Dispersed AuNPs Research Articles

A peptide nucleic acid-regulated fluorescence resonance energy transfer DNA assay based on the use of carbon dots and gold nanoparticles.

A convenient fluorometric method was developed for specific determination of DNA based on peptide nuclei acid (PNA)-regulated fluorescence resonance energy transfer (FRET) between carbon dots (CDs) and gold nanoparticles (AuNPs). In this system, CDs that display lake blue fluorescence with excitation/emission maxima at 345/445nm were used as fluorometric reporter, while AuNPs were used as fluorescence nanoquencher. A neutral PNA probe, which is designed to recognize the target DNA, was used as a coagulant to control the dispersion and aggregation of AuNPs. Without DNA, PNA can induce immediate AuNP aggregation, thus leading to the recovery of the FRET-quenched fluorescence emission of CDs. However, the addition of the complementary target DNA can protect AuNPs from being aggregated due to the formation of DNA/PNA complexes, which subsequently produces a high fluorescence quenching efficiency of CDs by dispersed AuNPs. Under optimized conditions, quantitative evaluation of DNA was achieved in a linear range of 5-100nM with adetection limit of 0.21nM. This method exhibited an excellent specificity towards fully matched DNA. In addition, the application of this assay for sensitive determination of DNA in cell lysate demonstrates its potential for bioanalysis and biodetection. Graphical abstract A simple fluorometric biosensor for specific detection of DNA was developed based on peptide nuclei acid (PNA)-regulated fluorescence resonance energy transfer (FRET) between carbon dots (CDs) and gold nanoparticles (AuNPs).

Microwave method synthesis of magnetic ionic liquid/gold nanoparticles as ultrasensitive SERS substrates for trace clopidol detection.

Clopidol is one of the most widely used anti-coccidiosis drugs. Its residues in poultry products and the environment pose a serious threat to human health. In this work, microwave-assisted synthesis of magnetic ionic liquid/gold nanoparticles (MIL-Au NPs) as the SERS substrates were first designed for sensitive and reliable determination of clopidol residue in egg samples. The experiment shows that MIL(1-methyl-3-hexyl imidazole ferric tetrachloride ([C6mim]FeCl4)) and microwave play a key role in the dispersion and morphology of Au NPs. Under the optimal conditions, the as-prepared MIL-Au NPs were applied to the SERS detection of clopidol in methanol and egg solution and its detection limits can be as low as to 0.5μg/kg (equal to 0.5ppb) in both solutions. The standard curves with regression coefficients of 0.9298 and 0.93496 were constructed in the linear range of 100-1000ppb and 0.5-50ppb for clopidol in egg solutions. Moreover, satisfactory recoveries (97.5-103.2%) were obtained for egg samples. The developed SERS method provides a way for quantitation of clopidol and can be applied for the convenient, reliable, and highly sensitive detection of antibiotic residues in food and environment, which has great potential in food safety and biological monitoring. Graphical abstract.

Poly(vinyl) alcohol crosslinked composite packaging film containing gold nanoparticles on shelf life extension of banana

Abstract In this work, gold nanoparticles (AuNPs) and graphene oxide (GO) were successfully incorporated separately into the poly(vinyl) alcohol (PVA) crosslinked composite films. Glyoxal and/or glutaraldehyde (GA) were employed as a crosslinking agent in film fabrication. Through the analytical approach, the success in imparting the crosslink toward PVA by which the relative transmittance intensity of the hydroxyl group is subsided to a greater extent has verified by the FTIR analysis. The dispersion of AuNPs and GO in the PVA crosslinked composites have improved the mechanical or physical properties (tensile strength, Young’s modulus value, water vapor transmission rate, water solubility) and making them promising candidates for food packaging application. The outcome of the agar disk diffusion test reveals that AuNPs incorporated PVA crosslinked composite film possess a greater capability with the formation of the larger inhibition zone to prevent the microbial contamination than GO-PVA crosslinked composite film. Banana shelf life has qualitatively improved with PVA-glyoxal-AuNPs composite film for food preservation and affirmed the uses in food packaging applications.

Integrated dual-signal aptasensor based on magnet-driven operations and miniaturized analytical device for on-site analysis

A novel dual-signal sensing system was developed for on-site analysis. A custom-built miniaturized workstation coupled with a home-made magneto-electrochemical detection module was employed for electrochemical sensing. The miniaturized workstation could be controlled by smartphone and all devices and tools in this integrated dual-signal biosensing platform were portable, which applies to on-site analysis. Meanwhile, by simple separation, color responses could be captured by naked-eye observation to detect target even in the absence of any instrument. The differences in target amounts were converted into the color change of AuNPs dispersion and the current change on solid electrode. A particularly objective in developing such versatile dual-signal strategy is to offer an user-friendly, portable, time-saving and cost-effective analysis strategy. The feasibility of the naked-eye colorimetric/magneto-electrochemical biosensing strategy was exemplified by using ATP and Hg2+ as model target. The LOD of two targets in electrochemical unit were 5.203 pmol L−1 and 1.597 pmol L−1 (S/N = 3), respectively. More importantly, the versatile dual-signal platform possesses favorable extensibility and could realize on-demand fast screening of other targets by using appropriate aptamers.

Nonpolar Interface Composition in Cetyltrimethylammonium Bromide Reverse Micellar Environments to Control Size and Induce Anisotropy on Gold Nanoparticles

AbstractWe study the composition effect of non‐polar organic media in cetyltrimethylammonium bromide (CTAB) reverse micelles (RMs) on the interface properties and their use as nanoreactors for gold nanoparticles (AuNPs) synthesis. We evaluate how the molecular structure of aliphatic (n‐hexane) and aromatic (toluene) organic solvent influences the environments and interactions at the interface of n‐hexane/1‐butanol/CTAB and toluene/1‐butanol/CTAB RMs, as a key factor on AuNPs finals properties. Data show that the intermicellar exchange rate is affected by changing the organic solvent, and these facts influence AuNPs size, polydispersity, and morphology. FTIR and 1H NMR results suggest that in n‐hexane a rigid and compact micellar interface favors the formation of smaller AuNPs, while in toluene a more fluent micellar interface enhances the formation of larger and dispersed AuNPs. This specific interaction also affects the CTAB counterion (Br −) availability at the interface, which appears to be crucial to induce anisotropy of the AuNPs obtained.

Determination of adenosine triphosphate based on the use of fluorescent terbium(III) organic frameworks and aptamer modified gold nanoparticles.

A thiol-labeled adenosine triphosphate (ATP) binding aptamer is covalently linked on the surface of gold nanoparticles (AuNPs). This warrants protection of the red AuNPs from aggregation in high salt condition. The dispersed AuNPs can quench the fluorescence of the Tb(III)-MOFs at 547nm with the excitation wavelength of 290nm. This is ascribed to the combined action of inner filter effect, dynamic quenching and fluorescence resonance energy transfer. If the aptamer binds ATP to form folded structures, the AuNPs aggregate in high salt medium and the green fluorescence of the Tb(III)-MOFs is recovered. This method shows good sensitivity and selectivity for ATP, and the linear range is from 0.5 to 10μM of ATP with the detection limitat of 0.32μM. It was applied to the determination of ATP in (spiked) human plasma with satisfactory recoveries (from 93.2% to 106.3%). Oppositely, when the unlabeled aptamer is used instead of thiol-labeled aptamer in this process, the ATP-aptamer complexes rather than unlabeled aptamer provide greater protection for AuNPs against salt-induced aggregation. It is found that when the aptamer covalently binds to AuNPs, the steric hindrance is dominant for the stabilization of AuNPs; for unlabeled aptamer, the electrostatic repulsion is responsible for their stability, irrespective of whether ATP is present or not. These two different forces lead to the aggregation or dispersion of AuNPs with addition of target in salt solution. Graphical abstractThe impact of two repulsive forces (electrostatic repulsion and steric repulsion) on the stabilization of gold nanoparticles, and its application in fluorescent terbium metal-organic frameworks as a nanoprobe for adenosine triphosphate.

The dual-function of lipoic acid groups as surface anchors and sulfhydryl reactive sites on polymer-stabilized QDs and Au nanocolloids.

Coating inorganic nanocrystals [e.g., quantum dots (QDs) and gold nanoparticles] with polymer ligands presenting multiple lipoic acid anchoring groups provides nanocolloids with remarkable long-term colloidal and photophysical stability. Here, we show that the natural swelling of macromolecules leaves a fraction of the lipoic acid groups in the surface coating free, which are targeted for activation and conjugation to target molecules, using the reliable sulfhydryl-to-maleimide reaction. This implies that simple and efficient functionalization of the nanocrystals can be achieved without introducing additional reactive groups in the coating. We apply a photomediated ligand exchange strategy to luminescent QDs and AuNPs and react the resulting nanocrystals with maleimide Cy3 dye. We then use optical absorption and resonance energy transfer measurements applied to QD-Cy3 and AuNP-Cy3 conjugates to extract estimates for the fraction of accessible lipoic acid groups per QD or AuNP. In addition, we demonstrate the potential utility of this approach by constructing a ratiometric pH sensor made of QD-SNARF conjugates. Our ligand design combined with the photoligation strategy yield colloidally stable dispersions of QDs and AuNPs that present accessible reactive thiols, without introducing new functionalities or requiring disulfide reducing reagents, making them useful for potential use in applications such as biological sensing and imaging.

Highly Sensitive and Selective Colorimetric Detection of Creatinine Based on Synergistic Effect of PEG/Hg2+-AuNPs.

A colorimetric sensor, based on the synergistic coordination effect on a gold nanoparticle (AuNP) platform has been developed for the determination of creatinine. The sensor selects citrate stabilized AuNPs as a platform, polyethylene glycol (PEG) as a decorator, and Hg2+ as a linkage to form a colorimetric probe system (PEG/Hg2−–AuNPs). By forming hydrogen bond between the oxygen-containing functional groups of PEG and citrate ions on the surface of AuNPs, this probe shows good stability. PEG coordinated with Hg2+ synergistically and specifically on the surface of dispersed AuNPs, and the existence of creatinine could induce the aggregation of AuNPs with a corresponding color change and an obvious absorption peak shift within 5 min. This PEG/Hg2+–AuNPs probe towards creatinine shows high sensitivity, and a good linear relationship (R2 = 0.9948) was obtained between A620–522 nm and creatinine concentration, which can achieve the quantitative calculations of creatinine. The limit of detection (LOD) of this PEG/Hg2+–AuNPs probe was estimated to be 9.68 nM, lower than that of many other reported methods. Importantly, the sensitive probe can be successfully applied in a urine simulating fluid sample and a bovine serum sample. The unique synergistic coordination sensing mechanism applied in the designation of this probe further improves its high selectivity and specificity for the detection of creatinine. Thus, the proposed probe may give new inspirations for colorimetric detection of creatinine and other biomolecules.

Plasmonic Effects of Au Nanoparticles on the Vibrational Sum Frequency Spectrum of 4-Nitrothiophenol

Vibrational sum frequency spectra (vSFS) of 4-nitrothiophenol (4-NTP) have been utilized to study plasmonic effects arising from its interaction with gold nanoparticles (Au NPs). To this end three systems have been studied: 4-NTP adsorbed on deposited Au nanoparticles, a self-assembled monolayer of 4-NTP on flat Au with dispersed Au NPs atop and, as reference, a self-assembled monolayer of 4-NTP. For 4-NTP on 50 and 80 nm Au NPs an enhancement of the SF intensity due to plasmonic effects by less than 1 order of magnitude is inferred in comparison to the monolayer system after taking the particle density into account. The addition of Au NPs to the monolayer system on flat Au also selectively enhances the response to an in-plane field component of the 532 nm upconversion light.

Fluorescent aptasensor for carbendazim detection in aqueous samples based on gold nanoparticles quenching Rhodamine B.

This paper proposes a fluorescent aptasensor for the detection of carbendazim (CBZ) in aqueous solution using CBZ-specific aptamer as sensing probe, gold nanoparticles (AuNPs) and Rhodamine B (RhoB) as indicator, respectively. In the absence of CBZ, CBZ aptamer could wrap AuNPs and maintained it dispersed in NaCl solution basically. Contrarily, the aptamer could specifically combine with CBZ and form a stable aptamer-CBZ complex, leaving AuNPs exposed to be aggregated by NaCl solution. The dispersed AuNPs could efficiently quench the fluorescence of RhoB, but those aggregated AuNPs have poor capability to impair the fluorescent indicator. Thus, the concentration of CBZ could be detected quantitatively through the distinction of the fluorescence intensity. This convenient fluorescent assay for CBZ had a wide linear range from 2.33 to 800 nM and a 2.33 nM limit of detection (LOD). Furthermore, it had high selectivity over pesticides, antibiotics, metal ions and other disrupting chemicals. As for application, the method could determine CBZ in water samples with recoveries in the range of 96.3-111.2%. This fluorescent aptasensor possessed great potential application for CBZ detection in actual aquatic environment.

Single particle-based colorimetric assay of pyrophosphate ions and pyrophosphatase with dark-field microscope

We propose a sensitive colorimetric method for the detection of P2O74− and pyrophosphatase (PPase). Without Na4P2O7 and PPase, under the catalysis of gold nanoparticles (AuNPs), Cu(II) can be reduced to Cu by nicotinamide adenine dinucleotide (NADH), leading to the Cu-coating onto the surfaces of AuNPs, accompanied by the color change from green to red under the dark-field microscope observation. While in the presence of Na4P2O7, the formation of Au@Cu NPs is suppressed due to the strong complexation reaction between Cu(II) and Na4P2O7. Thus, the NPs exhibit uniform green color in the dark-field image. By quantitatively counting the integrated optical density (IOD) of red dots in the dark-field images, P2O74− concentration can be accurately determined. A linear logarithmic dependence on P2O74− concentrations from 0.1 nM to 10 mM with a limit of detection (LOD) of 0.0324 nM was obtained. The addition of PPase to the Na4P2O7-triggered dispersed AuNPs restores the formation of Au@Cu NPs owing to the hydrolysis of Na4P2O7 into sodium phosphate under the catalysis of PPase, resulting in reliable quantification of color change of NPs from red to green in the dark-field images. The LOD is as low as 0.0007 U/mL with a linear dynamic range of 0.005–10 U/mL.

Size-dependent elasticity of gold nanoparticle measured by atomic force microscope based nanoindentation

Elasticity is one of the key properties in gold nanoparticles (AuNPs) and plays an essential role in the process design and applications. In this work, we have proposed an Argon plasma based technique to obtain well dispersed and pure AuNPs without surface functional groups. Our investigation on the size-dependent elasticity focused on the AuNPs with the size ranging from 2 nm to 12 nm by using an atomic force microscope based nanoindentation technique under the peakforce quantitative nanomechanical mapping mode. The results show clearly that when the AuNPs are smaller than 6 nm, there is a significant increase in the elasticity as the smallest nanoparticles display a twofold higher elastic modulus of ∼140 GPa compared to bulk gold. Our result provides important experimental evidence that contributes to a better understanding of the size-property relations as well as process design in AuNPs, and it also can be applied to measure the mechanical properties in a wide range of nano-objects.

An Ultrasensitive Sensing of Carbaryl by Changing Catalytic Activity of AuNPs on Fehling Reaction-Resonance Scattering Spectroscopy

Acetylcholinesterase (AChE) can catalyze the hydrolysis of acetylthiocholine iodide (S-ACh-I) to produce thiocholine, which can crosslink with gold nanoparticles (AuNPs) by Au-S covalent bond and trigger AuNPs aggregation. The catalytic ability of aggregation of AuNPs is less than dispersed AuNPs. In the presence of carbaryl, which can inhibit the catalysis activity of AChE, therefore, the production amounts of thiocholine and aggregation degree were decreased. In the Fehling reaction, low aggregation degree AuNPs was used to catalyze the reduction of Cu2+ by glucose to form large size Cu2O particle. Large Cu2O particle has high resonance scattering signal intensities, which is negative correlated with carbaryl concentration. The developed assay was applied to detect the carbaryl in aqueous solutions, and two excellent linear relationships were obtained in the range of 0.03–3.31 nM and 26.50–265.05 nM. The limit of detection (LOD) of carbaryl was down to 17.49 pM. The proposed method was successfully used to determine the concentration of spiked carbaryl in the apple matrix, and satisfactory recovery and repeatability were obtained.

Novel potential and current type chiral amino acids biosensor based on L/D-handed double helix carbon nanotubes@polypyrrole@Au nanoparticles@L/D-cysteine

Novel chiral amino acids biosensor based on both potential difference and current ratio simultaneously was first established by employing left/right-handed double helix carbon nanotubes (L/D-DHCNT) with chiral structure as substrate material, and by self-assembly anchoring L/D-cysteine (L/D-Cys) on the surface of the left/right-handed double helix carbon nanotubes@Polypyrrole@Au nanoparticles nanocomposites (L/D-DHCNT@PPy@AuNPs). In this work, L/D-DHCNT@PPy@AuNPs@L/D-Cys was successfully constructed via a facile and environment-friendly process. Interestingly, in order to obtain highly dispersed AuNPs deposited on L/D-DHCNT, polypyrrole polymerized from pyrrole acts as a locating agent. Owing to the combination of unique performance of the L/D-Cys and L/D-DHCNT with chiral structure, and PPy and AuNPs with outstanding conductivity, an extremely efficient electrochemical chiral biosensing system was constructed that exhibited enhanced conductivity, sensitivity and chiral recognition capacity for tyrosine (Tyr), tryptophan (Trp) and glutamic acids (Glu) enantiomers. Utilizing both the potential difference and current ratio signal to commendably realize the electrochemical recognition and quantitative determination of amino acid enantiomers in their racemic solution. In addition, achieving the detection of Tyr in tablet samples by fabricated ultra-efficient electrochemical chiral biosensing system. Therefore, L/D-DHCNT@PPy@AuNPs@L/D-Cys as novel and ultrasensitive chiral biosensing system possesses the capability of chiral recognition of amino acid enantiomers, and it opens up the potential application of L/D-DHCNT@PPy@AuNPs@L/D-Cys in the field of chiral biosensors.

Fluorescent aptasensor for ofloxacin detection based on the aggregation of gold nanoparticles and its effect on quenching the fluorescence of Rhodamine B.

This paper proposes the idea of building a fluorescent biosensor for ofloxacin (OFL) determination in aqueous and milk samples by label-free OFL-specific aptamer, gold nanoparticles (AuNPs) and Rhodamine B (RB). In the absence of OFL, AuNPs are coated with OFL aptamer and maintain dispersed in the high concentration of NaCl. The dispersed AuNPs could reduce the strong fluorescence intensity of RB efficiently. By contrast, in the presence of OFL, OFL is combined with aptamer to form stable compounds, causing the aptamers separated from the surface of AuNPs, thus AuNPs would be exposed in the solution. And the aggregated AuNPs will not quench the fluorescence intensity of RB. Through the distinction of the fluorescence intensity, the concentration of OFL could be detected in aqueous and milk samples quantitatively. The convenient and specific fluorescent assay for OFL is established with a linear range (R = 0.9907) from 20 to 300 nM and a detection limit of 1.66 nM in aqueous solution, and a linear range (R = 0.9963) from 20 to 300 nM and a detection limit of 4.61 nM (1.66 μg/L) in milk samples. With the good sensitivity and selectivity, this biosensor has good application potential to detect OFL in food and environmental samples.

Emissions of terbium metal-organic frameworks modulated by dispersive/agglomerated gold nanoparticles for the construction of prostate-specific antigen biosensor.

Herein, a universal and multifunctional fluorescence sensor platform is designed by the interaction of aggregation/dispersion gold nanoparticles (AuNPs) with Tb-metal-organic frameworks (Tb-MOFs). It is found that the dispersed AuNPs rather than the aggregated ones can quench effectively the fluorescence of Tb-MOFs, and the quenching process presumably involves the mechanism of inner filter effect (IFE), dynamic quenching effect (DQE), and fluorescence resonance energy transfer (FRET). The different affinities of aptamer and aptamer-target complex toward AuNPs are employed to modulate the fluorescence signal change of Tb-MOFs. As the proof of concept, prostate-specific antigen (PSA), an efficient tumor indicator for prostate cancer, is selected as the target. At first, the PSA aptamer can protect AuNPs against salt-induced aggregation, leading to the fluorescence of Tb-MOFs quenching. Subsequently, upon PSA introduction, the rigid aptamer-PSA complex is formed and cannot stabilize AuNPs in high salt conditions, so the AuNPs aggregate significantly and the fluorescence of Tb-MOFs is restored. The linear range of PSA is achieved from 1 to 100ng/mL with a detection limit of 0.36ng/mL. Finally, this method has been validated to be sensitive and specific for PSA in human urine samples. Graphical abstract.

Hybrid nanocomposite curcumin-capped gold nanoparticle-reduced graphene oxide: Anti-oxidant potency and selective cancer cytotoxicity.

Nanotechnology-based antioxidants and therapeutic agents are believed to be the next generation tools to face the ever-increasing cancer mortality rates. Graphene stands as a preferred nano-therapeutic template, due to the advanced properties and cellular interaction mechanisms. Nevertheless, majority of graphene-based composites suffer from hindered development as efficient cancer therapeutics. Recent nano-toxicology reviews and recommendations emphasize on the preliminary synthetic stages as a crucial element in driving successful applications results. In this study, we present an integrated, green, one-pot hybridization of target-suited raw materials into curcumin-capped gold nanoparticle-conjugated reduced graphene oxide (CAG) nanocomposite, as a prominent anti-oxidant and anti-cancer agent. Distinct from previous studies, the beneficial attributes of curcumin are employed to their fullest extent, such that they perform dual roles of being a natural reducing agent and possessing antioxidant anti-cancer functional moiety. The proposed novel green synthesis approach secured an enhanced structure with dispersed homogenous AuNPs (15.62 ± 4.04 nm) anchored on reduced graphene oxide (rGO) sheets, as evidenced by transmission electron microscopy, surpassing other traditional chemical reductants. On the other hand, safe, non-toxic CAG elevates biological activity and supports biocompatibility. Free radical DPPH inhibition assay revealed CAG antioxidant potential with IC50 (324.1 ± 1.8%) value reduced by half compared to that of traditional citrate-rGO-AuNP nanocomposite (612.1 ± 10.1%), which confirms the amplified multi-potent antioxidant activity. Human colon cancer cell lines (HT-29 and SW-948) showed concentration- and time-dependent cytotoxicity for CAG, as determined by optical microscopy images and WST-8 assay, with relatively low IC50 values (~100 μg/ml), while preserving biocompatibility towards normal human colon (CCD-841) and liver cells (WRL-68), with high selectivity indices (≥ 2.0) at all tested time points. Collectively, our results demonstrate effective green synthesis of CAG nanocomposite, free of additional stabilizing agents, and its bioactivity as an antioxidant and selective anti-colon cancer agent.

Au/reduced graphene oxide composites: eco-friendly preparation method and catalytic applications for formic acid dehydrogenation

This paper presents a new, simple, accessible and environmentally friendly method to prepare gold-reduced graphene oxide composites (Au/rGO) with gold concentration of 2.5 wt%, 5 wt% and 10 wt%. The Au/rGO materials with low Au concentration present AuNPs of low dimensions and proved good catalytic activity for formic acid (FA) decomposition in aqueous solution. The most of the structural characteristics are not dependent of the gold content such as: large surface area (234–278 m2 g−1), good crystallinity of graphenes, few layers of carbon in the graphene support (5–6 layers), medium density of structural defects in graphene, the presence of remanent oxygenated groups on the graphene surface, very good dispersion of AuNPs on both sides of the graphene sheets. The AuNPs size instead is strongly dependent on the Au concentration: The smallest nanoparticles were obtained for Au2.5/rGO (3–5 nm) and the largest for Au10/rGO (10–14 nm). The position of the energy levels (conduction band and valence band) relative to the Fermi level also changes with the Au content.

Fabrication of 3-D confined spaces with Au NPs: Superior dispersion and catalytic activity

Gold nanoparticles (Au NPs) as an active noble-metal site have received great attention because of its superior catalytic activity in diverse reactions. However, the activity of Au NPs is strongly dependent on its size and dispersion degree. Therefore, we developed an efficient solid-state reduction (SSR) strategy for the first time to promote the dispersion degree and size of Au NPs in template-occluded KIT-6 (AK) as a support by taking advantage of (i) 3-dimentonal cubic mesoporous structure of support (ii) confined spaces present between template (Pluronic (P) 123) and silica wall of AK where Au NPs locate (iii) interaction of both P123 as template and silica walls of AK with Au NPs highly efficient for Au NPs dispersion and (iv) SSR strategy which avoids competitive adsorption of solvent in the conventional fabrication process. The results revealed that Au-based AK (AuAK) has much better dispersion of Au NPs with smaller sizes than template-free KIT-6 (CK). Moreover, the catalytic activity of AuAK in reduction reactions of p-nitrophenol (P-NP) to p-aminophenol (P-AP) and Methylene blue (MB) to Leuco MB (LMB) is superior than AuCK as well as to those Au-catalysts synthesized via conventional strategies previously. The catalytic performance is also related well with characterization results.

DNA-Templated In Situ Synthesis of Highly Dispersed AuNPs on Nitrogen-Doped Graphene for Real-Time Electrochemical Monitoring of Nitric Oxide Released from Live Cancer Cells.

Dispersion promotion of nanomaterials can significantly enhance their catalytic activities. With a new DNA-templated in situ synthesis approach, we report the preparation of highly dispersed AuNPs on nitrogen-doped graphene sheets (NGS) with significantly improved electrocatalytic ability for the monitoring of nitric oxide (NO) released from live cancer cells. The template DNA is adsorbed on NGS via π-π stacking, and the Au precursor chelates along the DNA lattice through dative bonding. Subsequent introduction of the reducing agent leads to in situ nucleation and growth of AuNPs, eventually resulting in highly dispersed AuNPs on NGS. Because of the synergistic enhancement of the catalytic activities of AuNPs and NGS, as well as the high dispersion of AuNPs, such a nanocomposite shows significant electro-oxidation capability toward NO, leading to a highly sensitive subnanomolar detection limit for NO in vitro. More importantly, the laminin glycoproteins can be readily adsorbed on the surface of the nanomaterials to render excellent biocompatibility for the adhesion and proliferation of live cells, enabling the biointerface for electrochemical detection of NO released from live cancer cells.