tetramethylbenzidine by H2O2 which leads to a color change from red to blue. It is shown here that the peroxidase-like activity of AuNPs can be inhibited by passivating its surface passivation with a ssDNA aptamer against sulfadimethoxine. If, however, the target molecule (sulfadimethoxine) is present, the aptamer is desorbed from the AuNPs surface, and this results in the reactivation of the catalytic property of the AuNPs. The color change of the solution (from purple to blue) is related to the analyte concentration, and this can be judged visually or by UV-visible absorptiometry at 650 nm. The assay, under optimized conditions, has a detection limit of 10 ng·mL−1 of sulfadimethoxine, and the calibration plot is linear over a rather wide concentration range (0.01–1000 μg·mL−1). The assay can be performed within <15 min, is sensitive, and therefore is well suited for fast screening in food analysis. Conceivably, it can be extended to many other small analytes for which aptamers are available.

Sensitive colorimetric detection of K(I) using catalytically active gold nanoparticles triggered signal amplification

In this work, we report a simple, ultrasensitive, and feasible colorimetric assay for metal ion (K+, used as a model) via inherent peroxidase-like enzymatic amplification strategy of gold nanoparticles (AuNPs). It is shown that peroxidase-like activity of AuNPs can be improved dramatically by its surface activation with target-specific aptamer molecules. Whereas when the target exists, the aptamers leave the surface of AuNPs in a target concentration-dependent manner, resulting in a decrease of the nanoenzymatic catalytic ability of AuNPs. Thus, K+ can be quantified in the presence of AuNPs by using a colorimetric sensing probe (3,3′,5,5′-tetramethylbenzidine). The color change of the solution is relevant to the dose of the target, and this can be achieved with the naked eyes and monitored by UV–vis spectrometry. A linear dependence between the absorbance and target K+ concentration is obtained under optimal conditions in the range from 0. 1nM to 1μM with a detection limit (LOD) of 0.06nM estimated at the 3Sblank level. The sensitivity displays to be 2–9 orders of magnitude better than those of other K+ detection methods. This sensing strategy may in principle be universally applicable for the detection of a range of environmental or biomedical molecules of interest.

Naked-eye sensitive ELISA-like assay based on gold-enhanced peroxidase-like immunogold activity.

A naked-eye sensitive ELISA-like assay was developed based on gold-enhanced peroxidase-like activity of gold nanoparticles (AuNPs). Using human IgG (H-IgG) as an analytical model, goat anti-human IgG antibody (anti-IgG) adsorbed on microtiter plate and AuNPs-labeled anti-IgG acted as capture antibody and detection antibody, respectively. Because the surfaces of AuNPs were blocked by protein molecules, the peroxidase-like activity of AuNPs was almost inhibited, evaluated by the catalytic oxidation of peroxidase enzyme substrate 3,3',5,5'-tetramethylbenzidine (TMB), which could produce a bright blue color in the presence of H2O2. Fortunately, the catalytic ability of AuNPs was dramatically increased by the deposition of gold due to the formation of a new gold shell on immunogold. Under optimal reaction conditions, the colorimetric immunoassay presented a good linear relationship in the range of 0.7-100 ng/mL and the limit of detection (LOD) of 0.3 ng/mL calculated by 3σ/S for UV-vis detection, and obtained LOD of 5 ng/mL for naked-eye detection. The obtained results were competitive with conventional sandwich ELISA with the LOD of 1.6 ng/mL. Furthermore, this developed colorimetric immunoassay was successfully applied to diluted human serum and fetal bovine serum samples, and predicted a broad prospect for the use of peroxidase-like activity involving nanomaterials in bioassay and diagnostics.

Visual detection of melamine based on the peroxidase-like activity enhancement of bare gold nanoparticles

In this study, a facile method to sensitively detect melamine and highly improve the peroxidase-like activity of bare gold nanoparticles (Au NPs) at the same time is proposed for the first time. It is interesting to find that the addition of melamine could improve the peroxidase-like activity of Au NPs. By coupling with 3,3′,5,5′-tetramethlybenzidine (TMB)–H2O2 chormogenic reaction, a novel method for colorimetic detection of melamine is developed. The detection limit of this method is as low as 0.2nM with the help of UV–vis spectroscopy and 0.5µM by naked-eye observation, both which are far below the US food and Drug Administration estimated melamine safety limit of 20µM. In addition, the present method is successfully applied for the detection of melamine in raw milk and milk powder. More importantly, the proposed method could also improve the peroxidase-like activity of Au NPs, which may not only provide a new approach to develop effective nanomaterials-based mimetic enzyme, but also irradiative to develop new applications for Au NPs in varieties of cost-effective and simple sensors in medicine, biotechnology and environmental chemistry.

Logic Control of Enzyme-Like Gold Nanoparticles for Selective Detection of Lead and Mercury Ions

Functional logic gates based on lead ions (Pb(2+)) and mercury ions (Hg(2+)) that induce peroxidase-like activities in gold nanoparticles (Au NPs) in the presence of platinum (Pt(4+)) and bismuth ions (Bi(3+)) are presented. The "AND" logic gate is constructed using Pt(4+)/Pb(2+) as the input and the peroxidase-like activity of the Au NPs as the output; this logic gate is denoted as "Pt(4+)/Pb(2+)(AND)-Au NPPOX". When Pt(4+) and Pb(2+) coexist, strong metallophilic interactions (between Pt and Pb atoms/ions) and aurophilic interactions (between Au and Pb/Pt atoms/ions) result in significant increases in the deposition of Pt and Pb atoms/ions onto the Au NPs, leading to enhanced peroxidase-like activity. The "INHIBIT" logic gate is fabricated by using Bi(3+) and Hg(2+) as the input and the peroxidase-like activity of the Au NPs as the output; this logic gate is denoted as "Bi(3+)/Hg(2+)(INHIBIT)-Au NPPOX". High peroxidase-like activity of Au NPs in the presence of Bi(3+) is a result of the various valence (oxidation) states of Bi(3+) and Au (Au(+)/Au(0)) atoms on the nanoparticle's surface. When Bi(3+) and Hg(2+) coexist, strong Hg-Au amalgamation results in a large decrease in the peroxidase-like activity of the Au NPs. These two probes (Pt(4+)/Pb(2+)(AND)-Au NPPOX and Bi(3+)/Hg(2+)(INHIBIT)-Au NPPOX) allow selective detection of Pb(2+) and Hg(2+) down to nanomolar quantities. The practicality of these two probes has been validated by analysis of Pb(2+) and Hg(2+) in environmental water samples (tap water, river water, and lake water). In addition, an integrated logic circuit based on the color change (formation of reddish resorufin product) and generation of O2 bubbles from these two probes has been constructed, allowing visual detection of Pb(2+) and Hg(2+) in aqueous solution.