Biodegradation of nanoparticles includes the destruction of a stabilizing coating and the accompanying change in interparticle interaction, as well as the direct destruction of the inorganic nuclei ...of particles. These processes lead to characteristic changes in the shape of the Mössbauer spectra of iron oxide nanoparticles. In this work, we investigated the in vitro biodegradation of 57Fe-based magnetic nanoparticles with the aid of Mössbauer spectroscopy. For this purpose, two types of magnetic nanoparticles enriched with the 57Fe isotope were synthesized. Copolymer Pluronic F-127 and citric acid were used to stabilize nanoparticles in aqueous medium. Moreover, synthesized nanoparticles were analyzed by physicochemical methods and investigated for cytotoxicity. The study of magnetic nanoparticles biodegradation was performed on 4 T1 cell culture (breast cancer). We measured Mössbauer spectra of nanoparticles incubated with 4 T1 cells and spectra of control nanoparticle samples at different conditions. The analysis of spectra was carried out in the many-state relaxation model formalism. The study revealed that after 120-hours incubation of nanoparticles in cells, they did not undergo measurable changes typical of biodegradation processes. Nevertheless, we noted intense intracellular oxidation of ferrous iron of synthesized nanoparticles to the ferric phase. The results obtained indicate the possibility of using the obtained nanoparticles in Mössbauer in vitro studies.
The effect of measurement conditions and the nature of the plasticizer of an ion-selective electrode membrane (
ortho
-nitrophenyloctyl ether, dinonyl adipate, dibutyl phthalate) on the main ...performance characteristics of clotrimazole-selective electrodes with polyvinyl chloride ion-exchange membranes containing potassium tetrakis(4-chlorophenyl)borate as an ion exchanger was studied. The introduction of small (up to 20%) ethanol additives into the aqueous solution leads to a significant improvement of the potential stability and expands the working range of the electrodes. All of the studied electrodes have high selectivity to clotrimazole with respect to both inorganic and organic cations, slope of the electrode function close to the theoretical value, and low limits of detection (5.0 × 10
–8
–7.5 × 10
–8
M). An electrode with a membrane plasticized with
ortho
-nitrophenyloctyl ether was the best for the combination of characteristics. It was demonstrated that clotrimazole can be determined in model solutions and various dosage forms (spray, cream, suppositories, tablets) using direct potentiometry and potentiometric titration with sodium tetraphenylborate. The proposed procedures are rapid (10–15 min) and characterized by excellent reproducibility (the relative standard deviation does not exceed 1.2%).
The line broadening in the Mössbauer spectra of nanoparticles in model colloids with known viscosity has been studied. Magnetite nanoparticles with average hydrodynamic sizes of 140 and 40 nm and a ...set of stable aqueous colloids based on them have been synthesized. The nanoparticles have been enriched in the
57
Fe isotope to compensate for the significant decrease in the Mössbauer effect probability in liquid media. Two series of temperature experiments have been carried out: in an aqueous colloid of nanoparticles with a 90-% glycerol content and on dehydrated samples of nanoparticles in the absence of Brownian motion. It is established that the Brownian motion of nanoparticles causes an additional broadening of Mössbauer lines, which is inversely proportional to the viscosity and nanoparticle size. It is demonstrated that Mössbauer spectroscopy allows one to separate the contributions of the Brownian motion and the Néel relaxation of magnetic nanoparticles. It is confirmed that the shape of Mössbauer spectrum and the probability of Mössbauer effect depend strongly on both the size of particles suspended in a liquid and the dynamic viscosity coefficient of the liquid.
•A new method of imaging of magnetic nanoparticles in biological objects is proposed.•The method uses quasi-random fluctuations of the particles in geomagnetic field.•The method has ability to ...determine the direction of motion of those particles.
Any existing method of visualization of magnetic nanoparticles in biological objects provides for imposing of an external magnetic field on the object under study. The field can considerably change the space distribution and properties of the nanomagnetic ensemble under study. In our work a SQUID-based magnetoencephalography device was used for the measurement of a magnetic noise generated by superparamagnetic nanoparticles based ferrofluid in the stationary standing vial without imposing of an external magnetic field. It was demonstrated that the ferrofluid generates spontaneous magnetic fields sufficient for its localization inside the experimental setup. Besides it was revealed that the spontaneous magnetic fields at certain frequencies have a strong spatial anisotropy. The detected effect can essentially increase the spatial resolution of the proposed method of visualization of magnetic nanoparticles in biological objects without using the external magnetic field.
An approach to the analysis of intracellular motion with nanosecond temporal resolution, based on the Mössbauer study of particles incorporated into a cell, has been developed. A possibility of ...applying magnetic nanoparticles as probes for studying in vitro the cytoplasm properties is analyzed. Two types of aqueous colloids of nanoparticles enriched with the
57
Fe isotope are synthesized, and their cytotoxicity and biodegradation resistance under living cell conditions are investigated by an example of breast cancer cell line. It is found that the particles barely undergo any changes characteristic of biodegradation processes during their 120-h incubation in cells, although intracellular oxidation of divalent iron in the particle composition is observed. This result indicates possibility of using these particles for in vitro Mössbauer studies.
A mixture of iron carbides and fullerene C
60
formed by electric arc synthesis has been hydroxylated by adding OH groups to the fullerene surface, which made it possible, according to the EXAFS data, ...to obtain almost pure fullerenol Fe@C
60
(OH)
30
. Powder samples of the fullerenol and the product obtained after its dehydroxylation have been examined using Mössbauer spectroscopy. The Mössbauer spectra have been processed under the assumption of superposition of three partial doublets of spectral lines. It is established that two doublets due to Fe
3+
dominate in the fullerenol spectrum. For the reduced fullerene Fe@C
60
sample, two doublets are due to Fe
3+
and the Fe
2+
doublet dominates. Thus, attachment of OH groups from the outer side of the fullerene carbon frame increases the oxidation state of iron, which shows that the iron atom is located inside the frame.
SQUID-based magnetoencephalography device was used for the measurement of a magnetic noise generated by ferrofluid in the stationary standing vial. It was found that a free surface of the ferrofluid ...generates spontaneous magnetic field sufficient to detect the presence of nanoparticles in the experimental setup. The spatial distribution of elementary magnetic sources was reconstructed by the frequency-pattern analysis of multichannel time series. The localization of ferrofluids was performed based on the analysis of quasirandom time series in two cases of oscillation source. One of them was infrasound from outer noise, and another one was the human heartbeat. These results are prospective for 3D imaging of magnetic particles without pre-magnetization.
•A new method of imaging of magnetic nanoparticles in human body is proposed.•The method uses quasi-random fluctuations of the particles in geomagnetic field.•The use of heartbeats as a source of such fluctuations is demonstrated.
The theory and method for analysis of Mössbauer spectra of magnetic nanoparticles in a fluid have been developed by generalizing the model of the magnetic dynamics of a Néel ensemble of ...antiferromagnetic particles to the case of ferrimagnetic iron oxides. The resulting model describing the “superposition” of the magnetic dynamics and translational motion of nanoparticles in ferrofluids has been tested in application to the simultaneous analysis of Mössbauer spectra of “dry” magnetite nanoparticles and the same particles in glycerol.
In this work was proposed a new radiotherapy enhancement method consisting of the administration of magnetic nanoparticles into the cells with further irradiation with a gamma-ray beam. As a result, ...adjusting the energy distribution of a gamma-ray beam and
57
Fe abundance it is possible to achieve an extremely intensive electron emission because of a nuclear resonance. The produced conversion and Auger electrons can be used as an effective tool for DNA lesions production. We developed a Monte Carlo model for an electron and gamma emission by
57
Fe nucleus using the Geant4 program package. The parameters of a resonant absorption were taken from Mössbauer spectra of magnetite nanoparticles synthesized for the administration into live cells. The space distribution of the radiation dose showed an increase in the dose of 2–2.5 times in the case of the natural abundance and more than 50 times in the case of the 66 % enrichment of the nanoparticles.
Two samples with immobilized magnetic nanoparticles are synthesized and investigated. The first sample has randomly oriented easy axes of magnetic anisotropy; the second sample has preferentially ...aligned easy axes, produced via the precipitation of a colloid of ferromagnetic particles in the presence of a magnetic field. It is shown that the precipitation of an aqueous suspension of nanoparticles in the presence of a magnetic field greatly changes the anisotropy of a sample, compared to one prepared by precipitation without a magnetic field. The second sample exhibits a preferential direction of the easy axes of magnetic anisotropy that coincides with the direction of the external magnetic field applied in the drying process of sample preparation.
