We have synthesized silver nanoparticles from silver nitrate solutions using extracts of
Rumex hymenosepalus
, a plant widely found in a large region in North America, as reducing agent. This plant ...is known to be rich in antioxidant molecules which we use as reducing agents. Silver nanoparticles grow in a single-step method, at room temperature, and with no addition of external energy. The nanoparticles have been characterized by ultraviolet-visible spectroscopy and transmission electron microscopy, as a function of the ratio of silver ions to reducing agent molecules. The nanoparticle diameters are in the range of 2 to 40 nm. High-resolution transmission electron microscopy and fast Fourier transform analysis show that two kinds of crystal structures are obtained: face-centered cubic and hexagonal.
Engineering of multifunctional drug nanocarriers combining stability and good release properties remains a great challenge. In this work, natural polymers κ-carrageenan (κ-CAR) and chitosan (CS) were ...deposited onto olive oil nanoemulsion droplets (NE) via layer-by-layer (LbL) self-assembly to study the release mechanisms of the anti-inflammatory diflunisal (DF) as a lipophilic drug model. The nano-systems were characterized by dynamic light scattering (DLS), zeta potential (ζ-potential) measurements, transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (XEDS) and Fourier transform infrared spectroscopy (FTIR) to confirm the NE-coating with polymer layers. In addition, kinetic release studies of DF were developed by the dialysis diffusion bag technique. Mathematical models were applied to investigate the release mechanisms. The results showed that stable and suitably sized nanocapsules (~300 nm) were formed. Also, the consecutive adsorption of polyelectrolytes by charge reversal was evidenced. More interestingly, the drug release mechanism varied depending on the number of layers deposited. The nanosized systems containing up to two layers showed anomalous transport and first order kinetics. Formulations with three and four layers exhibited Case II transport releasing diflunisal with zero order kinetics. Hence, our results suggest that these polyelectrolyte nanocapsules have great potential as a multifunctional nanocarrier for drug delivery applications.
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•RheoSAXS study evidencing a transition lamellar phase- multilamellar vesicles, that disappear after a short time.•The stability of foams made with these systems cannot be therefore ...due to vesicles.•The important role of the yield stress of the lamellar phases in the foam stability is discussed.
In order to formulate stable foams with gels, it is important to know their shear rheology properties. We illustrate this fact using a weak gel made of a lyotropic lamellar phase (SDS/hexanol/brine system). The effect of shear is investigated using rheology experiments coupled with Small Angle X-ray Scattering (rheo-SAXS) using synchrotron radiation. According to oscillatory tests, the samples exhibit a weak gel behavior. Steady state experiments evidence a shear-induced transition from lamellar to onion (multilamellar vesicle – MLV) textures at moderate shear rates. After the shear is stopped, there is a recovery from the onion texture to the initial lamellar texture within 30min, as directly demonstrated by the rheo-SAXS data. The lamellar to onion transition is therefore reversible. This excludes the possibility for the foams to be stabilized by onions adsorbed at the air–water interface as in foams made with other types of lamellar phases. In the example presented, the foam stability originates from the bulk rheological properties of the lamellar phase.
We have studied the external surface (elytra) of the Sonoran Desert beetle (
). Our aim was to assess whether this species has similar traits to some beetles from the Namibian Desert that are known ...to have hierarchical micropatterns that allow for water harvesting. We have conducted scanning electron microscopy (SEM) and apparent contact angle experiments on specimens collected at two sampling sites with different ambient humidity. The results show that the beetle's external surface microstructure is composed of a compact array of polygons with randomly scattered protuberances. The density of the polygons in the microstructure is different for individuals collected in different sites: the polygon array is denser in the more humid site and less dense in the drier site. The measured contact angles also depend on the sampling site. For individuals collected in the drier site, the average apparent contact angle is 70°, whereas for the more humid site, the average apparent contact angle is 92°. FT-IR experiments are consistent with the presence of hydrophobic wax compounds in the studied surfaces. Our investigation opens new questions that are currently being addressed by experiments that are underway. For instance, it would be interesting to know whether the observed nanopatterns could be used in biomimetic devices for water harvesting purposes.
The shrimp necrotizing hepatopancreatitis is caused by a pleomorphic Gram-negative Rickettsialike bacteria known as NHP-B. It is well known that silver is an effective bactericidal, but experiments ...with aquatic organisms are scarce, even more at nanoparticle level. The objective of this study was to determine the antibacterial effect of silver nanoparticles (AgNP) against NHP-B in the Pacific white shrimp Litopenaeus vannamei. For this, AgNO.sub.3 was used as source of silver, and extracts of dried leaves of green tea Camellia sinensis and neem tree Azadirachta indica as reducing agents. Different lots of infected shrimp received 0,5 and 35 microg of AgNP by forced feeding. The differences between the number of bacterial nodules in shrimp hepatopancreas and shrimp mortality relative to the amount of AgNP demonstrated to be effective against this pathogen.
Human consumption of sea urchin gonads has led to overexploitation of commercial species, and the search for new marketable species to promote the recovery of exploited populations. Echinometra ...vanbrunti is a promising candidate for commercial exploitation. Its annual reproductive cycle has an effect on the proximate composition of the gonads; if they were to be consumed, the best quality in biochemical composition was determined to be from December to May, when nutritive phagocytes uphold the highest contents of protein and lipid. They possess considerable levels of omega-3 essential fatty acids, predominantly eicosapentaenoic and docosahexaenoic (DHA) acids, quite important for human nutrition. A subtle trend of higher DHA levels during the growing, premature, and mature gonadal stages of females and males was observed, though it is strongly influenced by diet and environment. A program to protect and regulate the sustainable extraction needs to be put in place before commercial exploitation.
The Ostreid herpes virus type 1 (OsHV-1) is one of the most devastating pathogen in oyster cultures. Among several factors, as food limitation, oxygen depletion, salinity and temperature variations, ...episodes of “summer mortality” of the Pacific oyster Crassostrea gigas have also been associated with OsHV-1 infection. Mortalities of C. gigas spat and juveniles have increased significantly in Europe, and contemporary mortality records of this mollusk in México have been associated with the occurrence of OsHV-1. In the present study, the expression of the heat shock protein 70 gene from the Pacific oyster correlates with the abundance of DNA polymerase transcripts from the OsHV-1. This may suggest that the induction on the expression of the Pacific oyster hsp70 may potentially participate in the immune response against the virus. Furthermore, this study reports for the first time a TEM representative image of the OsHV-1 in aqueous solution, which possesses an icosahedral shape with a diameter of 70 nm × 100 nm. Finally, the examined sequence encoding the ORF4 of the OsHV-1 isolate from northwest Mexico showed specific sequence variations when compared with OsHV-1 isolates from distant geographical areas.
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•We studied the effect of OsHV-1 on the expression of C. gigas hsp70.•Hsp70 never returned to it amount of mRNA control organism level.•Hsp70 levels were related to the infection level.•In situ detection of host and pathogen genes in same tissues.•First negative aqueous TEM images of the OsHV-1.
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