No abstract

The detection of superparamagnetic nanoparticles using NMR logging has the potential to provide enhanced contrast in oil reservoir rock formations. The stability of the nanoparticles is critical because the NMR relaxivity (R(2) ≡ 1/T(2)) is dependent on the particle size. Here we use a molecular theory to predict and validate experimentally the stability of citric acid-coated/PEGylated iron oxide nanoparticles under different pH conditions (pH 5, 7, 9, 11). The predicted value for the critical surface coverage required to produce a steric barrier of 5k(B)T for PEGylated nanoparticles (MW 2000) was 0.078 nm(-2), which is less than the experimental value of 0.143 nm(-2), implying that the nanoparticles should be stable at all pH values. Dynamic light scattering (DLS) measurements showed that the effective diameter did not increase at pH 7 or 9 after 30 days but increased at pH 11. The shifts in NMR relaxivity (from R(2) data) at 2 MHz agreed well with the changes in hydrodynamic diameter obtained from DLS data, indicating that the aggregation behavior of the nanoparticles can be easily and quantitatively detected by NMR. The unexpected aggregation at pH 11 is due to the desorption of the surface coating (citric acid or PEG) from the nanoparticle surface not accounted for in the theory. This study shows that the stability of the nanoparticles can be predicted by the theory and detected by NMR quantitatively, which suggests the nanoparticles to be a possible oil-field nanosensor.

Superparamagnetic iron oxide nanoparticles (SPIONs) are currently unavailable as MRI contrast agents for detecting atherosclerosis in the clinical setting because of either low signal enhancement or safety concerns. Therefore, a new generation of SPIONs with increased circulation time, enhanced image contrast, and less cytotoxicity is essential. In this study, monodisperse SPIONs were synthesized and coated with polyethylene glycol (PEG) of varying molecular weights. The resulting PEGylated SPIONs were characterized, and their interactions with vascular smooth muscle cells (VSMCs) were examined. SPIONs were tested at different concentrations (100 and 500 ppm Fe) for stability, T2 contrast, cytotoxicity, and cellular uptake to determine an optimal formulation for in vivo use. We found that at 100 ppm Fe, the PEG 2K SPIONs showed adequate stability and magnetic contrast, and exhibited the least cytotoxicity and nonspecific cellular uptake. An increase in cell viability was observed when the SPION-treated cells were washed with PBS after one hour incubation compared to 5 and 24 hour incubation without washing. Our investigation provides insight into the potential safe application of SPIONs in the clinic.

Red king crab and snow crab have both become important species for the Norwegian seafood industry. Since the first commercial harvest of red king crab in 2002 and of snow crab in 2012, the Norwegian seafood industry has developed new technology and knowledge for handling these species. This includes new fishing gear, conditions for live storage and processing, handling of byproducts, and entrance into new markets. The total Norwegian quota for red king crab increased from 220 metric tons in 2002 to 2350 metric tons in 2017, with a free-red king crab harvesting zone to the west of the quota-regulated area to prevent further expansion of the crab. At present, there is no established quota for snow crab. In 2016, a volume of about 5300 metric tons of snow crab was landed in Norway. In 2016, the export of red king crab and snow crab in Norway amounted to 529 million and 338 million Norwegian Kroner, respectively. Based on regular surveys of crab populations in the Barents Sea, it is assumed that the volumes red king crab and snow crab will remain steady and increase, respectively. Thus, these industries will continue to be important to the Norwegian seafood industry.

Monodisperse gas microbubbles, encapsulated with a shell of photopolymerizable diacetylene lipids and phospholipids, were produced by microfluidic flow focusing, for use as ultrasound contrast agents. The stability of the polymerized shell microbubbles against both aggregation and gas dissolution under physiological conditions was studied. Polyethylene glycol (PEG) 5000, which was attached to the diacetylene lipids, was predicted by molecular theory to provide more steric hindrance against aggregation than PEG 2000 and this was confirmed experimentally. The polymerized shell microbubbles were found to have higher shell-resistance than nonpolymerizable shell microbubbles and commercially available microbubbles (Vevo MicroMarker). The acoustic stability under 7.5 MHz ultrasound insonation was significantly greater than for the two comparison microbubbles. The acoustic stability was tunable by varying the amount of diacetylene lipid. Thus, our polymerized shell microbubbles are a promising platform for ultrasound contrast agents.

Superparamagnetic iron oxide (SPIO) nanoparticles have the potential to be used in the characterization of porous rock formations in oil fields as a contrast agent for NMR logging because they are small enough to traverse through nanopores and enhance contrast by shortening NMR T2 relaxation time. However, successful development and application require detailed knowledge of particle stability and mobility in reservoir rocks. Because nanoparticle adsorption to sand (SiO2) and rock (often CaCO3) affects their mobility, we investigated the thermodynamic equilibrium adsorption behavior of citric acid-coated SPIO nanoparticles (CA SPIO NPs) and poly(ethylene glycol)-grafted SPIO nanoparticles (PEG SPIO NPs) on SiO2 (silica) and CaCO3 (calcium carbonate). Adsorption behavior was determined at various pH and salt conditions via chemical analysis and NMR, and the results were compared with molecular theory predictions. Most of the NPs were recovered from silica, whereas far fewer NPs were recovered from calcium carbonate because of differences in the mineral surface properties. NP adsorption increased with increasing salt concentration: this trend was qualitatively explained by molecular theory, as was the role of the PEG grafting in preventing NPs adsorption. Quantitative disagreement between the theoretical predictions and the data was due to NP aggregation, especially at high salt concentration and in the presence of calcium carbonate. Upon aggregation, NP concentrations as determined by NMR T2 were initially overestimated and subsequently corrected using the relaxation rate 1/T2, which is a function of aggregate size and fractal dimension of the aggregate. Our experimental validation of the theoretical predictions of NP adsorption to minerals in the absence of aggregation at various pH and salt conditions demonstrates that molecular theory can be used to determine interactions between NPs and relevant reservoir surfaces. Importantly, this integrated experimental and theoretical approach can be used to gain insight into NP mobility in the reservoir.

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Aquaculture is one of the most resource-efficient and sustainable ways to produce animal protein. The Food and Agriculture Organization predicts that cultivated aquatic species will provide around 53% of the world's seafood supply by 2030.Further growth of intensive farmed aquatic species may be limited by a shortage of feed resources. The aquaculture sector therefore needs to intensify its search for alternative ingredients based on renewable natural resources. A significant increase in production will require an accelerated transition in technology and production systems, better use of natural available resources, development of high-quality alternative feed resources and exploitation of available space. The present review discusses the urgent need to identify appropriate alternative ingredients for a sustainable future salmonid production. We describe and evaluate the most promising marine ingredients, including low-trophic species (mesopelagic fish, zooplankton, polychaetes, macroalgae and crustaceans), novel microbial ingredients (bacteria, yeast and microalgae), insects (black soldier fly, yellow meal worm and crickets), animal byproducts (poultry meal, meat and bone meal, blood meal and hydrolysed feather meal) and by-products from other commercial productions (trimmings and blood). Furthermore, we discuss the available volumes and need for new processing technologies and refining methods to ensure commercial production of nutritionally healthy ingredients. The essential production steps and considerations for future development of sustainable and safe seafood production are also discussed.