Hyperthermia using magnetic particles is a very promising cancer therapy. In previous studies, we developed a mixture of magnetic micro/nanoparticles with high heating efficiency for tumor treatment and considerable change in permeability around therapeutic temperature for monitoring its temperature and position during heating. In this study, we examined experimentally the effect of applied magnetic field on the heating and permeability properties of the proposed mixture by manipulating the amplitude and frequency (H = 1.8–7.1 kA/m, f = 500 kHz, and H = 4.8 kA/m, f = 200–1000 kHz). It was found that the specific absorption rate (SAR) of the mixture increased with the amplitude and frequency (SAR α H1.68×f). Its intensity of magnetization (μ0M) at 20°C changed linearly with the amplitude, whereas it remained almost unchanged with the frequency. The results obtained here may enable us to find the optimal conditions of the applied magnetic field and the amount of magnetic particles required to treat a tumor of a given size.
This study describes a user-friendly and rapid detection system of oral bacteria in the liquid phase for point of care testing based on magnetic immunoassay. We focused on the dependence of the strength of external magnetic field required to switch the magnetic moments of nanoparticles bound to bacteria on the bacteria concentration. The results obtained indicate that the required field strength increases linearly as a function of log concentration of Porphyromonas gingivalis cultured in the range of 103–109 CFU/mL. Similarly, the required field strengths for Streptococcus mutans and Pseudomonas aeruginosa increase monotonically when their concentrations increase, whereas the required field strength for Escherichia coli decreases monotonically when its concentration increases. We then measured the concentration of Porphyromonas gingivalis in the saliva collected from elderly people in a geriatric health services facility and the results using the developed system had a correlation with those using a commercial bacteria counter.
Self-controlled heating mediators for magnetic hyperthermia are widely studied. In previous studies, we succeeded in developing a microsize thermosensitive ferromagnetic implant with low Curie temperature (FILCT). The FILCT was then coated with gold (Au-FILCT) to improve its heating efficiency for treating the human body. However, part of the magnetic field was shielded due to the conductive gold coating, thereby decreasing the possibility of our orientable pickup coil system for contactless temperature sensing based on the linearity between magnetic induction and implant temperature around the Curie point. As an alternative approach to the gold coating of FILCT, this paper examined a mixture of FILCT and a high heating-efficient magnetic nanofluid (Resovist) subjected to a magnetic field (f = 500 kHz, H = 4.95 kA/m). As a result, the change in magnetic induction detected caused by the mixture is enhanced compared to that of Au-FILCT (1.9 times) and FILCT (1.3 times). Furthermore, the temperature rising rate of the mixture is 4.3 times faster than that of FILCT. The results obtained also suggest that for hyperthermia implant, the preferred volume fraction of magnetic nanoparticles is approximately 0.5%. We hypothesized that the magnetic nanoparticles (median core diameter d 0 = 3.6 nm) in Resovist fill the gaps between the magnetic microparticles (d 0 = 83.6 μm) in FILCT, thereby reducing the demagnetizing field of microparticles and causing its permeability to be improved.
Dumbbell-shaped hybrid nanoparticles, consisting of gold and iron oxide (Au-Fe3O4 NPs), show promise for magnetic hyperthermia cancer therapy. However, conventional synthesis methods using toxic iron pentacarbonyl (Fe(CO)5) raise safety concerns. We propose a safer approach using triiron dodecacarbonyl (Fe3(CO)12) as a precursor. We synthesize these NPs by initially reducing gold (III) chloride trihydrate with a tert-butylamine-borane complex at room temperature, yielding Au NPs. These Au NPs are combined with a Fe3(CO)12 solution and heated to 300 °C for 1 hour, resulting in the desired dumbbell-shaped Au-Fe3O4 NPs. Characterization confirms their morphology, with average sizes of 5 nm for Au NPs and 15 nm for Fe3O4 NPs. Our systematic evaluation of hydrophilic-treated Au-Fe3O4 NPs (Ms=49.5 emu/g at 3T, 300K) demonstrates temperature increases beyond the therapeutic threshold of 45 °C (ΔT=8 °C) at higher field strengths (8.6–30.0 kA/m), highlighting their cancer treatment potential. Quantitative analysis reveals superb performance, with a specific absorption rate (SAR) of 60.0 W/g and intrinsic loss power (ILP) of 0.25 nHm2kg−1 at the maximum field strength. These findings emphasize the significant potential of our dumbbell-shaped Au–Fe3O4 NPs for magnetic hyperthermia.
In this study, we experimentally demonstrated an ultrafast heating rate of ultrasmall gold-coated iron oxide magnetic nanoparticles (Fe 3 O 4 @Au NPs) by the ferromagnetic resonance (FMR) effect. Using the constructed setup, the ferromagnetic resonance and temperature increment of NPs under FMR were evaluated. The resonant frequency of Fe 3 O 4 @Au NPs and their uncoated Fe 3 O 4 NPs was several GHz and increased with increasing DC field strength. The resonant frequency of Fe 3 O 4 @Au NPs shifted slightly lower than that of Fe 3 O 4 NPs. The initial temperature rising rate reached the maximum values at their corresponding DC fields for FMR (e.g. 1.294 and 3.894 K/s under H DC =1200 Oe for RF field of f AC =4 GHz and H AC =4 Oe for Fe 3 O 4 @Au and Fe 3 O 4 NPs, respectively). These values were two orders of magnitude higher than that of Néel and the Brownian relaxation for the conventional magnetic hyperthermia. The maximum value also increased with increasing RF field frequency. The obtained results also indicate that it is possible to control the temperature of NPs by adjusting the parameters of the RF field and DC field, suggesting their potential use for therapeutic temperature control in magnetic hyperthermia applications.
We present the synthesis and characterization of ultrasmall iron oxide/gold composite nanoparticles (Fe3O4@Au NPs) with different Fe3O4 sizes, along with an evaluation of their heating efficiency for potential use in magnetic hyperthermia (MH) applications. The Fe3O4 NPs of approximately 5, 10, and 13 nm were synthesized using the thermal decomposition method, followed by gold deposition via the reduction of gold acetate at 190 °C. The morphology, structure, and magnetic properties of as-prepared Fe3O4 and their Fe3O4@Au NPs were determined and characterized by transmission electron microscope (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and vibrating sample magnetometer (VSM) analyses. The magnetization of Fe3O4 NPs increased with increasing their size, reaching 74.7 emu/g for ~13 nm NPs. The Fe3O4@Au NPs contained 94.3%, 96.3%, and 77.0% Au (wt%) for Fe3O4~5, Fe3O4~10, and Fe3O4~13 nm@Au, respectively, estimated from the magnetization values. The heating efficiency specific absorption rate (SAR) demonstrated an increasing trend with Fe3O4 size, reaching maximum values of 136.7 and 23.4 W/g under a magnetic field of 25.7 kA/m and 267 kHz for Fe3O4~13 nm and Fe3O4~13 nm@Au NPs, respectively. These results indicate high heating efficient capabilities and the potential use of NPs for MH applications.
In this study, we prepared ultrasmall FeCo nanoparticles (NPs) with a high magnetic moment and examined their antigen-antibody reaction for biodetection applications. The FeCo NPs were collected from the FeCo-BaF2 nanogranular film with Fe:Co:Ba:F = 14:11:21:54 at.%, by dissolving the film in water since the BaF2 matrix was deliquescent. The size of FeCo NPs was ∼5 nm and the saturation magnetization was estimated to be ∼15.30 kG (149.0 emu/g). The Candida albicans antibodies (abcam ab53891)-conjugated FeCo NPs were collected by using an ultracentrifugal separation (110 000 rpm, 90 min), they were then reacted with Candida albicans. The obtained result indicates that Candida albicans were absorbed successfully onto FeCo NPs, and the number of Candida albicans bound to FeCo NPs counted from the micrographs of the aggregates of FeCo NPs and Candida albicans increased significantly by adding sonication treatment of the film in water before binding them to the antibodies. The success of antigen-antibody reaction of ultrasmall NPs with high magnetic moment improves detection sensitivity as well as offers potential detection for smaller biomolecules.
A highly sensitive microstrip-line-type probe using a flexible substrate was developed to measure thin-film permeability continuously up to the millimeter-wave frequency range (over 30 GHz). The probe enables broad bandwidth and highly sensitive permeability measurements without sample size limitations. The complex permeability of the CoFeB film (45 mm × 25 mm and 0.5 μm in thickness), CoNbZr film (25 mm × 25 mm and 3 nm in thickness), and nickel ferrite film (8 mm × 5 mm, and 1.2 μm in thickness) were optimized. The measured permeability spectrum and ferromagnetic resonance frequency showed good agreement with the theoretical values based on the Landau-Lifshitz-Gilbert equation and eddy current generation up to 67 GHz.
