In this work, we investigate the possibility of using magnetic nanoparticles embedded into the silica to locally heat up the silica-water interface where the increase in temperature of nanoparticles is induced by an external radio-frequency magnetic field. Through the use of the theoretical model, it is shown that such the process leads to an increase in the total negative charge of the silica surface due to the deprotonation of silanol groups. It is also shown that the efficiency of such an electric charging process depends on the size of nanoparticles. Moreover, the optimal size of nanoparticles allowing for a maximum charging efficiency is determined. This observation may prove to be very important from the point of view of potential applications as it may allow to fine-tune chemical reactions on the silica surface. Some aspects of this work related to the magnetically heated nanoparticles were verified by the experiment.
Distribution of the isoelectric point (pI) was calculated for the hypervariable regions of Fab fragments of the antibody molecules, which structure is annotated in the structural antibody database SabDab. The distribution is consistent with the universal for all organisms dividing the proteome into two sets of acidic and basic proteins. It shows the additional fine structure in a form of the narrow-sized peaks of pI values. This is an explanation why a small change of the environmental pH can have a strong effect on the antibody-antigen affinity. To show this, a typical enzyme-linked immunospecific assay experiment for testing the reaction of goat anti-human IgA antibodies with human IgA immunoglobulins of saliva as antigens was modified in such a way that Fe3O4magnetic nanoparticles were added to PBS buffer. The magnetic nanoparticles were remotely heated by the radio frequency magnetic field providing the local change of temperature and pH. It was observed that short times of the heating were significantly increasing the antibody-antigen binding strength while it was not the case for a longer time. The finding discussed in the study can be useful for biopharmaceuticals using antibodies, the immunoassay techniques as well as for control over the use of hyperthermia.
The study investigated the phenomenon of the fast aggregation of single-domain magnetic iron oxide nanoparticles in stable aqueous colloidal suspensions due to the presence of a radio-frequency (RF) magnetic field. Single-domain nanoparticles have specific magnetic properties, especially the unique property of absorbing the energy of such a field and releasing it in the form of heat. The localized heating causes the colloid to become unstable, leading to faster agglomeration of nanoparticles and, consequently, to rapid sedimentation. It has been shown that the destabilization of a stable magnetic nanoparticle colloid by the RF magnetic field can be used for the controlled filtration of larger agglomerates of the colloid solution. Two particular cases of stable colloidal suspensions were considered: a suspension of the bare nanoparticles in an alkaline solution and the silica-stabilized nanoparticles in a neutral solution. The obtained results are important primarily for biomedical applications and wastewater treatment.
Modified titanate nanotubes (TNT) were tested for their adsorption of methylene blue (MB) from water solutions. They were obtained from the TiO2 nanopowder using a standard alkaline hydrothermal method but in the stage of acid washing, when the titanate flakes begin to roll into nanotubes, magnetite nanoparticles were added. The Fe3O4 magnetic nanoparticles with diameter of around 2[Formula: see text]nm and 12[Formula: see text]nm were used in the tests. Significantly stronger adsorption of MB was observed when smaller nanoparticles were used compared to using larger nanoparticles and compared to the case of unmodified nanotubes. It was shown that the increased adsorption of MB is associated with a more negative value of [Formula: see text]-potential for titanates modified by the ultra-small nanoparticles. In the adsorption experiment, pH 7 was selected. These results may prove to be of great importance in the case of potential applications corresponding to the use of such material for wastewater purification.
Herein the effect is analyzed that magnetic dipole interactions have on the heating process of single‐domain magnetic nanoparticles subjected to an external radiofrequency (RF) magnetic field, where the magnetic nanoparticles are densely packed in a thin elastic film. To analyze this effect, the considered thin film is subjected to mechanical deformation, which causes the displacement of nanoparticles and affects magnetic dipole interactions between them. As a consequence, at different stages of the mechanical deformation, the film shows different heating powers of the magnetic nanoparticles. To investigate this effect, a theoretical model describing the considered nanoparticle system exposed to the RF magnetic field is proposed, where the heating power of the film is discussed in terms of the specific absorption rates (SARs). Through the use of this model, it is shown that the considered stretchable magnetic film can sense mechanical deformation in the presence of the uniform RF magnetic field both in the direction perpendicular to the film and in the loading direction. Thus, the concept proposed in this study can be utilized in the design of a sensor that would be particularly interesting in the case of medical applications for diagnostic purposes.
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