Stabilization and functionalization of iron oxide nanoparticles for biomedical applications

Superparamagnetic iron oxide nanoparticles (NPs) are used in a rapidly expanding number of research and practical applications in the biomedical field, including magnetic cell labeling separation and tracking, for therapeutic purposes in hyperthermia and drug delivery, and for diagnostic purposes, e.g., as contrast agents for magnetic resonance imaging. These applications require good NP stability at physiological conditions, close control over NP size and controlled surface presentation of functionalities. This review is focused on different aspects of the stability of superparamagnetic iron oxide NPs, from its practical definition to its implementation by molecular design of the dispersant shell around the iron oxide core and further on to its influence on the magnetic properties of the superparamagnetic iron oxide NPs. Special attention is given to the selection of molecular anchors for the dispersant shell, because of their importance to ensure colloidal and functional stability of sterically stabilized superparamagnetic iron oxide NPs. We further detail how dispersants have been optimized to gain close control over iron oxide NP stability, size and functionalities by independently considering the influences of anchors and the attached sterically repulsive polymer brushes. A critical evaluation of different strategies to stabilize and functionalize core-shell superparamagnetic iron oxide NPs as well as a brief introduction to characterization methods to compare those strategies is given.     

High-density gold nanowire arrays by lithographically patterned nanowire electrodeposition

Here we describe a new method for preparing multiple arrays of parallel gold nanowires with dimensions and separation down to 50 nm. This method uses photolithography to prepare an electrode consisting of a patterned nickel film on glass, onto which a gold and nickel nanowire array is sequentially electrodeposited. After the electrodeposition, the nickel is stripped away, leaving behind a gold nanowire array, with dimensions governed by the gold electrodeposition parameters, spacing determined by the nickel electrodeposition parameters, and overall placement and shape dictated by the photolithography.     

Chemical - Looping with oxygen uncoupling using Mn/Mg-based oxygen carriers - Oxygen release and reactivity with methane

Chemical-looping combustion with oxygen uncoupling (CLOU) is a method for combustion of solid and gaseous fossil fuels, which enables easy separation of carbon dioxide from the gaseous product mixture. In contrast to the related chemical-looping combustion (CLC) technology where gaseous or gasified fuels react directly with oxygen carriers, CLOU processes require oxygen carrier materials to be able to release oxygen in the fuel reactor and to regenerate by re-oxidation in oxygen-rich atmosphere in the air reactor at elevated temperature. Oxygen uncoupling properties and reactivities for methane combustion of 12 oxygen carrier particles, produced from mixtures of manganese and magnesium oxides with optional addition of titanium dioxide or calcium hydroxide, are investigated in a quartz batch reactor at 810 °C, 850 °C, 900 °C and 950 °C. All investigated oxygen carriers have oxygen release characteristics. The addition of calcium hydroxide facilitates oxygen release and combustion of methane, whereas addition of titanium dioxide does not have a pronounced effect on either oxygen uncoupling or reactivity of the oxygen carrier. In general, particles with greater extent of oxygen release have superior methane combustion properties.     

Crosslinking of polybenzimidazole membranes by divinylsulfone post‐treatment for high‐temperature proton exchange membrane fuel cell applications

Phosphoric acid‐doped polybenzimidazole (PBI) has been suggested as a promising electrolyte for proton exchange membrane fuel cells operating at temperatures up to 200 °C. This paper describes the development of a crosslinking procedure for PBI membranes by post‐treatment with divinylsulfone. The crosslinking chemistry was studied and optimized on a low‐molecular‐weight model system and the results were used to optimize the crosslinking conditions of PBI membranes. The crosslinked membranes were characterized with respect to chemical and physiochemical properties, showing improved mechanical strength and oxidative stability compared with their linear analogues. Fuel cell tests were further conducted in order to demonstrate the feasibility of the crosslinked membranes. Copyright © 2011 Society of Chemical Industry     

Shear-induced 1-D alignment of alumina nanoparticles in coatings

Atomic Force Microscopy and Scanning Electron Microscopy were used to study shear-induced alignment of alumina and silica nanoparticles in two-component polyurethane clear coatings. 1-D strings of nanoparticles, formed in an extended pearl-necklace fashion were observed near the surfaces of cured films at nanoparticle volume fractions less than 0.05. This alignment is affected by the shear conditions of the application method. When applied by spraying, linear particle strings as long as 5 cm were observed in the direction of shear. Nanoparticle strings were also found, to a lesser extent, when coatings were applied by a drawdown method. The phenomenon was not observed in coatings applied with minimal shear. These particle string formations, in addition to affecting the performance of coatings, may have broader implications in the field of nanomaterials. Our literature searches so far have not uncovered reports of stable, 1-D nanoparticle arrangements with same degree of linearity produced under simple shear with compositions having very low particle loadings. Presented at the 2006 FutureCoat! conference, sponsored by the Federation of Societies for Coatings Technology, in New Orleans, LA, on November 1–3, 2006.     

Notwendigkeit und Vermarktung von Flexibilitätsoptionen im Energiesystem der Zukunft

Demands on production, distribution and consumption of electrical energy change fundamentally with the energy revolution. Energy purchasing costs for inflexible consumers are rising and proceeds of inflexible producers are sinking. Companies are able to reduce costs by marketing operational flexibility options. This article sets out the need of flexibility in the energy system and the new marketing options. Flexibility potentials within infrastructure plants of a chemical park are analyzed, evaluated regarding marketing and activated in the presented research project FlexChemistry.     

Porous Perovskite Fibers – Preparation by Wet Phase Inversion Spinning and Catalytic Activity

Porous perovskite (LaMnO₃) fibers were prepared by means of wet phase inversion spinning. The influence of different spinning procedures, slurry and coagulation bath composition on fiber shape and pore morphology was studied. The catalytic activity of the prepared fibers was tested for carbon monoxide oxidation as a model reaction in a differential recycle reactor. The results revealed that by suitable choice of process conditions porous catalytically active fibers can be prepared. Catalytic measurements confirmed that the catalytic fibers exhibit an open structure that allows full utilization of the catalytically active surface without intraparticle diffusional limitations.     

Real time monitoring of bioreactor mAb IgG3 cell culture process dynamics via Fourier transform infrared spectroscopy: Implications for enabling cell culture process analytical technologyŽ 

Compared to small molecule process analytical technology (PAT) applications, biotechnology product PAT applications have certain unique challenges and opportunities. Understanding process dynamics of bioreactor cell culture process is essential to establish an appropriate process control strategy for biotechnology product PAT applications. Inline spectroscopic techniques for real time monitoring of bioreactor cell culture process have the distinct potential to develop PAT approaches in manufacturing biotechnology drug products. However, the use of inline Fourier transform infrared (FTIR) spectroscopic techniques for bioreactor cell culture process monitoring has not been reported. In this work, real time inline FTIR Spectroscopy was applied to a lab scale bioreactor mAb IgG3 cell culture fluid biomolecular dynamic model. The technical feasibility of using FTIR Spectroscopy for real time tracking and monitoring four key cell culture metabolites (including glucose, glutamine, lactate, and ammonia) and protein yield at increasing levels of complexity (simple binary system, fully formulated media, actual bioreactor cell culture process) was evaluated via a stepwise approach. The FTIR fingerprints of the key metabolites were identified. The multivariate partial least squares (PLS) calibration models were established to correlate the process FTIR spectra with the concentrations of key metabolites and protein yield of in-process samples, either individually for each metabolite and protein or globally for all four metabolites simultaneously. Applying the 2^nd derivative pre-processing algorithm to the FTIR spectra helps to reduce the number of PLS latent variables needed significantly and thus simplify the interpretation of the PLS models. The validated PLS models show promise in predicting the concentration profiles of glucose, glutamine, lactate, and ammonia and protein yield over the course of the bioreactor cell culture process. Therefore, this work demonstrated the technical feasibility of real time monitoring of the bioreactor cell culture process via FTIR spectroscopy. Its implications for enabling cell culture PAT were discussed.     

Changes in Molecular Characteristics of Cereal Carbohydrates after Processing and Digestion

Different extraction, purification and digestion methods were used to investigate the molecular properties of carbohydrates in arabinoxylan and β-glucan concentrates, dietary fiber (DF) rich breads and ileum content of bread fed pigs. The breads studied were: a low DF wheat bread (WF), whole meal rye bread (GR), rye bread with kernels (RK), wheat bread supplemented with wheat arabinoxylan concentrate (AX) and wheat bread supplemented with oat β-glucan concentrate (BG). The weight average molecular weight (M_w) of extractable carbohydrates in β-glucan concentrate decreased eight-fold after inclusion in the BG bread when exposed to in vitro digestion, while the M_w of purified extractable carbohydrates in AX bread was reduced two-fold, and remained almost unaffected until reaching the terminal ileum of pigs. Similarly, the M_w of purified extractable carbohydrates in GR and RK bread was not significantly changed in the ileum. The AX bread resulted in the highest concentration of dissolved arabinoxylan in the ileum among all the breads that caused a substantial increased in ileal AX viscosity. Nevertheless, for none of the breads, the M_w of extractable carbohydrates was related neither to the bread extract nor ileal viscosity.