Accelerated Activity-Based Sensing by Fluorogenic Reporter Engineering Enables to Rapidly Determine Unstable Analyte.

Accurate detection of labile analytes through activity based fluorogenic sensing is meaningful but remains a challenge because of nonrapid reaction kinetic. Herein, we present a signaling reporter engineering strategy to accelerate azoreduction reaction by positively charged fluorophore promoted unstable anion recognition for rapidly sensing sodium dithionite (Na2S2O4), a kind of widespread used but harmful inorganic reducing agent. Its quick decomposition often impedes application reliability of traditional fluorogenic probes in real samples because of their slow responses. In this work, four azo-based probes with different charged fluorophores (positive, zwitterionic, neutral, and negative) were synthesized and compared. Among of them, with sequestration effect of positively charged anthocyanin fluorophore for dithionite anion via electrostatic attraction, the cationic probe Azo-Pos displayed ultrafast fluorogenic response (∼2 s) with the fastest response kinetic (kpos' = 0.373 s-1) that is better than other charged ones (kzwi' = 0.031 s-1, kneu' = 0.013 s-1, kneg' = 0.003 s-1). Azo-Pos was demonstrated to be capable to directly detect labile Na2S2O4 in food samples and visualize the presence of Na2S2O4 in living systems in a timely fashion. This new probe has potential as a robust tool to fluorescently monitor excessive food additives and biological invasion of harmful Na2S2O4. Moreover, our proposed accelerating strategy would be versatile to develop more activity-based sensing probes for quickly detecting other unstable analytes of interest.

Fluorescence monitoring of refluxed tyrosinase using endoplasmic reticulum-localized enzymatic activity-based sensing.

A tyrosinase-activatable fluorescent probe with endoplasmic reticulum targetability was developed for the first time. It can ratiometrically fluoresce and hence be used to monitor refluxed tyrosinase into the endoplasmic reticulum.

Enzyme-Responsive Fluorescent Labeling Strategy for In Vivo Imaging of Gut Bacteria.

Myrosinase (Myr), as a unique ß-thioglucosidase enzyme capable of converting natural and gut bacterial metabolite glucosinolates into bioactive agents, has recently attracted a great deal of attention because of its essential functions in exerting homeostasis dynamics and promoting human health. Such nutraceutical and biomedical significance demands unique and reliable strategies for specific identification of Myr enzymes of gut bacterial origin in living systems, whereas the dearth of methods for bacterial Myr detection and visualization remains a challenging concern. Herein, we present a series of unique molecular probes for specific identification and imaging of Myr-expressing gut bacterial strains. Typically, an artificial glucosinolate with an azide group in aglycone was synthesized and sequentially linked with the probe moieties of versatile channels through simple click conjugation. Upon gut bacterial enzymatic cleavage, the as-prepared probe molecules could be converted into reactive isothiocyanate forms, which can further act as reactive electrophiles for the covalent labeling of gut bacteria, thus realizing their localized fluorescent imaging within a wide range of wavelength channels in live bacterial strains and animal models. Overall, our proposed method presents a novel technology for selective gut bacterial Myr enzyme labeling in vitro and in vivo. We envision that such a rational probe design would serve as a promising solution for chemoprevention assessment, microflora metabolic mechanistic study, and gut bacterium-mediated physiopathological exploration.

CD109 identified in circulating proteomics mitigates postoperative recurrence in chronic rhinosinusitis with nasal polyps by suppressing TGF-ß1-induced epithelial-mesenchymal transition.

BACKGROUND: Chronic rhinosinusitis with nasal polyps (CRSwNP) is a common inflammatory disorder with a high rate of recurrence. This study aimed to explore biomarkers for identifying patients with recurrent CRSwNP (rCRSwNP). METHODS: We recruited two independent cohorts. In the discovery cohort, rCRSwNP patients and non-recurrent CRSwNP (non-rCRSwNP) patients were recruited, and the serum proteomic profile was characterized. The top 5 upregulated and downregulated proteins were confirmed in the validation cohort by ELISA, WB, and qRT-PCR, and their predictive values for postoperative recurrence were assessed. In vitro, human nasal epithelial cells (HNEpCs) were employed to assess the ability of candidate proteins to induce epithelial-mesenchymal transition (EMT). RESULTS: Serum proteomics identified 53 different proteins, including 30 increased and 23 decreased, between the rCRSwNP and non-rCRSwNP groups. ELISA results revealed that serum levels of CD163 and TGF-ß1 were elevated, CD109 and PRDX2 were decreased in the rCRSwNP group compared to the non-rCRSwNP group, and serum CD163, TGF-ß1, and CD109 levels were proved to be associated with the risk of postoperative recurrence. In addition, qRT-PCR and WB revealed that tissue CD163, TGF-ß1, and CD109 expressions in rCRSwNP patients were enhanced compared to those non-rCRSwNP patients. Kaplan-Meier analysis showed that increased CD163 and TGF-ß1 expression and decreased CD109 expression are associated with the risk of recurrence in CRSwNP patients. Receiver operating characteristic curves showed that TGF-ß1 and CD109 had superior diagnostic performances for rCRSwNP. In vitro experiments showed that TGF-ß1 promoted EMT in HNEpCs, and overexpression of CD109 reversed this effect. Functional recovery experiments confirmed that CD109 could attenuate EMT in HNEpCs by inhibiting the TGF-ß1/Smad signaling pathway, attenuating EMT in epithelial cells. CONCLUSION: Our data suggested that TGF-ß1 and CD109 might serve as promising predictors of rCRSwNP. The TGF-ß1/Smad pathway was implicated in fostering EMT in epithelial cells, particularly those exhibiting low expression of CD109. Consequently, the absence of CD109 expression in epithelial cells could be a potential mechanism underlying rCRSwNP.

Rational design of an iminocoumarin-based fluorescence probe for peroxynitrite with high signal-to-noise ratio.

As a high reactive oxygen species (ROS) and a reactive nitrogen species (RNS), peroxynitrite anion (ONOO- ) is widely present in organisms and plays influential roles in physiological and pathological processes. It is of great significance to develop effective fluorescent probes for imaging peroxynitrite variation in living systems. Herein we present a novel fluorescent probe TQC0 for monitoring ONOO- based on the iminocoumarin platform, and this probe was synthesized by the knoevenagel condensation between a dihydropyridine-salicylaldehyde derivative and 2-benzothiazole-acetonitrile, and subsequently masked with the boronate moiety. The obtained probe TQC0 exhibited a high signal-to-noise ratio (206-fold) and a quick 'turn-on' response (about 10 min) with great selectivity and sensitivity. Furthermore, the probe TQC0 was successfully applied for imaging ONOO- in living cells with low cytotoxicity.

Electrocatalytic hydrogenation of indigo by NiMoS: energy saving and conversion improving.

An NiMo alloy bonded with sulfur (NiMoS) exhibits enhanced surface affinity toward water and organic molecules, thereby enhancing electrocatalytic hydrogenation (ECH) reactions through synergistic effects. In industrial processes, indigo, an ancient dye employed in the denim industry, is typically chemically reduced using sodium dithionite. However, this process generates an excess of toxic sulfide, which heavily contaminates the environment. ECH is a sustainable alternative for indigo reduction due to its reduced reliance on chemicals and energy consumption. In this study, carbon-felt (CF)-supported NiMoS was synthesized in a two-step process. First, the NiMo alloy was electrodeposited onto the CF surface, followed by sulfidation in an oven at 600 °C. NiMoS exhibits a larger electrochemically active surface area and a smaller charge transfer resistance compared to pure Ni and NiMo. Furthermore, NiMoS demonstrates excellent thermodynamic and kinetic properties for water splitting in strong alkaline solutions (1.0 M KOH). Additionally, optimal reaction conditions for the ECH of indigo were explored. Under the conditions of a 1.0 M KOH hydroxide medium with 10% methanol (v/v), an indigo concentration of 5 g L-1, a reaction temperature of 70 °C, and a current density of 10 mA cm-2, NiMoS/CF achieved remarkable improvements in both conversion (99.2%) and Faraday efficiency (38.1%). The results of this experimental work offer valuable insights into the design and application of novel catalytic materials for the ECH of vat dyes, opening up new possibilities for sustainable and environmentally friendly processes in the dye industry.

Simultaneous detection of multiple influenza virus subtypes based on microbead-encoded microfluidic chip.

Influenza virus, existing many subtypes, causes a huge risk of people health and life. Different subtypes bring a huge challenge for detection and treatment, thus simultaneous detection of multiple influenza virus subtypes plays a key role in fight against this disease. In this work, three kinds of influenza virus subtypes are one-step detection based on microbead-encoded microfluidic chip. HIN1, H3N2 and H7N3 were simultaneously captured only by microbeads of different magnetism and sizes, and they were further treated by magnetic separation and enriched through the magnetism and size-dependent microfluidic structure. Different subtypes of influenza virus could be linearly encoded in different detection zones of microfluidic chip according to microbeads of magnetism and size differences. With the high-brightness quantum dots (QDs) as label, the enriched fluorescence detection signals were further read online from linearly encoded strips, obtaining high sensitivity with detection limit of HIN1, H3N2, H7N3 about 2.2 ng/mL, 3.4 ng/mL and 2.9 ng/mL. Moreover, a visual operation interface, microcontroller unit and two-way syringe pump were consisted of a miniaturized detection device, improving the detection process automation. And this assay showed strong specificity. This method improves a new way of multiple pathogens detection using microbead-encoded technologies in the microfluidic chip.

Magnetic-based Microfluidic Chip: A Powerful Tool for Pathogen Detection and Affinity Reagents Selection.

The global outbreak of pathogen diseases has brought a huge risk to human lives and social development. Rapid diagnosis is the key strategy to fight against pathogen diseases. Development of detection methods and discovery of related affinity reagents are important parts of pathogen diagnosis. Conventional detection methods and affinity reagents discovery have some problems including much reagent consumption and labor intensity. Magnetic-based microfluidic chip integrates the unique advantages of magnetism and microfluidic technology, improving a powerful tool for pathogen detection and their affinity reagent discovery. This review provides a summary about the summary of pathogen detection through magnetic-based microfluidic chip, which refers to the pathogen nucleic acid detection (including extraction, amplification and signal acquisition), pathogen proteins and antibodies detection. Meanwhile, affinity reagents are served as the critical tool to specially capture pathogens. New affinity reagents are discovered to further facilitate the pathogen diagnosis. Microfluidic technology has also emerged as a powerful tool for affinity reagents discovery. Thus, this review further introduced the selection progress of aptamer as next generation affinity through the magnetic-based microfluidic technology. Using this selection technology shows great potential to improve selection performance, including integration and highly efficient selection. Finally, an outlook is given on how this field will develop on the basis of ongoing pathogen challenges.

A universal construction of robust interface between 2D conductive polymer and cellulose for textile supercapacitor.

Conductive polymer (CP) fabric is considered as the ideal electrode for flexible energy storage due to its light weight, good flexibility and high energy storage properties. However, the conventional polymer-coated cellulose fiber synthesized by liquid-phase oxidation polymerization always forms disordered assembly of polymer particles on fiber, which endures poor mechanical stability. Here, we report a two-dimensional (2D) CP based fabric electrode realized by a salt-template assisted vapor-phase polymerization method, which achieves robust coating of 2D CP on various cellulose fibers. Typically, the prepared 2D polypyrrole@cotton electrode displays a high specific capacitance (902.6 mF cm-2) and good cycling stability (86.5% capacitance retention after 12,000 cycles). The capacitance of flexible symmetrical device retains at more than 90% when it is bent to 180° after 1000 bending cycles. This work provides a new strategy for the robust interface between functional materials and cellulose fibers, and has great potential for commercial mass production.

Facile construction of dual heterojunction CoO@TiO2/MXene hybrid with efficient and stable catalytic activity for phenol degradation with peroxymonosulfate under visible light irradiation.

Photocatalysis and peroxymonosulfate (PMS) based advanced oxidation processes (AOP) are emerging technology for the degradation of refractory organic pollutant in the field of water treatment. Here we report a novel CoO@TiO2/MXene (CTM) hybrid through a facile sonication-hydrothermal method for efficient degradation of phenol via an integrated PMS activation-photocatalysis process. Benefiting from the proper position and superior suitability of the band structure, a dual interfacial charge transport channel was constructed, boosting the separation of photo-generated charge carriers and generating sufficient potential difference for redox reaction. Accordingly, the CTM hybrid not only possessed the outstanding photocatalytic activity but also dramatically accelerated PMS activation to generate considerable reactive radicals. As a result, over 96% phenol degradation was achieved in the 10% CTM/PMS/Vis system within 15 min. The radical quenching test and EPR analysis reveal that SO4•-, O2•- and 1O2 were predominant reactive species involved in the catalytic process. Moreover, the damaged chemical structure of CoO during PMS activation could be healed by the photo-actuated Co(II) regeneration to allow for continuous and stable catalytic process. This study offers a promising perspective for the rational design of competent and stable hybrid heterojunction catalyst to construct PMS activation-photocatalysis processes for the efficient degradation of organic contaminants.

Bioreduction (AuIII to Au0) and stabilization of gold nanocatalyst using Kappa carrageenan for degradation of azo dyes.

Colloidal gold nanoparticles (AuNPs) have been used in high technology applications due to their optical and electronic properties. Unfortunately, these broader applications are severely hampered by their agglomeration tendency and instability. Therefore, in this study, highly stable and aggregation resistant AuNPs were synthesized using Kappa carrageenan (κ-car) media (as a reducing and stabilizing agent) by a green synthesis protocol. The effect of different factors of reaction such as the concentration of κ-car (Cκ-car %), reaction time (t), temperature (T), and solution pH (here after simply define to 'reaction parameters') was studied by one-variable-at-a-time technique to optimize the yield production of AuNPs. The characterization of AuNPs synthesized at optimum conditions revealed that the particles are spherical in shapes, smaller in size (13.5 ± 5.1 nm) with a narrow distribution, highly crystalline (d-spacing = 0.230 nm) in nature, well stabilized (zeta potential = -22.1 mV) by coating by a thin layer of κ-car carbohydrate. The synthesized AuNPs reveal excellent catalytic function in the degradation (up to 99%) of azo-dyes. The kinetics study in the degradation reaction revealed that the technique could be extended to real wastewater treatment applications.

Biomedical titanium alloys with Young's moduli close to that of cortical bone.

Biomedical titanium alloys with Young's moduli close to that of cortical bone, i.e., low Young's modulus titanium alloys, are receiving extensive attentions because of their potential in preventing stress shielding, which usually leads to bone resorption and poor bone remodeling, when implants made of their alloys are used. They are generally ß-type titanium alloys composed of non-toxic and allergy-free elements such as Ti-29Nb-13Ta-4.6Zr referred to as TNTZ, which is highly expected to be used as a biomaterial for implants replacing failed hard tissue. Furthermore, to satisfy the demands from both patients and surgeons, i.e., a low Young's modulus of the whole implant and a high Young's modulus of the deformed part of implant, titanium alloys with changeable Young's modulus, which are also ß-type titanium alloys, for instance Ti-12Cr, have been developed. In this review article, by focusing on TNTZ and Ti-12Cr, the biological and mechanical properties of the titanium alloys with low Young's modulus and changeable Young's modulus are described. In addition, the titanium alloys with shape memory and superelastic properties were briefly addressed. Surface modifications for tailoring the biological and anti-wear/corrosion performances of the alloys have also been briefly introduced.

Fabrication of low-cost beta-type Ti-Mn alloys for biomedical applications by metal injection molding process and their mechanical properties.

Titanium and its alloys are suitable for biomedical applications owing to their good mechanical properties and biocompatibility. Beta-type Ti-Mn alloys (8-17 mass% Mn) were fabricated by metal injection molding (MIM) as a potential low cost material for use in biomedical applications. The microstructures and mechanical properties of the alloys were evaluated. For up to 13 mass% Mn, the tensile strength (1162-938MPa) and hardness (308-294HV) of the MIM fabricated alloys are comparable to those of Ti-Mn alloys fabricated by cold crucible levitation melting. Ti-9Mn exhibits the best balance of ultimate tensile strength (1046MPa) and elongation (4.7%) among the tested alloys, and has a Young's modulus of 89GPa. The observed low elongation of the alloys is attributed to the combined effects of high oxygen content, with the presence of interconnected pores and titanium carbides, the formation of which is due to carbon pickup during the debinding process. The elongation and tensile strength of the alloys decrease with increasing Mn content. The Ti-Mn alloys show good compressive properties, with Ti-17Mn showing a compressive 0.2% proof stress of 1034MPa, and a compressive strain of 50%.

Microstructural evolution and mechanical properties of biomedical Co-Cr-Mo alloy subjected to high-pressure torsion.

The effects of severe plastic deformation through high-pressure torsion (HPT) on the microstructure and tensile properties of a biomedical Co-Cr-Mo (CCM) alloy were investigated. The microstructure was examined as a function of torsional rotation number, N and equivalent strain, εeq in the HPT processing. Electron backscatter diffraction analysis (EBSD) shows that a strain-induced martensitic transformation occurs by the HPT processing. Grain diameter decreases with increasing εeq, and the HPT-processed alloy (CCMHPT) for εeq=45 exhibits an average grain diameter of 47nm, compared to 70µm for the CCM alloy before HPT processing. Blurred and wavy grain boundaries with low-angle of misorientation in the CCMHPT sample for εeq<45 become better-defined grain boundaries with high-angle of misorientation after HPT processing for εeq=45. Kernel average misorientation (KAM) maps from EBSD indicate that KAM inside grains increases with εeq for εeq<45, and then decreases for εeq=45. The volume fraction of the ε (hcp) phase in the CCMHPT samples slightly increases at εeq=9, and decreases at εeq=45. In addition, the strength of the CCMHPT samples increases at εeq=9, and then decrease at εeq=45. The decrease in the strength is attributed to the decrease in the volume fraction of ε phase, annihilation of dislocations, and decrease in strain in the CCMHPT sample processed at εeq=45 by HPT.

Biosynthesised palladium nanoparticles using Eucommia ulmoides bark aqueous extract and their catalytic activity.

Palladium nanoparticles (PdNPs) are of great importance as catalytic materials. Their synthesis has been widely studied and interest in their properties is growing. Bio-based methods might be a greener option for designing the PdNPs with reduced environmental impacts. This study reports the synthesis of PdNPs by utilising the aqueous extract of medicinally important Eucommia ulmoides (E. Ulmoides) bark which functions as both reducing and capping agent in moderate reaction conditions. Reduction potential of E. Ulmoides bark aqueous extract was about -0.08 V vs. saturated calomel electrode by open-circuit voltage method and the rich polyphenolics was confirmed by cyclic voltammetry, which helps to reduce palladium ions to PdNPs. The characterisation through high-resolution transmission electron microscopic, energy dispersive X-ray spectroscopy and X-ray diffraction infer that the as-synthesised PdNPs were spherical in shape with a face cubic crystal structure. The results from dynamic light scattering suggest the PdNPs have the narrow size distribution with an average size of 12.6 nm. The lower zeta potential (-25.3 mV) and the Fourier transform infrared spectra indicate that the as-synthesised PdNPs keep remarkably stable for a long period due to the capped biomolecules on the nanoparticle surface. This method for synthesis of PdNPs is simple, economic, non-toxic and efficient. The PdNPs show excellent catalytic activity for the electro-catalytic oxidation of hydrazine and the catalytic reducing degradation of p-aminoazobenzene, a model compound of azo-dyes.

Microstructures, mechanical properties and cytotoxicity of low cost beta Ti-Mn alloys for biomedical applications.

The microstructures, mechanical properties and biocompatibility of low cost ß-type Ti-(6-18)Mn alloys were investigated after solution treatment. Ti-9 Mn exhibits the best combination of tensile strength and elongation among the fabricated alloys, and its performance is comparable to or superior to those of Ti-6Al-4V ELI (Ti-64 ELI) in terms of every parameter evaluated. A hardness of 338 HV, a Young's modulus of 94 GPa, a 0.2% proof stress of 1023 MPa, an ultimate tensile strength of 1048 MPa and elongation of 19% were obtained for Ti-9 Mn. Furthermore, the cell viability and metallic ion release ratios are comparable to those of commercially pure titanium, making this alloy promising for biomedical applications. The Young's modulus is also lower than that of Ti-64 ELI (110 GPa), which can possibly reduce the stress shielding effect in implanted patients. STATEMENT OF SIGNIFICANCE: This study evaluates mechanical and biological performance of low cost solution treated ß-type Ti-(6, 9, 13 and 18 mass%)Mn alloys. It includes alloys containing a Mn content range higher than most previously published works (which is around or lower than 8 mass%). Furthermore, the effects of the ω phase and the ß phase stability of the alloys over some mechanical properties and microstructures are discussed. Ion release behavior under simulated body fluids and cell viability are also evaluated. For the case of the Ti-9 Mn, a mechanical and biological performance that is comparable to or superior than that of the widely used Ti-6Al-4V ELI and commercially pure Ti was observed.

Wear transition of solid-solution-strengthened Ti-29Nb-13Ta-4.6Zr alloys by interstitial oxygen for biomedical applications.

In previous studies, it has been concluded that volume losses (V loss) of the Ti-29Nb-13Ta-4.6Zr (TNTZ) discs and balls are larger than those of the respective Ti-6Al-4V extra-low interstitial (Ti64) discs and balls, both in air and Ringer's solution. These results are related to severe subsurface deformation of TNTZ, which is caused by the lower resistance to plastic shearing of TNTZ than that of Ti64. Therefore, it is necessary to further increase the wear resistance of TNTZ to satisfy the requirements as a biomedical implant. From this viewpoint, interstitial oxygen was added to TNTZ to improve the plastic shear resistance via solid-solution strengthening. Thus, the wear behaviors of combinations comprised of a new titanium alloy, TNTZ with high oxygen content of 0.89 mass% (89O) and a conventional titanium alloy, Ti64 were investigated in air and Ringer's solution for biomedical implant applications. The worn surfaces, wear debris, and subsurface damage were analyzed using a scanning electron microscopy and an electron probe microanalysis. V loss of the 89O discs and balls are smaller than those of the respective TNTZ discs and balls in both air and Ringer's solution. It can be concluded that the solid-solution strengthening by oxygen effectively improves the wear resistance for TNTZ materials. However, the 89O disc/ball combination still exhibits higher V loss than the Ti64 disc/ball combination in both air and Ringer's solution. Moreover, V loss of the disc for the 89O disc/Ti64 ball combination significantly decreases in Ringer's solution compared to that in air. This decrease for the 89O disc/Ti64 ball combination in Ringer's solution can be explained by the transition in the wear mechanism from severe delamination wear to abrasive wear.

ß-Type titanium alloys for spinal fixation surgery with high Young's modulus variability and good mechanical properties.

Along with a high strength, ductility, and work hardening rate, a variable Young's modulus is crucial for materials used as implant rods in spinal fixation surgery. The potential in this context of Ti-(9,8,7)Cr-0.2O (mass%) alloys is reported herein. The microstructural and mechanical properties of the alloys were systematically examined as a function of their chromium content, and the ion release of the optimized alloy was investigated to assess its suitability as an implant material. In terms of the deformation-induced ω-phase transformation required for a variable Young's modulus, the balance between ß-phase stability and athermal ω-phase content is most favorable in the Ti-9Cr-0.2O alloy. In addition, this composition affords a high tensile strength (>1000MPa), elongation at break (∼20%), and work hardening rate to solution-treated (ST) samples. These excellent properties are attributed to the combined effects of deformation-induced ω-phase transformation, deformation twinning, and dislocation gliding. Furthermore, the ST Ti-9Cr-0.2O alloy proves resistant to metal ion release in simulated body fluid. This combination of a good biocompatibility, variable Young's modulus and a high strength, ductility, and work hardening rate is ideal for spinal fixation applications. STATEMENT OF SIGNIFICANCE: Extensive efforts have been devoted over the past decades to developing ß-type titanium alloys with low Young's moduli for biomedical applications. In spinal fixation surgery however, along with excellent mechanical properties, the spinal-support materials should possess high Young's modulus for showing small springback during surgery to facilitate manipulation but low Young's modulus close to bone once implanted to avoid stress shielding. None of currently used metallic biomaterials can satisfy these abovementioned requirements. In the present study, we have developed a novel alloy, Ti-9Cr-0.2O. Remarkably variable Young's modulus and excellent mechanical properties can be achieved in this alloy via phase transformations and complex deformation mechanisms, which makes the Ti-9Cr-0.2O preferred material for spinal fixation surgery.

Controllable biosynthesis of gold nanoparticles from a Eucommia ulmoides bark aqueous extract.

The present work reports the green synthesis of gold nanoparticles (AuNPs) by water extract of Eucommia ulmoides (E. ulmoides) bark. The effects of various parameters such as the concentration of reactants, pH of the reaction mixture, temperature and the time of incubation were explored to the controlled formation of gold nanoparticles. The characterization through high resolution-transmission electron microscopic (HRTEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) infer that the as-synthesized AuNPs were spherical in shape with a face cubic crystal (FCC) structure. The results from zeta potential and dynamic light scattering (DLS) suggest the good stability and narrow size distribution of the AuNPs. This method for synthesis of AuNPs is simple, economic, nontoxic and efficient. The as-synthesized AuNPs show excellent catalytic activity for the catalytic reducing decoloration of model compounds of azo-dye: reactive yellow 179 and Congo red.