Characterization of self-assembled silver nanoparticle ink based on nanoemulsion method.
ABSTRACT: A well-dispersed self-assembled silver nanoparticles (AgNPs) ink with high purity was synthesized via AgNO3 emulsion prepared by blending an AgNO3 aqueous solution and a liquid paraffin solution of both polyoxyethylene (20) sorbitan monooleate (Tween 80) and sorbitan monooleate (Span 80). The ink remained as an emulsion at low temperatures; however, it produced AgNPs after sintering at about 60°C and showed a high stability at nanoscale sizes (with diameters ranging 8.6-13.4 nm) and a high conductivity. During the whole procedure, Tween 80 acted as a surfactant, reductant and stabilizer. Presumably, Tween 80 underwent an autoxidation process, where a free radical of an ?-carbon of ether oxygen was formed by hydrogen abstraction. The mean diameter of emulsion droplets could be reduced by decreasing water content and increasing the ratio of surfactant and concentration of AgNO3 aqueous solution. Consequently, the thermogravimetric analysis and X-ray diffraction result clarified the purity of the produced Ag0. Dynamic light scattering and ultraviolet-visible spectroscopy clarified that an increased concentration of AgNO3 decreased the particle size.
Project description:The addition of polyoxyethylene sorbitan monooleate (Tween 80) to a culture of mycobacteria greatly influences cell permeability and sensitivity to antibiotics but very little is known regarding the underlying mechanism. Here we show that Corynebacterium matruchotii (surrogate of mycobacteria) converts Tween 80 to a structural series of polyoxyethylenic acids which are then used to form novel series-2A and series-2B glycolipids. Minor series-3 glycolipids were also synthesized. The polyoxyethylenic acids replaced corynomycolic acids in the cell wall. Correspondingly the trehalose dicorynomycolate content was reduced. MALDI mass spectrometry, MS-MS, (1)H-NMR, and (13)C-NMR were used to characterize the series-2 glycolipids. Series-2A glycolipid is trehalose 6-C(36:2)-corynomycolate-6'-polyoxyethylenate and series-2B glycolipid is trehalose 6-C(36:2)-corynomycolate-6'-furan ring-containing polyoxyethylenate. Mycobacterium smegmatis grown in the presence of Tween 80 also synthesizes series-2 type glycolipids. The synthesis of these novel glycolipids in corynebacteria and mycobacteria should result in gross changes in the cell wall permeability and drug sensitivity.
Project description:Tubular liposomes containing a hydrophilic model compound (fluorescein sodium salt, FSS) were entrapped inside the internal aqueous phase (W(1)) of water-in-oil-in-water (W(1)/O/W(2)) double-emulsion globules. Our hypothesis was that the oil membrane of double emulsions can function as a layer of protection to liposomes and their contents and thus better control their release. Liposomes were prepared in bulk, and their release was observed microscopically from individual double-emulsion globules. The liposomes containing FSS were released through external coalescence, and the behavior of this system was monitored visually by capillary video microscopy. Double-emulsion globules were stabilized with Tween 80 as the water-soluble surfactant, with Span 80 as the oil-soluble surfactant, while the oil phase (O) was n-hexadecane. The lipids in the tubular liposomes consist of L-alpha-phosphatidylcholine and Ceramide-VI. Variations of Tween 80 concentration in the external aqueous phase (W(2)) and Span 80 concentration in the O phase controlled the release of liposomes from the W(1) phase to the W(2) phase. The major finding of this work is that the sheer presence of liposomes in the W(1) phase is by itself a stabilizing factor for double-emulsion globules.
Project description:Purpose:To potentiate the anticancer activity of curcumin (CUR) by improving its cell penetration potentials through formulating it into nanostructured lipid carriers (NLCs) and using the prepared NLCs in photodynamic therapy. Methods:A 3×4 factorial design was used to obtain 12 CUR-NLCs using two factors on different levels: (1) the solid lipid type at four levels and (2) the solid to liquid lipid ratio at three levels. Olive oil, Tween 80 and lecithin were chosen as liquid lipid, surfactant and co-surfactant, respectively. CUR-NLCs prepared by high shear hot homogenization method were evaluated by determination of particle size (PS), polydispersity index, zeta potential (ZP), entrapment efficiency percent, drug loading percent and in vitro drug release. Optimization was based on the evaluation results using response surface modeling (RSM). Optimized formulae were tested for their in vitro release pattern and for dark and photo-cytotoxic anticancer activity on breast cancer cell line in comparison to free CUR. Results:Evaluation tests showed the appropriateness of NLCs prepared from glyceryl monooleate and Geleol™ helped choosing two optimized formulae, PE3 and GE3. PE3 (prepared using glyceryl monooleate) showed enhanced release rates compared to GE3 (prepared from Geleol) and superior cytotoxic anticancer activity compared to both GE3 and free CUR under both light and dark conditions. The small mean PS, spherical shape as well as the negative ZP enhanced the internalization of the NLCs within cells. Modulation and inhibition of P-glycoprotein expression by glyceryl monooleate synergized the cytotoxic activity of CUR. Conclusion:CUR loading in NLCs enhanced its cell penetration and cytotoxic anticancer properties both in dark and in light conditions.
Project description:Surfactant-polymer mixtures are common in food, cosmetic and pharmaceutical products. These components can interact with each other. The interactions depend on the type of polymer and surfactant, the purity of the ingredients, the ionic content and their concentration. Therefore, the data presented here provide valuable information that could be useful for those working with these mixtures in different applications, particularly in blends with polyelectrolytes and their counterions. This article contains experimental data about the physicochemical characterization of sodium stearoyl lactylate (SSL), polyoxyethylene sorbitan monolaurate (Tween 20) and ?-carrageenan. Techniques included atomic absorption, DSC, FTIR-ATR, NMR, and surface tension.
Project description:The selective recovery of ultrafine, <10 ?m, particles remains a significant challenge in the minerals industry. Indeed, these particles often report to tailings impoundments, resulting in under-utilization of mined resources and the need for tailings dams. Recently, a technique has been developed offering the potential to selectively recover particles down to <1 ?m in size. This technique, originally inspired by oil agglomeration, uses a high internal-phase water in oil emulsion as a binder to selectively agglomerate hydrophobic particles. Due to the significant concentration of the dispersed aqueous phase, ~95%, the continuous organic phase forms a network of very thin, permeable films, estimated to be 60 nm thick. These are stabilized by an emulsifier. In the high shear field of the agglomeration process, the binder is fragmented into smaller hydrophobic portions, delivering its thin film coating to the adhering hydrophobic particles. Permeation of water across the thin films eliminates the viscous hydrodynamic resistance, permitting sub-micron particle recovery to occur at rates similar to those for particles considerably larger in size. This recovery occurs within seconds under intense mixing. In this study, a model system consisting of magnetite, with a Sauter mean diameter of 11.4 ?m, was agglomerated using the water in oil emulsion binder. The binder, which contained the emulsifier sorbitan monooleate, appeared to also act as a collector for the magnetite, thus no separate particle conditioning step was required. Curiously, however, the binder requirements were higher than expected. Further investigations concerning the stability of the binder revealed that the magnetite particles were causing rapid binder degradation. Therefore, prior to agglomeration using the binder, the particles were conditioned with sorbitan monooleate to render them hydrophobic. This pre-conditioning led to significant reductions in the binder dosage required to achieve agglomeration. Moreover, the resulting dosage matched that predicted by a model silica system for the same specific hydrophobic surface area, thus allowing a model to be validated based on the required binder dosage for a known hydrophobic surface area. Examination of binder stability in the presence of conditioned magnetite revealed that the now hydrophobic particles stabilized the binder.
Project description:The need for the precise and reliable collection of potential biothreat contaminants has motivated research in developing a better understanding of the variability in biological surface sampling methods. In this context, the objective of this work was to determine parameters affecting the efficiency of extracting Bacillus anthracis Sterne spores from commonly used wipe sampling materials and to describe performance using the interfacial energy concept. In addition, surface thermodynamics was applied to understand and predict surface sampling performance. Wipe materials were directly inoculated with known concentrations of B. anthracis spores and placed into extraction solutions, followed by sonication or vortexing. Experimental factors investigated included wipe material (polyester, cotton, and polyester-rayon), extraction solution (sterile deionized water [H(2)O], deionized water with 0.04% Tween 80 [H(2)O-T], phosphate-buffered saline [PBS], and PBS with 0.04% Tween 80 [PBST]), and physical dissociation method (vortexing or sonication). The most efficient extraction from wipes was observed for solutions containing the nonionic surfactant Tween 80. The increase in extraction efficiency due to surfactant addition was attributed to an attractive interfacial energy between Tween 80 and the centrifuge tube wall, which prevented spore adhesion. Extraction solution significantly impacted the extraction efficiency, as determined by statistical analysis (P < 0.05). Moreover, the extraction solution was the most important factor in extraction performance, followed by the wipe material. Polyester-rayon was the most efficient wipe material for releasing spores into solution by rank; however, no statistically significant difference between polyester-rayon and cotton was observed (P > 0.05). Vortexing provided higher spore recovery in H(2)O and H(2)O-T than sonication, when all three wipe materials and the reference control were considered (P < 0.05).
Project description:In Saccharomyces cerevisiae, acyl-coenzyme A desaturation by Ole1 requires molecular oxygen. Tween 80, a poly-ethoxylated sorbitan-oleate ester, is therefore routinely included in anaerobic growth media as a source of unsaturated fatty acids (UFAs). During optimization of protocols for anaerobic bioreactor cultivation of this yeast, we consistently observed growth of the laboratory strain S. cerevisiae CEN.PK113-7D in media that contained the anaerobic growth factor ergosterol, but lacked UFAs. To minimize oxygen contamination, additional experiments were performed in an anaerobic chamber. After anaerobic precultivation without ergosterol and Tween 80, strain CEN.PK113-7D and a congenic ole1? strain both grew during three consecutive batch-cultivation cycles on medium that contained ergosterol, but not Tween 80. During these three cycles, no UFAs were detected in biomass of cultures grown without Tween 80, while contents of C10 to C14 saturated fatty acids were higher than in biomass from Tween 80-supplemented cultures. In contrast to its UFA-independent anaerobic growth, aerobic growth of the ole1? strain strictly depended on Tween 80 supplementation. This study shows that the requirement of anaerobic cultures of S. cerevisiae for UFA supplementation is not absolute and provides a basis for further research on the effects of lipid composition on yeast viability and robustness.
Project description:The effects of oil droplet size and the formation of an interfacial protein film (IPF) on silver carp myofibrillar protein (MP)-oil composite gels were studied. MP- or Tween 80-stabilized camellia seed oil emulsions with different droplet sizes were prepared and added to MPs to prepare composite gels. The oil droplet size of the Tween 80-stabilized emulsion was significantly smaller (p < 0.05) than that of the MP-stabilized emulsion with the same homogenization speed. However, polymerization of Tween 80-stabilized emulsions during the preparation of the composite gels was found. Composite gels with the MP-stabilized emulsions of a small droplet size showed significantly improved water-holding capacity, texture, and dynamic rheological properties. Interfacial shear rheology studies revealed that the storage modulus (G') of the MP-stabilized emulsion composite gels was higher than that of the Tween 80-stabilized gels, and the tan ? of the MP-stabilized oil emulsion composite gels was smaller than that of the Tween 80-stabilized gels, indicating that stronger elastic gel structures were formed. These results suggested that the IPF formed in the MP-stabilized emulsion helped stabilize the oil droplets embedded in the protein gel network, and the smaller the droplet size, the more stable the composite gel. This work provides a better understanding of how oil emulsions interact with protein and affect the properties of MP-oil composite gels.
Project description:A bacterial isolate capable of tolerating 30 mM silver nitrate (AgNO3) was recovered from soil contaminated with industrial waste. The isolate was identified by 16S rRNA as Enterobacter cloacae Ism26 (KP988024) and its capability to synthesize silver nanoparticles (AgNPs) was investigated. AgNPs were produced by mixing 1 mM AgNO3 solution with bacterial cell lysate under light conditions. The UV-Vis spectrum of the aqueous medium containing AgNPs exhibited a peak at 440 nm corresponding to the surface plasmon resonance of the AgNPs. The crystalline nature of the particles was confirmed by X-ray difractometer. High-resolution transmission electron microscopy revealed that the AgNPs were spherical and well dispersed and ranged in size from 7 to 25 nm. The average size range of the produced AgNPs was confirmed by dynamic light scattering. Fourier transform infrared spectroscopy revealed possible involvement of reductive groups on the surface of the nanoparticles. The biosynthesized AgNPs were stable for 6 months and inhibited both gram-positive and gram-negative bacteria. This work describes the exploitation of a low-cost biomaterial and an easy method for the synthesis of AgNPs with desirable and advantageous characteristics.
Project description:Continuous formation and utilization of nanoparticles (NPs) have resulted into significant discharge of nanosized particles into the environment. NPs find applications in numerous products and agriculture sector, and gaining importance in recent years. In the present study, silver nanoparticles (AgNPs) were biosynthesized from silver nitrate (AgNO3) by green synthesis approach using Aloe vera extract. Mustard (Brassica sp.) seedlings were grown hydroponically and toxicity of both AgNP and AgNO3 (as ionic Ag+) was assessed at various concentrations (1 and 3 mM) by analyzing shoot and root length, fresh mass, protein content, photosynthetic pigments and performance, cell viability, oxidative damage, DNA degradation and enzyme activities. The results revealed that both AgNPs and AgNO3 declined growth of Brassica seedlings due to enhanced accumulation of AgNPs and AgNO3 that subsequently caused severe inhibition in photosynthesis. Further, the results showed that both AgNPs and AgNO3 induced oxidative stress as indicated by histochemical staining of superoxide radical and hydrogen peroxide that was manifested in terms of DNA degradation and cell death. Activities of antioxidants, i.e., ascorbate peroxidase (APX) and catalase (CAT) were inhibited by AgNPs and AgNO3. Interestingly, damaging impact of AgNPs was lesser than AgNO3 on Brassica seedlings which was due to lesser accumulation of AgNPs and better activities of APX and CAT, which resulted in lesser oxidative stress, DNA degradation and cell death. The results of the present study showed differential impact of AgNPs and AgNO3 on Brassica seedlings, their mode of action, and reasons for their differential impact. The results of the present study could be implied in toxicological research for designing strategies to reduce adverse impact of AgNPs and AgNO3 on crop plants.