Nanosilver-Promoted Lateral Root Development in Rice is Mediated through Hydrogen Peroxide

Nanosilver(10−9 m)refers to particles comprising 20–15,000 silver atoms,exhibiting high stability and specific surface area.At present,nanosilver has been used in agricultural cultivation and production.This study examined the effects of nanosilver on growth and development of rice root systems.Study results showed that fresh weight of rice belowground organs and root length both increased significantly by 5%and 25%,respectively,after rice radicles were treated with 2 ppm of nanosilver for three days.However,the H_(2)O_(2) level reached its peak at 2 days from treatment,but the activities of the antioxidant enzymes CAT,APX,and GR were inhibited by 2 ppm of nanosilver treatment.The results showed that nanosilver treatment inhibited the antioxidant enzyme activity of rice roots.The treatment of rice radicles with 5μM H_(2)O_(2) promoted root development and the same was observed when nanosilver was used for treatment.Moreover,ascorbic acid(AsA)is a H_(2)O_(2) scavenger and therefore rice root development was inhibited when AsA was added to rice radicles together with either treatment of nanosilver or H_(2)O_(2).In summary,nanosilver treatment of rice radicles promoted root growth and development via the regulation of H_(2)O_(2) and not the O2
−pathway.

Comparison of Photochemical and Thermal Degradation of Poly （Lactic Acid） Doped by Nanosilver

A comparison of thermal and photochemical degradation of poly （lactic acid） film materials （10/am） containing nanosilver are studied by FTlR （Fourier transform infrared） spectroscopy and DSC （differential scanning calorimetry）. Rates of thermal and photochemical degradation are determined by measuring the relative changes of absorbance （A/Ao） of selected bands in PLA （polylactic acid） spectra. Comparison of the effect of both degradation on PLA structure showed that nanosilver act as a stabilizer for photodegradation at 254 nm. As oppose, thermal degradation at 80 ~C indicate, that nanosilver accelerates PLA degradation at the temperature. Glass transition and crystallization/melting processes occurring in PLA and PLA/Ag nanocomposites during both degradation processes were also compared.

Development of African Earthenware Container Imbedded with Nanosilver Particles for Food Preservation

With the aim of ameliorating its preservation capacity, silver nanoparticles (0 - 100nm) with 99.9% purity and 35nm average particle size, were used as building material for earthenware jar, an extremely old container which is still used in rural African villages specifically in North Cameroon. Earth material was dissolved in water at the weight ratio of 5% to 10%. Silver nanoparticles were then added to the mixture and stirred to prepare 1% to 5% Ag/Earth paste (1 to 5 ppm). A grounded metal rotating drum was used to prepare earth embedded nanosilver plates. An n-order mathematic expression was used to evaluate the shelf-live quality and deterioration rate of sorghum porridge preserved in this African earthenware container imbedded with nanosilver particles. Accelerated shelf-life testing was used to predict the shelf life of the product at usual rural storage conditions. The used Arrhenius model indicated that the shelf life of the sorghum porridge stored in African earthenware container imbedded with nanosilver particles can be extended to 14 days at 4&degC ± 1&degC, 6 days at 15&degC ± 5&degC, and 4 days at 30&degC ± 2&degC. The calculated Q10 values were found to be in the range of 1.5 - 2.0.

Nanosilver alleviates foreign body reaction and facilitates wound repair by regulating macrophage polarization

Foreign body reactions induced by macrophages often cause delay or failure of wound healing in the application of tissue engineering scaffolds.This study explores the application of nanosilver(NAg)to reduce foreign body reactions during scaffold transplantation.An NAg hybrid collagen-chitosan scaffold(NAg-CCS)was prepared using the freeze-drying method.The NAg-CCS was implanted on the back of rats to evaluate the effects on foreign body reactions.Skin tissue samples were collected for histological and immunological evaluation at variable intervals.Miniature pigs were used to assess the effects of NAg on skin wound healing.The wounds were photographed,and tissue samples were collected for molecular biological analysis at different time points post-transplantation.NAg-CCS has a porous structure and the results showed that it could release NAg constantly for two weeks.The NAg-CCS group rarely developed a foreign body reaction,while the blank-CCS group showed granulomas or necrosis in the subcutaneous grafting experiment.Both matrix metalloproteinase-1(MMP-1)and tissue inhibitor of metalloproteinase-1(TIMP-1)were reduced significantly in the NAg-CCS group.The NAg-CCS group had higher interleukin(IL)-10 and lower IL-6 than the blank CCS group.In the wound healing study,M1 macrophage activation and inflammatory-related proteins inducible nitric oxide synthase(iNOS),IL-6,and interferon-(IFN-)were inhibited by NAg.In contrast,M2 macrophage activation and proinflammatory proteins(arginase-1),major histocompatibility complex-II(MHC-II),and found in inflammatory zone-1(FIZZ-1)were promoted,and this was responsible for suppressing the foreign body responses and accelerating wound healing.In conclusion,dermal scaffolds containing NAg suppressed the foreign body reaction by regulating macrophages and the expression of inflammatory cytokines,thereby promoting wound healing.

Promotion of reactive oxygen species activated by nanosilver surface engineering for resistant bacteria-infected skin tissue therapy

Nanosilver has been regarded as a promising alternative to traditional antibiotics for fighting pathogenassociated infections due to its efficacy toward a broad spectrum of pathogens.However,bacterial resistance to nanosilver has emerged recently.In this contribution,a surface engineering strategy based on N-halamine chemistry to address bacterial resistance to nanosilver was proposed.Using 1,3-dichloro-5,5-dimethylhydantoin(DCDMH)as an N-halamine source,AgCI nanodots were deposited on the surface of Ag nano wires(Ag NWs)via in situ redox reaction to prepare AgCl-on-Ag NWs.After in vitro and in vivo tests,AgCl-on-Ag NWs effectively inactivated two antibiotic-resistant bacteria,ampicillinresistant Escherichia coli(AREC)and methicillin-resistant Staphylococcus aureus(MRSA)with the minimum bactericidal concentration(MBC)as low as 10μg·ml~(-1)and exhibited good biosafety against normal cells.The experimental and theoretical tests demonstrated that AgCl-onAg NWs worked on AREC and MAS A by generating high level of reactive oxygen species under visible light irradiation,coupled with the sustained Ag ion release.Meanwhile,the antibacterial mechanism of AgCl-on-Ag NWs against MRSA was verified at the gene level by transcriptome analysis(RNA sequencing).Moreover,the fullthickness defect model verified that AgCl-on-Ag NWs reduced inflammatory cell infiltration and dramatically accelerated wound healing.This work provides a synergistic mechanism based on nanosilver surface engineering to eradicate the resistant bacteria that can alleviate drug resistance and develop an innovative approach for the treatment of bacterial infections.

A Sensitive Surface-enhanced Raman Scattering Method for Determination of Melamine with Aptamer-modified Nanosilver Probe

The small nanosilver was prepared by the sodium borohydride procedure. The aptamer was used to modify nanosilver to obtain a nanosilver-aptamer （AgssDNA） SERS probe for the determination of melamine. In pH 6.6 phosphate buffer solution and in the presence of NaCI, the AgssDNA probe specifically combined with melamine to release nanosilver particles that were aggregated to nanosilver clusters, which exhibited SERS effect at 240 cm-1. When melamine concentration increased, the nanosilver clusters increased, and the SERS intensity at 240 cm-1 in- creased. The increased SERS intensity AI240cm, is linear to melamine concentration in the range of 6.3--403.6 μg.L 1, with a detection limit of 1.2 μg L 1. This assay was applied to determination of melamine in milk, with sat- isfactory results. Keywords melamine, apatmer-modified nanosilver, aggregation, surface-enhanced Raman scattering

Nanosilver resonance scattering spectral method for determination of hydroxyl radical and its application

Silver nanoparticles were prepared under a microwave high-pressure condition using citric acid sodium as a reducer while the excess citrate was removed under high speed centrifugation. There is a resonance scattering (RS) peak at 470 nm for silver nanoparticles. In a pH 4.0 HAc-NaAc buffer solution, hydroxyl radicals from the Fenton reaction can oxidize silver nanoparticles to Ag+, resulting in the RS intensity decreasing. The decreased RS intensity at 470 nm (△I 470 nm) is linear with respect to the concentration of H2O2 (C) in the range of 0.27-7.56 μmol/L with a detection limit of 0.23 μmol/L. Its regression equation is △I 470 nm = 24.3 C + 13.8 with a correlation coefficient of 0.9959. This method was applied to screening the antioxidants with satisfactory results.

Tissue toxicity following the vaginal administration of nanosilver particles in rabbits

Nanosilver particles are used in various clinical settings because of their antibacterial properties.However,their safety evaluation when used for gynaecological disorders has not been established.Nanosilver particles were administrated in the vagina of New Zealand rabbits,and the pathological appearance of the surrounding tissue was examined by hematoxylin–eosin staining and transmission electron microscopy(TEM)after 1 and 3 days of treatment.The nanosilver content was assessed by plasma mass spectrometry,and the presence of particles in the hepatic portal vein blood was assessed by TEM.The results of our study show that the vaginal administration of nanosilver particles caused ultrastructural changes to the vaginal mucosa,urethra and rectum,with accumulation of particles in all tissues.These results demonstrate a new migration route of nanosilver particles following vaginal administration.They also demonstrate,for the first time,that the vaginal administration of nanosilver particles can enter the blood circulation system by examining the hepatic portal vein blood under the TEM which is the most direct visualized evidence.

Silver Nanoparticles in Cosmetics

This review is presented as a common interest in silver nanoparticles, their origin, activity, and toxicity in cosmetic. The application of nanotechnology and nanomaterials can be found in many cosmetic products including moisturizer, hair care products, makeup and sunscreen. Nanomaterials are now being used in leading cosmetics products, most commonly as chemicals used to give the protection. A silver nanoparticle is the potent and broad spectrum antimicrobial agent. This review paper looks into use of nano silver and provides an overview of current activity in this area.

Plasma ignition threshold disparity between silver nanoparticle-based target and bulk silver target at different laser wavelengths

Plasma ignition threshold of nanoparticle-based and bulk silver targets was measured in air. The plasma was initiated by a Nd:YAG laser at wavelengths of 355, 532, and 1064 nm. The plasma ignition was monitored utilizing the prominent Ag I line at 546.5 nm. Lower ignition thresholds of the nanoparticle-based silver target were estimated at 0.4?±?0.02, 0.34?±?0.04, and 0.27?±?0.035 J cm^(-2) coupled with the different laser wavelengths, respectively. In contrast, the bulk silver target plasma exhibited an order of magnitude higher ignition threshold. A three orders of magnitude enhanced emission intensity from the nano-based target over the bulk target was achieved at lower levels of laser irradiation. A reduction of the thermal diffusion length of the nanosilver was assumed in order to theoretically predict this reduction in the plasma threshold. In addition, the effect of self-reversal on the resonance lines was taken into consideration.

Characterization of Aluminum-Silver Nano Films and Its Effect as Antimicrobial and Degradation of Organic Compounds

Thin films were prepared from aluminum by spraying method with the addition of silver nanoparticles （50 nm） at different percentage （0, 25, 50, 75, 100%） for the preparation of nanocomposite A1-Ag film with thickness （0.1 μm） on a glass slide. The tests with XRD and SEM were done for prepared samples and then applied tests have been conducted to these thin films concerning to the biologicalactivity and the effect of light as well as degradationthe methylene blue dye and humus. The results showed that the addition of 50% of silver nanoparticles powder led to radical changes in the properties of the film, improving the biological activity as well as reducing high ratios addition. Thus it is possible, sufficient and appropriate to adopt this percentage for other bio- applications. The biological applications indicated the ability of this nanofilm to be applied as antimicrobial agent against the enterobacteriaceae family especially Escherichia coli, Klebsiella spp. and Proteus spp. under natural conditions and enhancing activity against Pseudomonas aeruginosa and Candida albicanes in presence of the light. It also founded the photoanalysis ability of this film toward the polycyclic compounds.

Brief Review of Silver Sinter-bonding Processing for Packaging High-temperature Power Devices

Silver sintering is receiving increasing attention due to its novel die-attach technique for high-temperature power electronics.Excellent thermal conductivity,high melting point/remelting temperature and low-temperature sintering behaviors of the silver sintered attachment meet the requirements of high-temperature applications for power devices,specifically SiC devices.The merits and demerits of the existing pressure-assisted sintering and pressure-less sintering techniques using nano-scale,micro-scale and micro-nano-scale hybrid silver sintered materials are separately presented.The emerging rapid sintering approaches,such as the electric-assisted approach,are briefly introduced and the technical outlook is provided.In addition,the study highlights the importance of creating a brief resource guide on using the correct sintering methods.