Biosynthesis Of AuNPs Research Articles

Biosynthesis of Gold Nanoparticles (AuNPs) by Diopatra claparedii Grube, 1878 (Polychaeta: Onuphidae) and Its Antibacterial Activity

Gold nanoparticles (AuNPs) have gained attention as it possesses outstanding physicochemical properties, and utilised in variety of applications especially in biomedical and pharmaceutical. Majorly, AuNPs are produced by conventional methods (chemical and physical). However, these methods bring several drawbacks such as toxic, hazardous, low yield and non-environmental friendly. Hence, biosynthesis of AuNPs that compliance with ‘greener’ approach becomes vitals. In this study, marine tube worm of Diopatra claparedii (polychaetes) was employed as reducing agent in the biosynthesis of AuNPs. The biosynthesised of AuNPs by D. claparedii extract was successfully prepared under ambient temperature and normal atmospheric conditions. The formation of AuNPS was confirmed by the appearance of surface Plasmon resonance (SPR) bands around 540 to 560 nm characterized by UV-Vis spectroscopy. Scanning electron microscopy (SEM) showed that the AuNPs are mostly in agglomerated spherical like shapes with size ranging from 100 to 400 nm. Meanwhile, transmission electron microscopy (TEM) showed that the particles are in the size range from 25 to 60 nm, also mainly form in spherical like shape. The particle size of AuNPs in a range of 50-100 nm was showed by dynamic light scattering (DLS). Fourier-transform infrared (FTIR) spectrum of D. claparedii extract indicated the existence of several functional groups. Biosynthesised AuNPs also successfully gave inhibition on bacterial growth (Staphyloccus aureus, S. epidermidis, Escheratia coli, Salmonella typhi) through antibacterial assessment.

Bioengineered gold nanoparticles using Cynodon dactylon extract and its cytotoxicity and antibacterial activities.

In this study, simple and green route approach was applied for the synthesis gold nanoparticles (AuNPs) containing an aqueous extract of Cynodon dactylon L. Pers., (C. dactylon). The synthesized AuNPs were characterized using spectral and microscopic analysis. The changes in the color pattern were observed upon synthesis by UV-vis spectrophotometer with a peak of 530nm. The FT-IR, XRD, SEM, and TEM were used to analyze the crystal nature and morphology of the green synthesized AuNPs. The C. dactylon-loaded AuNPs in different concentrations (0.625-100μg/ml) were used to assess cytotoxicity activity against MCF-7 cell line and where the IC50 was found to be 31.34μg/ml by MTT assay. The C. dactylon-AuNPs were significantly increased reactive oxygen species (ROS) generation, DNA fragmentation, and mitochondrial membrane changes observed by dichlorodihydroflurescenin diacetate (DCFH-DA), 4',6-diamidino-2-phenylindole (DAPI), Rhodamine-123, and acridine orange (AO)/ethidium bromide (EtBr) staining assay. Besides the microbial study revealed that C. dactylon-AuNPs exhibited significant antibacterial activity against clinically isolated pathogenic bacteria such as Enterobacter cloacae, Staphylococus Haemolytics, Staphylococcus petrasii subsp. Pragensis and Bacillus cereus with a zone of inhibition 13, 12, 13 and 12mm, respectively. It could be concluded that C. dactylon has the ability to be involved in the biosynthesis of AuNPs, and the pharmacological studies proved the promising cytotoxic effect on MCF-7 cell line and pathogenic bacterial species.

Biosynthesis and characterization of gold nanoparticles using Brazilian red propolis and evaluation of its antimicrobial and anticancer activities

Gold nanoparticles (AuNPs) are highlighted due to their low toxicity, compatibility with the human body, high surface area to volume ratio, and surfaces that can be easily modified with ligands. Biosynthesis of AuNPs using plant extract is considered a simple, low-cost, and eco-friendly approach. Brazilian Red Propolis (BRP), a product of bees, exhibits anti-inflammatory, anti-tumor, antioxidant, and antimicrobial activities. Here, we described the biosynthesis of AuNPs using BRP extract (AuNPextract) and its fractions (AuNPhexane, AuNPdichloromethane, AuNPethyl acetate) and evaluated their structural properties and their potential against microorganisms and cancer cells. AuNPs showed a surface plasmon resonance (SPR) band at 535 nm. The sizes and morphologies were influenced by the BRP sample used in the reaction. FTIR and TGA revealed the involvement of bioactive compounds from BRP extract or its fractions in the synthesis and stabilization of AuNPs. AuNPdichloromethane and AuNPhexane exhibited antimicrobial activities against all strains tested, showing their efficacy as antimicrobial agents to treat infectious diseases. AuNPs showed dose-dependent cytotoxic activity both in T24 and PC-3 cells. AuNPdichloromethane and AuNPextract exhibited the highest in vitro cytotoxic effect. Also, the cytotoxicity of biogenic nanoparticles was induced by mechanisms associated with apoptosis. The results highlight a potential low-cost green method using Brazilian red propolis to synthesize AuNPs, which demonstrated significant biological properties.

Gold Nanoparticles Biosynthesized using Lignosus rhinocerotis Extracts: Comparative Evaluation of Biostatic and Cytotoxicity Effects

Gold nanoparticles (AuNPs) are a unique class of nanomaterials applied in biomedical applications. Biological synthesis or biosynthesis of AuNPs offers advantages including simple and cost-effective method as well as nontoxic to human, making it superior to chemical synthesis. In this study, comparative evaluation was conducted for antimicrobial and cytotoxicity effects of chemically synthesized (Chem-AuNPs) and biosynthesized AuNPs (Bio-AuNPs). Chem- and Bio-AuNPs were produced using sodium citrate and L. rhinocerotis extracts, respectively. Different methods namely hot and cold-water extraction (HWE and CWE, respectively) were used to extract L. rhinocerotis sclerotium, a medicinal mushroom. Both types of nanoparticles were stabilized using chitosan (CS) and characterized for their physical characteristics, followed by determination of antibacterial and cytotoxicity effects in vitro. Formation of AuNPs exhibited surface plasmon resonance (SPR) band at 465-564 nm and 523-544 nm for Chem-AuNPs and BioAuNPs, respectively, as determined by UV-vis spectroscopy. CS-stabilized AuNPs had larger size of particles than nonstabilized ones, ranging from 200 to 500 nm. Both Chem- and Bio-AuNPs showed biostatic activity against Grampositive bacteria (Bacillus sp. and Staphylococcus aureus) and Gram-negative bacteria (Pseudomonas aeruginosa and Escherichia coli). The cytotoxicity assay for 24 h showed higher cell viability for Bio-AuNPs than Chem-AuNPs, indicating relatively less toxicity of Bio-AuNPs. In conclusion, Bio-AuNPs using the mushroom extracts and CS provide opportunities for developing stable, safer, and eco-friendly nanoparticles with effective antibacterial properties for clinical applications.

Environmentally benign rapid biosynthesis of extracellular gold nanoparticles using Aspergillus flavus and their cytotoxic and catalytic activities

In this study, the rapid biosynthesis of gold nanoparticles (AuNPs) by Aspergillus flavus culture supernatant was achieved by reducing 1 mM of chloroauric acid (HAuCl4) within 2 min at pH 7 and 30 °C. The biosynthesized nanoparticles exhibited maximum absorbance at 545 nm in UVvis spectroscopy. Transmission electron microscopy exhibited that AuNPs tend to take nearly spherical shapes with an average size of 12 nm. Fourier transform infrared analysis indicated that carboxyl, amine, and hydroxyl groups may participate in the biosynthesis and stabilization of AuNPs. Its zeta potential was found to be -33.01 mV. Energy dispersive X-rays showed a strong and typical beak of gold nanocrystallites with 80.84 % of analyzed sample. X-Ray diffraction spectrum displayed Bragg reflections identical to the gold nanocrystals. The results confirmed that biosynthesized AuNPs are a potent anticancer agent against A549, HepG2 and MCF7 cell lines with IC50 value 53.5, 60.7 and 100 μg/mL, respectively. Crystal violet assay confirmed the cytopathic effects of AuNPs on HepG2 and A549 cell lines. Annexin-V FITC assay and cell cycle confirmed the apoptotic effect and cell cycle arrest in G2/M phase, respectively for A549 cell line. Moreover, the results showed a degradation efficiency of AuNPs to 4-nitrophenol within 16 min.

Biosynthesis of gold nanoparticles-peanut shell composite for catalytic reduction of methyl blue

Gold nanoparticles (AuNPs) has been recognized as an active and effective catalyst for many organic transformations. Currently, there is a growing need to develop AuNPs synthesis process that avoids the use of toxic chemicals or high energy requirement. In this research, the aqueous Phaleria macrocarpa (Mahkota dewa) dried fruit extract was used in the biosynthesis of AuNPs immobilized on peanut shell powder. The peanut shell supported AuNPs was characterized by UV–visible spectroscopy (UV–Vis), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetry analysis (TGA), Nitrogen (N2) adsorption-desorption and atomic absorption spectroscopy (AAS) techniques. The biosynthesized AuNPs was characterized by the appearance of a surface plasmon resonance (SPR) band at 534 nm in the UV–Vis spectrum. The XRD, TEM and TGA analytical data of AuNPs/Peanut shell composite indicated that the AuNPs with face-centred cubic (fcc) crystalline shape, mostly spherical and average particle size of 20.00 ± 4.19 nm were well dispersed on the peanut shell powder support. The FTIR analysis suggested that the C=O and O-H groups in the peanut shell powder have strong affinity to bind and stabilize the AuNPs. The BET surface area of the AuNPs/Peanut shell composite catalyst determined is 35.39 m² g-1 while the BJH pore volume is 0.035 cm3 g-1 with pore diameter of 2.07 nm. AAS elemental analytical data showed the Au loading is 0.03 mmol per gram of catalyst. The catalytic performance of the AuNPs/Peanut shell composite was investigated for the reduction of aqueous methyl blue (MB) at room temperature. The reduction of MB obeyed a pseudo-first-order reaction with the highest rate constant of 0.124 min-1. The supported AuNPs/Peanut shell composite catalyst could be easily recovered and reused for at least three times without significant loss of activity

Catalytic reduction of 4-nitrophenol over biostabilized gold nanoparticles supported onto thioctic acid functionalized silica-coated magnetite nanoparticles and optimization using response surface methodology

An environmentally benign magnetic gold nanoparticles (AuNPs) catalyst supported onto thioctic acid functionalized silica-coated magnetite nanoparticles, Au–RS–SR–NH–SiO2–Fe3O4,without employing any toxic reductant or capping agent was successfully synthesized. The Phaleria macrocarpa (Scheff.) Boerl (P. macrocarpa) fruit aqueous extract was used as the reducing and stabilizing agents for the biosynthesis of AuNPs. The catalytic performance of the magnetic AuNPs catalyst was evaluated for the reduction of 4-nitrophenol into 4-aminophenol in the presence of NaBH4. A three-factor Box–Behnken design coupled with response surface methodology was applied to evaluate the effects of several operating parameters, namely, volume of NaBH4, 4-nitrophenol concentration, and weight of Au–RS–SR–NH–SiO2–Fe3O4 on the conversion of 4-nitrophenol. The reduction of 4-nitrophenol using Au–RS–SR–NH–SiO2–Fe3O4 was welldescribed by a quadratic polynomial model. A significant quadratic model with p value ˂.0001 and R 2 = 0.9958 was achieved using the analysis of variance (ANOVA). The conversion of 4-nitrophenol to 4-aminophenol was maintained at 90% after five cycles.

One step preparation of stable gold nanoparticle using red cabbage extracts under UV light and its catalytic activity

Herein, we have reported the synthesis, characterization and catalytic activity of highly stable gold nanoparticles (Au NPs) using red cabbage extract (RCE) under UV irradiation. The anthocyanin groups predominantly existing in RCE play an essential role for biosynthesis of stable Au NPs. The reasons for using anthocyanins: 1) they act as chelating agents for preferentially reacting with gold ions (Au3+) to form Au3+- anthocyanin complexes, 2) as light-active reductants for reduction of Au3+ to zero valent Au0 under UV irradiation and 3) as stabilizing agent for preventing Au NPs from aggregation in high salt concentration owing to their unique salt tolerance property. We also demonstrate that how reaction time, concentration of RCE, pH value of reaction solutions and using one more reducing agent affected formation of the Au NPs. The stability of RCE Au NPs was comparatively studied with commercial (citrate stabilized) Au NPs against 100 mM salt (NaCl) solution. The RCE-Au NP showed reduction ability for conversion of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). UV–vis spectrometry, transmission electron microscopy (TEM), dynamic light scattering (DLS) and zeta potential (ZT) methods were utilized to characterize the Au NPs. We demonstrated that how whole RCE (anthocyanins molecules are major component) can be used as photo-active reducing and stabilizing agents to form Au NPs in a short time under UV irradiation and strong reducing agent without additional agents.

The pH role about synthesis, distribution and potential applications of gold nanoparticles

The synthesis of metallic nanoaprticles (NPs) is currently performed through the development of methodologies using microorganisms, plant extracts, and even organic waste, seeking to mitigate the impact on the environment. However, for both synthesis and biosynthesis it is necessary to consider physical and chemical factors such as temperature, stirring and pH, that allow controlling size and shape in an accurate way, as size and shape play an important role in the optical, electronic and thermal properties and determine many features of the structure and activity of molecules and biomolecules. In this work, we carry out chemical synthesis and biosynthesis of AuNPs at acidic (3-6), neutral (7) and basic (9) pH; the process is fast, simple and eco-friendly. We obtained AuNPs from 5-100 nm and determined that the pH of the solution is a key factor in the distribution and shape of the nanoparticles. Uniform AuNPs were obtained at neutral pH, or values of pH near neutrality. In addition, they have potential applications in various fields, due to their optical, magnetic, catalytic and electrical properties.

Process optimization for green synthesis of gold nanoparticles mediated by extract of Hygrophila spinosa T. Anders and their biological applications

Plant extract-mediated green synthesis of gold nanoparticles (AuNPs) and their biomedical application is currently gaining huge interest in the field of nanotechnology . In the present study, AuNPs were synthesized using Hygrophila spinosa aqueous extract (HSAE). The formation of AuNPs was confirmed by observing color change and characteristic absorbance peak for surface plasmon resonance by UV–Vis spectroscopy. Different reaction parameters such as HSAE concentration, salt concentration, pH, reaction time and temperature were optimized for biosynthesis of AuNPs. The NPs were characterized for particle size, surface morphology , crystallinity , elemental composition and surface functionalities. Cytotoxicity of the AuNPs was studied against different cancer cell lines by MTT assay and antioxidant potential as total antioxidant capacity was also evaluated. The biosynthesized AuNPs were small in size and negatively charged. Phytochemical screening of HSAE, and FTIR spectrum of synthesized AuNPs demonstrated participation of various groups of chemical compounds as capping and stabilizing agents in biosynthesis of AuNPs. The green synthesized AuNPs exhibited significantly higher anticancer activity compared to HSAE against breast, ovarian, glioblastoma/brain and multi-drug resistant ovarian cancer cell lines. Antioxidant activity of the synthesized AuNPs was less than HSAE. The biosynthesized AuNPs could be studied further to access their potency in the treatment and imaging of various cancers. • Green synthesis of AuNPs has been carried out with Hygrophila spinosa aqueous extract (HSAE). • Concentration of HAuCl 4 solution, pH, reaction incubation temperature & time, and concentration of HSAE have been optimized for synthesis of AuNPs. • Characterization by UV–Vis, FTIR, SEM, TEM, EDS and XRD confirm that HSAE could synthesize AuNPs. • Synthesized AuNPs exhibited promising antioxidant and anticancer activities.

Rod-shaped gold nanoparticles biosynthesized using Pb2+-induced fungus Aspergillus sp. WL-Au.

Gold nanoparticles (AuNPs) attracted much attention owing to their distinguished characteristics and applications. In this study, rod-shaped AuNPs were biosynthesized using Pb2+-induced fungus Aspergillus sp. The synthesized AuNPs showed a UV-vis absorption peak at 534nm. Scanning electron microscopy and transmission electron microscopy analyses showed that rod-shaped AuNPs were biosynthesized and attached on the mycelia surfaces. Energy-dispersive spectrometer analysis identified gold as the unique metallic composition of synthesized nanoparticles. X-ray powder diffraction analysis showed that the AuNPs were face-centered cubic crystalline structure. Furthermore, Fourier transform infrared spectroscopy analysis detected functional groups, including C = O, C-O-C, amine I and II which played active roles in AuNPs formation. In addition, the main shape of synthesized AuNPs changed from sphere to rod-shape with the increase of biomass and Pb2+ concentration. This study reports quite uniform rod-shaped AuNPs biosynthesized using Pb2+-induced fungus Aspergillus sp. WL-Au for the first time. This will provide a valid alternative for oriented biosynthesis of AuNPs.

Bio synthesis of colloidal AuNPs using thermally assisted pulse sonication method

The colloidal gold nanoparticles (AuNPs) were prepared using Aegle marmelos fruit peel extract (AMFPE) as a reducing agent followed by thermally assisted pulse sonication. The purple-red colour was observed due to the reduction of Au3+ ions to Au0. The AMFPE and thermally assisted pulse sonication enhance their catalytic and antioxidant activity. The thermally-assisted pulse sonicated biosynthesized colloidal AuNPs were characterized by UV–Vis spectrophotometer, Transmission Electron Microscopy (TEM), Selected-Area Electron Diffraction (SAED), X-ray Diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and Zeta potential. In this article SPR band was observed at 546 nm. TEM study shows the monodisperse and spherical shaped 25–30 nm sized nanoparticles. SAED and XRD patterns were confirmed FCC crystalline structure of colloidal AuNPs. FTIR study demonstrates the chemical bonds between the metal and AMFPE. Higher value of Zeta potential confirms the stability of the nanoparticles. The photo-catalytic activity of colloidal AuNPs was observed for catalysis of Methylene Blue (MB). Colloidal AuNPs shows significant antioxidant activity for DPPH (2,2-diphenyl-1-picrylhydrazyl) assay, total antioxidant assay (TAA), ferric reducing power assay (FRAP), nitric oxide and H2O2 (Hydrogen per oxide) scavenging activity. This is novel approach for bio synthesis of colloidal AuNPs using a thermally assisted pulse sonication method.

Green biosynthesis of gold nanoparticles by Lilium casa blanca petals and evaluation of catalytic activity

A simple, fast, and eco-friendly method for the biosynthesis of gold nanoparticles (AuNPs) using Lilium casa blanca petals as a reducing and protecting agent was reported. The heating time had been shortened to 30 min for biosynthesis of AuNPs, which only took 15 mg Lilium casa blanca petals powder. The biosynthetic AuNPs, which had a uniform particle size distribution, were in spherical with the average size of 5.933 ± 1.158 nm. In addition, the conversion rate of Au3+ to Au0 was quite high. Through the discussion on the nutrients' concentrations before and after the synthesis, it was found that sugars, alkaloids, flavonoids, and proteins were the reducing and stabilising agents. The biosynthetic AuNPs had good catalytic activity, taking the hydroboration of nitrophenol and methylene blue as examples. Catalytic reduction followed pseudo-first-order kinetics. Moreover, the apparent rate constant was a linear correlation with the concentrations of AuNPs. The normalised rate constant of the proposed AuNPs was higher than other reported AuNPs, which indicated the excellent catalytic activity. All the results foreshowed the wide range of applications of the biosynthetic AuNPs by Lilium casa blanca petals.

Biosynthesis and Potential Applications of Silver and Gold Nanoparticles and Their Chitosan-Based Nanocomposites in Nanomedicine

Biosynthesized or biogenic metallic nanoparticles, particularly silver and gold nanoparticles (AgNPs and AuNPs, respectively), have been increasingly used because of their advantages, including high stability and loading capacity; moreover, these nanoparticles are synthesized using a green and cost-effective method. Previous studies have investigated reducing and/or stabilizing agents from various biological sources, including plants, microorganisms, and marine-derived products, using either a one-pot or a multistep process at different conditions. In addition, extensive studies have been performed to determine the biological or pharmacological effects of these nanoparticles, such as antimicrobial, antitumor, anti-inflammatory, and antioxidant effects. In the recent years, chitosan, a natural cationic polysaccharide, has been increasingly investigated as a reducing and/or stabilizing agent in the synthesis of biogenic metallic nanoparticles with potential applications in nanomedicine. Here, we have reviewed the mechanism of biosynthesis and potential applications of AgNPs and AuNPs and their chitosan-mediated nanocomposites in nanomedicine.

Rapid mediated biosynthesis and quantification of AuNPs using persimmon (Diospyros Kaki L.f) fruit extract

Persimmon (Diospyros Kaki L.f), as a common fruit, is rich in polyphenols, flavonoids and sugars, having high ability for synthesis of nanoparticles. Thus, biosynthesis of AuNPs using persimmon fruit extract was investigated in this study. The results of UV–visible spectra, transmission electron microscopy images and dynamic light scattering demonstrated that the size and shape of AuNPs highly depended on the concentration of HAuCl4·4H2O and reaction temperature. When 1.0 and 1.5 mM of HAuCl4·4H2O were used as precursors, triangular and hexagonal AuNPs were formed; furthermore, 2.0 mM of HAuCl4·4H2O induced the formation of nanoaggregates. Although higher temperatures (e.g., 50, 60 and 70 °C) boosted the isotropic growth of AuNPs, they had no expressive impact on AuNPs size. Centrifugal ultrafiltration method with inductively coupled plasma-mass spectrometry was applied to assess the transformation efficiency of Au3+ during this biosynthesis procedure. So, the results indicated that more than 97% of Au3+ ions were successfully converted into AuNPs. In addition, the XRD analysis confirmed that AuNPs had face-centered cubic structure. Fourier transform infrared spectroscopy revealed that different functional groups (especially hydroxyl group) were mainly involved in the fabrication of AuNPs. The biosynthesized AuNPs exhibited good antioxidant and catalytic activities.

BIOSYNTHESIS OF GOLD NANOPARTICLES BY BACTERIA FROM HYPERALKALINE SPRING AND EVALUATION OF THEIR INHIBITORY ACTIVITY AGAINST PYOCYANIN PRODUCTION

Nanoparticles are used in wide range of applications given their unique optical, chemical and electronic properties. Microbial biosynthesis of nanoparticles has offered a milder and eco-friendly alternative to physical and chemical methods of synthesis. One potential use of nanoparticles is for the inhibition of quorum sensing-mediated processes by microorganisms during pathogenic colonization and infection. In this study, bacteria from hyperalkaline spring (pH 11) were isolated using various enrichment media. The isolates, phylogenetically related to Lysinibacillus sp. and Pseudomonas stutzeri, were investigated for their ability to biosynthesize gold nanoparticles (AuNPs) via reduction of chloroauric acid (HAuCl4) at pH 9. Extracellular synthesis of gold nanoparticles was confirmed by UV-Vis absorption analysis which showed a peak at 500-600 nm wavelength range corresponding to the surface plasmon resonance of AuNPs. The AuNPs synthesized were of spherical and irregular shapes as revealed by SEM analysis. The presence of elemental gold was further confirmed by EDX analysis. FTIR results showed that various functional groups are possibly involved in the reduction of HAuCl4 and stabilization of synthesized gold nanoparticles. The inhibitory effect of biosynthesized AuNPs was tested on the growth and pyocyanin production of Pseudomonas aeruginosa PA01 during a 72-hour incubation period. Although the biosynthesized AuNPs showed no toxicity to the test organism, an increasing inhibition level of pyocyanin production was observed with increasing volumes of nanoparticles used. The levels of pyocyanin in setups treated with biosynthesized gold nanoparticles at 10, 30 and 50 L were significantly lower compared to the untreated setups (P ≤ 0.05). Our findings demonstrate that bacteria adapted to alkaline conditions can be used for efficient biosynthesis of AuNPs, which exhibited potential biomedical application in inhibiting pyocyanin production.

Extracellular mycosynthesis of gold nanoparticles using Trichoderma hamatum : optimization, characterization and antimicrobial activity

Mycosynthesis of AuNPs by Trichoderma hamatum would provide some useful data for oriented biosynthesis of AuNPs. In addition, the applications of mycosynthesized AuNPs were studied against some pathogenic bacteria. Therefore, the gained results detect that these antimicrobial nanoparticles could be explored as hopeful candidates for a variety of biomedical and pharmaceutical applications. This study should provide a further prudence for the fungal-mediated synthesis of AuNPs.

Preparation gold nanoparticles using herb leaf extract for electro-oxidation determination of ascorbic acid

Green and efficient synthetic methods have been gaining great interest for the preparation of nanoparticles. In this contribution, the biosynthesis of gold nanoparticles (Au NPs) and its electro-oxidation activity for determination of ascorbic acid was studied. The biosynthesis of Au NPs was carried out using the Plectranthus amboinicus leaf extract as reducing agent and stabilizer. The optical property of biosynthesized Au NPs was determined by UV–Vis spectrophotometer. We further investigated the electro-catalytic property of the biosynthesized Au NPs by electro-oxidation of ascorbic acid.

Phytosynthesis of gold and silver nanoparticles enhance in vitro antioxidant and mitostimulatory activity of Aconitum toxicum Reichenb. rhizomes alcoholic extracts

Extracts obtained from different plant species proved to be a valuable tool in various biomedical applications. In the same time, the phytosynthesis of noble metal nanoparticles represents an already well-established route for obtaining nanoparticles with biological activity. The present paper studies the antioxidant activity and the cytogenetic effects of the alcoholic extracts from rhizomes of Aconitum toxicum Rchb., before and after the phytosynthesis of gold and silver nanoparticles, on the meristematic root cells of Allium cepa L., and on the general mitotic index and the progression rate through the mitotic phases, respectively, as well as on the genetic material organized in chromosomes. The extracts were characterized in terms of total polyphenolics content (1.49% and, respectively, 2.29%) and aconitine content (by HPLC – 4.891 mg/L and, respectively, 18.211 mg/L), while the phytosynthesis of metallic nanoparticles was monitored by UV–Vis spectrometry, X-ray diffraction, X-ray fluorescence and electron microscopy. Both the extracts and the obtained nanoparticles were evaluated for antioxidant potential (the antioxidant activity ranging between 78% and 84.32%) and cytogenetic effects. The obtained results prove the phytosynthesis of AgNPs and AuNPs with dimensions ranging from 9 nm to 15 nm for AuNPs, respectively from 53 nm to 67 nm for AgNPs. The extracts obtained from rhizomes of A. toxicum Rchb. induced mitotic stress, as well as a series of nuclear and mitotic aberrations. The biosynthesis of AgNPs and AuNPs intensified the antioxidant and mitostimulatory activity of the extracts.

Biosynthesis of Gold and Silver Nanoparticles Using Extracts of Callus Cultures of Pumpkin (Cucurbita maxima)

The potential of callus cultures and field-grown organs of pumpkin (Cucurbita maxima) for the biosynthesis of nanoparticles of the noble metals gold and silver has been investigated. Biosynthesis of AuNPs (gold nanoparticles) and AgNPs (silver nanoparticles) was obtained with flowers of C. maxima but not with pulp and seeds. With callus cultures established in MS-based medium the biogenesis of both AuNPs and AgNPs could be obtained. At 65 °C the biogenesis of AuNPs and AgNPs by callus extracts was enhanced. The AuNPs and AgNPs have been characterized by UV-visible spectroscopy, TEM, DLS and XRD. Well-dispersed nanoparticles, which exhibited a remarkable diversity in size and shape, could be visualized by TEM. Gold nanoparticles were found to be of various shapes, viz., rods, triangles, star-shaped particles, spheres, hexagons, bipyramids, discoid particles, nanotrapezoids, prisms, cuboids. Silver nanoparticles were also of diverse shapes, viz., discoid, spherical, elliptical, triangle-like, belt-like, rod-shaped forms and cuboids. EDX analysis indicated that the AuNPs and AgNPs had a high degree of purity. The surface charges of the generated AuNPs and AgNPs were highly negative as indicated by zeta potential measurements. The AuNPs and AgNPs exhibited remarkable stability in solution for more than four months. FTIR studies indicated that biomolecules in the callus extracts were associated with the biosynthesis and stabilisation of the nanoparticles. The synthesized AgNPs could catalyse degradation of methylene blue and exhibited anti-bacterial activity against E. coli DH5α. There is no earlier report of the biosynthesis of nanoparticles by this plant species. Callus cultures of Cucurbita maxima are effective alternative resources of biomass for synthesis of nanoparticles.