A domestic pressure cooker mediated, facile autoclaving method for the synthesis of silver nanoparticles.

As an alternative to an expensive hydrothermal reactor, in the current method a domestic pressure was used for the synthesis of silver nanoparticles (Ag NP) using tree gum, kondagogu as dual functional reductant and stabilizer by autoclaving. The formation of Ag NP was evaluated with colour transformation, UV-Visible spectroscopy (UV-Vis) and transmission electron microscopy. The formation of Ag NP by gum confirmed from the developed yellow coloration of the solution and the appearance of surface plasmon resonance peak at 408 nm in the UV-Vis. The produced NP were spherical, polydisperse, particle size ranged from 2.9-17.6 nm and the average particle size was 4.5 ± 3.1 nm. The developed method is useful for demonstration, gaining hands on experience and production of metal and metal oxide NP in resource limited small laboratories, rural colleges, startups etc.•Pressure cooker serves as an easily accessible, durable, inexpensive, electricity independent hydrothermal nanoparticle production vessel.•Autoclaving serves as a facile, ecofriendly, less energy consuming, one pot, green method with dual functional role of in situ nanoparticle synthesis and sterilization.•Production of intrinsically safe and sterile nanoparticles amenable for in vivo and in vitro biomedical applications.

Biogenic silver nanoparticles as an antibacterial agent against bacterial leaf blight causing rice phytopathogen Xanthomonas oryzae pv. oryzae.

Silver nanoparticles (Ag NP) were produced utilizing leaf extract of rice cultivar Taichung native-1. Various factors like leaf extract, silver nitrate concentrations, and duration of autoclaving were standardized during synthesis. Nanoparticles were analyzed with UV-visible absorption spectroscopy (UV-vis), dynamic light scattering, zeta potential, X-ray diffraction and transmission electron microscopy techniques. The synthesis was noted at 0.4% extract, 0.6 mM silver nitrate, 30 min of autoclaving and NP formation was confirmed from 424 nm peak in UV-vis. NP showed zeta potential of - 27 mV, face-centered cubic (fcc) crystal nature and sized around 16.5 ± 5.9 nm. Biogenic NP synthesized from susceptible rice variety were used as an antibacterial agent against phytopathogen Xanthomonas oryzae pv. oryzae (Xoo), the causative agent of bacterial leaf blight (BLB) disease in rice. Antibacterial effect of Ag NP was evaluated using in vitro assays and in vivo efficacy under greenhouse conditions. Results confirmed effective inhibition of Xoo growth and colony formation by Ag NP and found to be the more powerful antibacterial agent. Besides, Ag NP treatment (10 µg/mL) caused an enhancement in seedling vigor index. Pots treated with Ag NP (15 µg/mL) in vivo in greenhouse showed disease severity of 26.6% and disease decrease over control of 49.2%, at a much lower NP concentration than earlier reported studies. Thus, the current report implies using the leaf extract synthesized Ag NP to control and BLB disease management in field conditions.

Rice leaf extract synthesized silver nanoparticles: An in vitro fungicidal evaluation against Rhizoctonia solani, the causative agent of sheath blight disease in rice.

Silver nanoparticles (Ag NP) were synthesized using rice leaf extract and optimized synthetic conditions were found to be 0.4 % leaf extract, 0.6 mM AgNO3 and 30 min of autoclaving. Produced NP were characterized using UV-vis, DLS, zeta potential, XRD, TEM and FTIR. Ag NP formation was established from UV-vis spectra and NP showed zeta potential value of -27.4 mV. NP were spherical, polydisperse and average size was 16.5 ± 6.2 nm. Antifungal activity of Ag NP was assessed by poisoned food technique and resazurin broth dilution against mycelium and sclerotia of fungus R. solani, the causative agent of sheath blight disease in rice. Results confirmed effective hyphal growth inhibition and % growth inhibition was dose dependent (2.5-10 µg/mL). Ag NP showed enhanced mycelial inhibition (81.7-96.7 %) at 10 µg/mL. MIC values of Ag NP were in the range of 5-10 and 15-20 µg/mL towards fungal mycelium and sclerotia, respectively. Ag NP treatment (20 µg/mL) completely inhibited the disease incidence at 20 µg/mL. Ag NP treatment (10 µg/mL) caused 1.3 and 1.5 times enhancement in seedling vigor index. Hence, Ag NP can be utilized towards management and control of various fungal diseases of crops.

Multifaceted activities of plant gum synthesised platinum nanoparticles: catalytic, peroxidase, PCR enhancing and antioxidant activities.

A single pot, green method for platinum nanoparticles (Pt NP) production was devised with gum ghatti (Anogeissus latifolia). Analytical tools: ultraviolet-visible (UV-vis), dynamic light scattering, zeta potential, transmission electron microscope, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy were employed. Wide continuous UV-vis absorption and black solution colouration proved Pt NP formation. Face-centred cubic crystalline structure of NP was evidenced from XRD. NPs formed were nearly spherical with a mean particle size of 3 nm. NP demonstrated a myriad of properties including catalytic, peroxidase, polymerase chain reaction (PCR) enhancing and antioxidant activities. Catalytic action of NP was probed via NaBH4 reduction of arsenazo-III dye. NP displayed considerable peroxidase activity via catalysis of 3, 3', 5, 5'-tetramethylbenzidine oxidation by H2O2. NP showed exceptional stability towards varying pH (3-11), temperature (25-100°C), salt concentration (0-100 mM) and storage time duration (0-12 months). In comparison with horse radish peroxidase, its applicability as an artificial peroxidase is advantageous. NP caused a two-fold enhancement in PCR yield at 0.4 nM. Also showed significant 1', 1' diphenyl picryl-hydrazyle scavenging (80.1%) at 15 µg/mL. Author envisages that the biogenic Pt NP can be used in a range of biological and environmental applications.

Tree gum stabilised selenium nanoparticles: characterisation and antioxidant activity.

Selenium nanoparticles (Se NPs) were synthesised using sodium borohydride as a reductant and gum kondagogu as a stabiliser. Plant gum serves as a renewable, non-toxic, non-immunogenic, biopolymer based feedstock. Role of gum on synthesis and mean particle size was studied using ultraviolet-visible spectroscopy and dynamic light scattering. NP generation was visualised with orange red colouration and NPs exhibited a surface plasmon resonance peak at 250 nm. Formed NPs were amorphous, polydisperse and spherical. NPs showed a bimodal distribution, size varied from 44.4 to 200 nm and mean particle size was 105.6 nm. NP solution exhibited a zeta potential of -39.9 mV, confirming the superior stability. In comparison to ionic Se, the gum capped Se NPs exhibited superior 1, 1-diphenyl-2-picrylhydrazyle and 2, 2-azinobis-(3-ethylbenzthinzoline-6-sulphonic acid) radial scavenging activities of 73.2 and 92.2%, respectively, at 25 µg/ml. Antibacterial potential of NPs was checked with well diffusion assay. NPs exhibited growth inhibition activity against Gram-positive bacteria only. Bacillus subtilis and Micrococcus luteus showed respective inhibition zones of 6.3 and 8.6 mm at 12 µg. Thus, the present study demonstrates the applicability of tree gum stabilised Se NPs as a potent antioxidant nutrition supplement at a much lower dose, in comparison with ionic Se.

Bacteriogenic synthesis of selenium nanoparticles by Escherichia coli ATCC 35218 and its structural characterisation.

A biosynthetic method for the production of selenium nanoparticles under ambient temperature and pressure from sodium selenite was developed using Gram-negative bacterial strain Escherichia coli ATCC 35218. Bacteriogenic nanoparticles were methodologically characterized employing UV-vis, XRD, Raman spectroscopy, SEM, TEM, DLS and FTIR techniques. Generation of nanoparticles was visualized from the appearance of red colour in the selenite supplemented culture medium and broad absorption bands in the UV-vis. Biofabricated nanoparticles were spherical, polydisperse, ranged from 100-183 nm and the average particle size was about 155 nm. Based on selected-area electron diffraction, XRD patterns; and Raman spectroscopy the nanospheres were found to be amorphous. IR spectrum revealed the involvement of bacterial proteins in the reduction of selenite and stabilization of nanoparticles. Used bacterial strain demonstrated efficient selenite reduction capability which was evident from 89.2% of selenium removal within 72 h at a concentration of 1 mM. Observation noted in the current study highlight the importance of bacterial reduction in selenium nanoparticle generation which can be scaled up for commercial production. Also, the bacteriogenic, amorphous nanoparticles can also be used as nutritional supplements for humans since selenium nanoparticles of 5-200 nm are bioavailable and known to induce seleno enzymes involved in antioxidant defence.

Biomimetic synthesis of selenium nanoparticles by Pseudomonas aeruginosa ATCC 27853: An approach for conversion of selenite.

A facile and green method for the reduction of selenite was developed using a Gram-negative bacterial strain Pseudomonas aeruginosa, under aerobic conditions. During the process of bacterial conversion, the elemental selenium nanoparticles were produced. These nanoparticles were systematically characterized using various analytical techniques including UV-visible spectroscopy, XRD, Raman spectroscopy, SEM, DLS, TEM and FTIR spectroscopy techniques. The generation of selenium nanoparticles was confirmed from the appearance of red colour in the culture broth and broad absorption peaks in the UV-vis. The synthesized nanoparticles were spherical, polydisperse, ranged from 47 to 165 nm and the average particle size was about 95.9 nm. The selected-area electron diffraction, XRD patterns; and Raman spectroscopy established the amorphous nature of the fabricated nanoparticles. The IR data demonstrated the bacterial protein mediated selenite reduction and capping of the produced nanoparticles. The selenium removal was assessed at different selenite concentrations using ICP-OES and the results showed that the tested bacterial strain exhibited significant selenite reduction activity. The results demonstrate the possible application of P. aeruginosa for bioremediation of waters polluted with toxic and soluble selenite. Moreover, the potential metal reduction capability of the bacterial strain can function as green method for aerobic generation of selenium nanospheres.

Facile synthesis of palladium nanocatalyst using gum kondagogu (Cochlospermum gossypium): a natural biopolymer.

Palladium nanoparticles (Pd NPs) were synthesised by using gum kondagogu (GK), a non-toxic ecofriendly biopolymer. GK acted as both reducing and stabilising agent for the synthesis of Pd NPs. Various reaction parameters, such as concentration of gum, Pd chloride and reaction pH were standardised for the stable synthesis of GK reduced stabilised Pd NPs (GK-Pd NPs). The nanoparticles have been characterised using ultraviolet-visible spectroscopy, transmission electron microscopy and X-ray diffraction. Physical characterisation revealed that the gum synthesised Pd NPs were in the size range of 6.5 ± 2.3 nm and crystallised in face centred cubic (FCC) symmetry. Fourier transform infrared spectroscopy implicated the role of carboxyl, amine and hydroxyl groups in the synthesis. The synthesised Pd NPs were found to be highly stable in nature. The synthesised nanoparticles were found to function as an effective green catalyst (k = 0.182 min⁻¹) in the reduction of 4-nitrophenol by sodium borohydride, which was evident from the colour change of bright yellow (nitrophenolate; λ(max) - 400 nm) to colourless (4-AP; λ(max) - 294 nm) solution. The overall objectives of the current communication were: (i) to synthesize the Pd NPs using a green reducing/capping agent; GK and (ii) to determine the catalytic performance of the synthesised Pd NPs.

Antibacterial activity of biogenic silver nanoparticles synthesized with gum ghatti and gum olibanum: a comparative study.

Presently, silver nanoparticles produced by biological methods have received considerable significance owing to the natural abundance of renewable, cost-effective and biodegradable materials, thus implementing the green chemistry principles. Compared with the nanoparticles synthesized using chemical methods, most biogenic silver nanoparticles are protein capped, which imparts stability and biocompatibility, and enhanced antibacterial activity. In this study, we compared the antibacterial effect of two biogenic silver nanoparticles produced with natural plant gums: gum ghatti and gum olibanum against Gram-negative and Gram-positive bacteria. Bacterial interaction with nanoparticles was probed both in planktonic and biofilm modes of growth; employing solid agar and liquid broth assays for inhibition zone, antibiofilm activity, inhibition of growth kinetics, leakage of intracellular contents, membrane permeabilization and reactive oxygen species production. In addition, cytotoxicity of the biogenic nanoparticles was evaluated in HeLa cells, a human carcinoma cell line. Antibacterial activity and cytotoxicity of the silver nanoparticles synthesized with gum ghatti (Ag NP-GT) was greater than that produced with gum olibanum (Ag NP-OB). This could be attributed to the smaller size (5.7 nm), monodispersity and zeta potential of the Ag NP-GT. The study suggests that Ag NP-GT can be employed as a cytotoxic bactericidal agent, whereas Ag NP-OB (7.5 nm) as a biocompatible bactericidal agent.

Biosynthesis of silver nanoparticles by the seed extract of Strychnos potatorum: a natural phytocoagulant.

In this study, facile and ecofriendly methods have been developed for the biosynthesis of silver nanoparticles from silver nitrate using the seed extract of Strychnos potatorum, a natural phytocoagulant. The effect of room temperature stirring, water bath heating and autoclaving on nanoparticle synthesis was studied. The water soluble compounds in the extract serve as reducing and stabilising agents. Analytical techniques such as UV-visible spectroscopy, transmission electron microscopy (TEM) and X-ray diffraction were used to characterise the synthesised nanoparticles. By tuning the reaction conditions, size controlled spherical nanoparticles of around 14.1 ± 4.8 nm were generated. The face centred cubic crystalline structure of the nanoparticles is confirmed from the observed peaks corresponding to (111), (200), (220) and (311) planes in the XRD pattern, concentric rings with intermittent bright dots in selected-area electron diffraction patterns and clear lattice fringes in high-resolution TEM images. With Fourier transform infrared spectroscopy and Raman spectroscopy, a probable mechanism involved in the reduction and stabilisation of nanoparticles has been investigated. As the silver nanoparticles are encapsulated with functional groups, they can be easily integrated for various biomedical applications.

Enhancement of antibacterial activity of capped silver nanoparticles in combination with antibiotics, on model gram-negative and gram-positive bacteria.

The nanoparticles used in this study were prepared from AgNO3 using NaBH4 in the presence of capping agents such as citrate, sodium dodecyl sulfate, and polyvinylpyrrolidone. The formed nanoparticles were characterized with UV-Vis, TEM, and XRD. The generation of silver nanoparticles was confirmed from the appearance of yellow colour and an absorption maximum between 399 and 404 nm. The produced nanoparticles were found to be spherical in shape and polydisperse. For citrate, SDS, and PVP capped nanoparticles, the average particle sizes were 38.3 ± 13.5, 19.3 ± 6.0, and 16.0 ± 4.8 nm, respectively. The crystallinity of the nanoparticles in FCC structure is confirmed from the SAED and XRD patterns. Also, the combined antibacterial activity of these differently capped nanoparticles with selected antibiotics (streptomycin, ampicillin, and tetracycline) was evaluated on model Gram-negative and Gram-positive bacteria, employing disc diffusion assay. The activity of the tested antibiotics was enhanced in combination with all the stabilized nanoparticles, against both the Gram classes of bacteria. The combined effects of silver nanoparticles and antibiotics were more prominent with PVP capped nanoparticles as compared to citrate and SDS capped ones. The results of this study demonstrate potential therapeutic applications of silver nanoparticles in combination with antibiotics.

Size-controlled green synthesis of silver nanoparticles mediated by gum ghatti (Anogeissus latifolia) and its biological activity.

BACKGROUND: Gum ghatti is a proteinaceous edible, exudate tree gum of India and is also used in traditional medicine. A facile and ecofriendly green method has been developed for the synthesis of silver nanoparticles from silver nitrate using gum ghatti (Anogeissus latifolia) as a reducing and stabilizing agent. The influence of concentration of gum and reaction time on the synthesis of nanoparticles was studied. UV-visible spectroscopy, transmission electron microscopy and X-ray diffraction analytical techniques were used to characterize the synthesized nanoparticles. RESULTS: By optimizing the reaction conditions, we could achieve nearly monodispersed and size controlled spherical nanoparticles of around 5.7 ± 0.2 nm. A possible mechanism involved in the reduction and stabilization of nanoparticles has been investigated using Fourier transform infrared spectroscopy and Raman spectroscopy. CONCLUSIONS: The synthesized silver nanoparticles had significant antibacterial action on both the Gram classes of bacteria. As the silver nanoparticles are encapsulated with functional group rich gum, they can be easily integrated for various biological applications.

Highly stable, protein capped gold nanoparticles as effective drug delivery vehicles for amino-glycosidic antibiotics.

A method for the production of highly stable gold nanoparticles (Au NP) was optimized using sodium borohydride as reducing agent and bovine serum albumin as capping agent. The synthesized nanoparticles were characterized using UV-visible spectroscopy, transmission electron microscopy, X-ray diffraction (XRD) and dynamic light scattering techniques. The formation of gold nanoparticles was confirmed from the appearance of pink colour and an absorption maximum at 532 nm. These protein capped nanoparticles exhibited excellent stability towards pH modification and electrolyte addition. The produced nanoparticles were found to be spherical in shape, nearly monodispersed and with an average particle size of 7.8±1.7 nm. Crystalline nature of the nanoparticles in face centered cubic structure is confirmed from the selected-area electron diffraction and XRD patterns. The nanoparticles were functionalized with various amino-glycosidic antibiotics for utilizing them as drug delivery vehicles. Using Fourier transform infrared spectroscopy, the possible functional groups of antibiotics bound to the nanoparticle surface have been examined. These drug loaded nanoparticle solutions were tested for their antibacterial activity against Gram-negative and Gram-positive bacterial strains, by well diffusion assay. The antibiotic conjugated Au NP exhibited enhanced antibacterial activity, compared to pure antibiotic at the same concentration. Being protein capped and highly stable, these gold nanoparticles can act as effective carriers for drugs and might have considerable applications in the field of infection prevention and therapeutics.

Biofouling and microbial corrosion problem in the thermo-fluid heat exchanger and cooling water system of a nuclear test reactor.

This article discusses aspects of biofouling and corrosion in the thermo-fluid heat exchanger (TFHX) and in the cooling water system of a nuclear test reactor. During inspection, it was observed that >90% of the TFHX tube bundle was clogged with thick fouling deposits. Both X-ray diffraction and Mossbauer analyses of the fouling deposit demonstrated iron corrosion products. The exterior of the tubercle showed the presence of a calcium and magnesium carbonate mixture along with iron oxides. Raman spectroscopy analysis confirmed the presence of calcium carbonate scale in the calcite phase. The interior of the tubercle contained significant iron sulphide, magnetite and iron-oxy-hydroxide. A microbiological assay showed a considerable population of iron oxidizing bacteria and sulphate reducing bacteria (10(5) to 10(6) cfu g(-1) of deposit). As the temperature of the TFHX is in the range of 45-50 degrees C, the microbiota isolated/assayed from the fouling deposit are designated as thermo-tolerant bacteria. The mean corrosion rate of the CS coupons exposed online was approximately 2.0 mpy and the microbial counts of various corrosion causing bacteria were in the range 10(3) to 10(5) cfu ml(-1) in the cooling water and 10(6) to 10(8) cfu ml(-1) in the biofilm.