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Superparamagnetic iron oxide nanoparticlescoated with titaniumdioxide have been synthesized, growing the titanium dioxide directlyeither on the magnetic nuclei or on magnetic nanoparticles previouslycoated with a semihydrophobic silica layer. Both coatings have beenobtained by sol–gel. Since it is well-known that the existenceof the intermediate silica layer influences the physicochemical propertiesof the material, a detailed characterization of both types of coatingshas been carried out. The morphology, structure, and composition ofthe synthesized nanomatrices have been locally analyzed with subangstromspatial resolution, by means of aberration corrected transmissionelectron microscopy (HRTEM and STEM-HAADF). Besides magnetizationmeasurements, proton relaxivity experiments have been also performedon water suspensions of the as-synthesized nanoparticles to investigatethe role of the silica interlayer in the relaxometric properties.The silica interlayer leads to nanoparticles with much higher waterstability and to higher relaxivity of the suspensions. [ABSTRACT FROM AUTHOR]

Alginate nanobeads encapsulating magnetic cobalt ferrite nanoparticles are synthesized by an aerosol–ionotropic gelation method. The nanobeads are characterized in environmental‐like conditions by means of advanced electron microscopy techniques. The proposed synthetic method and the combination of the different electron microscopy techniques can be extended to design and characterize a variety of nanosized soft materials. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Iron oxide nanoparticles (NPs) are attractive materials for enzyme immobilization and, thanks to their superparamagnetism, can be accessed by remote stimuli. This can be exploited to activate molecules that are not remotely actuable. Here, we demonstrate that thermophilic enzymes chemically linked to NPs can be activated in a "wireless" fashion by an external alternate magnetic field (AMF). To this aim, we have conjugated, with different binding strategies, the thermophilic enzymes α-amylase and l -aspartate oxidase to iron oxide NPs obtaining NP-enzyme systems with activities depending on the different orientations and stretching of the enzymes. Since enzyme activation occurs without a significant rise of the "overall" temperature of the systems, we have speculated a local NP-enzyme heating that does not immediately interest the rest of the solution that remains at relatively low temperature, low enough to allow non-thermophilic enzymes to work together with the NP-conjugated thermophilic enzymes. Nanoactuation of thermophilic enzymes by AMF has potential applications in different fields. Indeed, multi-enzymatic processes with enzymes with different temperature optima could be carried out in the same reaction pot and thermolabile products could be efficiently produced by thermophilic enzymes without suffering for the high temperatures. Moreover, our findings represent a proof of concept of the possibility to achieve a fine-tuning of the enzyme-NP system with the aim to intervene in cell metabolism. [ABSTRACT FROM AUTHOR]

Enzyme immobilization on magnetic supports represents a great advantage for the industrial application of enzymatic catalysis since it allows an easy recovery of the catalyst, avoiding any contamination of the product by residual enzyme. Iron oxide nanoparticles are very useful for this purpose. Using a polymer to diminish the interaction between the magnetic cores themselves, can improve the colloidal stability of the support and prevent any interaction with the environment that would affect both support properties and enzyme stability. For this reason, in this work different magnetic micro-supports, based on polydopamine-coated iron oxide nanoparticles with a multi polysaccharide shell, have been developed. These supports have been used to immobilize chloroperoxidase, a very interesting enzyme, able to catalyze many reactions of large-scale interest, but whose application is limited by its sensitivity to reaction conditions. The multi polysaccharide shells of the supports were obtained through a combination of chitosan and alginate. An in-depth analysis of physicochemical and catalytic properties of all the developed magnetic supports is reported. CPO was successfully immobilized with an efficiency of entrapment between 92% and 100% in the case of supports with chitosan in the interior or outer shell respectively. A very good chemical stability of the support under reaction conditions was observed in the case of an interior shell of alginate and an outer coating of chitosan, together with an excellent reusability of the immobilized enzyme, that was recycled to catalyze up to 25 consecutive reaction cycles. [ABSTRACT FROM AUTHOR]