Magnetic nanoparticles as heat-generating nanosources in hyperthermia treatment are still faced with many drawbacks for achieving sufficient clinical potential. In this context, increase in heating ...ability of magnetic nanoparticles in a biologically safe alternating magnetic field and also approach to a precise control on temperature rise are two challenging subjects so that a significant part of researchers’ efforts has been devoted to them. Since a deep understanding of Physics concepts of heat generation by magnetic nanoparticles is essential to develop hyperthermia as a cancer treatment with non-adverse side effects, this review focuses on different mechanisms responsible for heat dissipation in a radio frequency magnetic field. Moreover, particular attention is given to ferrite-based nanoparticles because of their suitability in radio frequency magnetic fields. Also, the key role of Curie temperature in suppressing undesired temperature rise is highlighted.
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•In MHT, the heat generated by MNPs is produced by independent mechanisms.•MHT demands MNPs with high heating efficiency in a safe alternating magnetic field.•Undesired temperature rise can be inhibited through Curie temperature of MNPs.•This review discusses about the Physics concepts involved in the above subjects.
We present a study on the magnetic behavior of dextran-coated magnetite nanoparticles (DM NPs) with sizes between 3 and 19 nm, synthesized by hydrothermal-assisted co-precipitation method. The ...decrease of saturation magnetization (
M
s
) with decreasing particle size has been modeled by assuming the existence of a spin-disordered layer at the particle surface, which is magnetically dead. Based on this core–shell model and taking into account the weight contribution of non-magnetic coating layer (dextran) to the whole magnetization, the dead layer thickness (
t
) and saturation magnetization
M
s
of the magnetic cores in our samples were estimated to be
t
=
6.8 Å and
M
s
=
98.8
emu
/
g
, respectively. The data of
M
s
were analyzed using a law of approach to saturation, indicating an increase in effective magnetic anisotropy (
K
eff
) with decreasing the particle size as expected from the increased surface/volume ratio in small MNPs. The obtained
K
eff
values were successfully modeled by including an extra contribution of dipolar interactions due to the formation of chain-like clusters of MNPs. The surface magnetic anisotropy (
K
s
) was estimated to be about
K
s
=
1.04
×
10
5
J
/
m
3
. Our method provides a simple and accurate way to obtain the
M
s
core values in surface-disordered MNPs, a relevant parameter required for magnetic modeling in many applications.
Graphical abstract
Folate-targeted iron oxide nanoparticles (FA@Fe
O
NPs) were prepared by a one-pot hydrothermal method and then used as cancer theranostic agents by combining magnetic resonance imaging (MRI) and ...magnetic hyperthermia therapy (MHT). Crystal structure, morphology, magnetic properties, surface functional group, and heating efficacy of the synthesized nanoparticles were characterized by XRD, TEM, VSM, FTIR, and hyperthermia analyses. The results indicated that the crystal structure, magnetic properties, and heating efficacy of the magnetite nanoparticles were improved by hydrothermal treatment. Toxicity of the prepared NPs was assessed in vitro and in vivo on the mammary cells and BALB/c mice, respectively. The results of the in vitro toxicity analysis showed that the FA@Fe
O
NPs are relatively safe even at high concentrations of the NPs up to 1000 µg mL
. Also, the targetability of the FA@Fe
O
NPs for the detection of folate over-expressed cancer cells was evaluated in an animal model of breast tumor using MRI analysis. It was observed that T
-weighted magnetic resonance signal intensity was decreased with the three-time injection of the FA@Fe
O
NPs with 24 h interval at a safe dose (50 mg kg
), indicating the accumulation and retention of the NPs within the tumor tissues. Moreover, the therapeutic efficacy of the MHT using the FA@Fe
O
NPs was evaluated in vivo in breast tumor-bearing mice. Hyperthermia treatment was carried out under a safe alternating magnetic field permissible for magnetic hyperthermia treatment (f = 150 kHz, H = 12.5 mT). The therapeutic effects of the MHT were evaluated by monitoring the tumor volume during the treatment period. The results showed that the mice in the control group experienced an almost 3.5-fold increase in the tumor volume during 15 days, while, the mice in the MHT group had a mild increase in the tumor volume (1.8-fold) within the same period (P < 0.05). These outcomes give promise that FA@Fe
O
NPs can be used as theranostic agents for the MRI and MHT applications.
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•A facile one-pot hydrothermal method was presented for preparation of hyaluronic acid-coated Fe3O4 nanoparticles.•Uptake of the Fe3O4@HA NPs by MDA-MB-231 cells was found to be ...4-fold higher than the normal cells.•The ILP value for Fe3O4@HA NPs was about 3.5 nHm2/kg, which is about 25-fold larger than that of obtained for Feridex.
In the present study, a facile one-pot hydrothermal method is introduced for preparation of hyaluronic acid-coated Fe3O4 nanoparticles (Fe3O4@HA NPs) for theranostic applications. In the proposed method, hyaluronic acid acts simultaneously as a biocompatible coating layer and as a targeting ligand for CD44 receptor overexpressed on the surface of breast cancer cells. The obtained product with narrow hydrodynamic size distribution exhibited a high colloidal stability at physiological pH for more than three months. Cytotoxicity measurements indicated a negligible toxicity of the prepared sample against L929 normal cells. Preferential targeting of Fe3O4@HA NPs to CD44-overexpressing cancer cells was studied by comparing the uptake of the prepared nanoparticles by MDA-MB-231 cancer cells (positive CD44 expression) and L929 normal cells (negative CD44 expression). Uptake of the Fe3O4@HA NPs by MDA-MB-231 cells was found to be 4-fold higher than the normal cells. Also, the in vitro analysis showed that, the uptake of Fe3O4@HA NPs by MDA-MB-231 breast cancer cells is significantly enhanced as compared to non-targeted dextran-coated Fe3O4 NPs. Moreover, the heat generation capability of the Fe3O4@HA NPs for magnetic hyperthermia application was studied by exposing the prepared nanoparticles to different safe alternating magnetic fields (f = 120 kHz, H = 8, 10, and 12 kA/m). The intrinsic loss power obtained for Fe3O4@HA NPs was about 3.5 nHm2/kg, which is about 25-fold larger than that of obtained for commercial available Fe3O4 nanoparticles for biomedical applications. Good colloidal stability, biocompatibility, high heating efficacy, and targeting specificity to CD44 receptor‐overexpressing cancer cells could make the Fe3O4@HA NPs as a promising multifunctional platform for diagnosis and therapeutic applications.
•Magnetite nanorods (MNRs) were synthesized using a one-pot solvothermal method.•The MNRs showed high SAR values in both magnetic hyperthermia and photothermia.•The MNRs have an excellent potential ...to be used as dual-responsive heating agents in thermal treatment.
The development of the multi-functional nanostructures has recently been of particular interest in therapeutic research for various diseases including atherosclerosis, cancer, etc. Indeed, the use of multi-responsive nanostructures that can remotely be activated by different stimuli is a promising strategy to combine the advantages of standalone methods and overcome their intrinsic drawbacks. In this regard, thermal treatment using heat-generating magnetic nanostructures that can remotely respond to a wide range of electromagnetic stimuli is of especial importance, mainly applied through magnetic hyperthermia therapy (MHT) and photothermal therapy (PTT) modalities. In this work, magnetite (Fe3O4) nanorods (MNRs) were synthesized using a one-pot solvothermal process. Adjusting the amount of hexadecylamine capping ligand and the filling percentage of the autoclave, uniformed-sized MNRs of 4·46nm in diameter and 31·09nm in length were prepared and investigated in terms of their heat-generating ability for application in the MHT and PTT. The experimental results show the good heat-generating ability of the MNRs in both modalities with the maximum absorption rate (SAR) values of 228.51 W/g (MHT) and 56.59 W/g (PTT).
•Heating efficiency of superparamagnetic NPs strongly depends on their size.•Optimization of particle size significantly increases the specific absorption rate of MNPs.•MNPs with average size of ...19 nm have an excellent potential ability in heat generation for application in MFH.
Dextran-coated magnetite (Fe3O4) nanoparticles with average particle sizes of 4 and 19 nm were synthesized through in situ and semi-two-step co-precipitation methods, respectively. The experimental results confirm the formation of pure phase of magnetite as well as the presence of dextran layer on the surface of modified magnetite nanoparticles. The results also reveal that both samples have the superparamagnetic behavior. Furthermore, calorimetric measurements show that the dextran-coated Fe3O4 nanoparticles with an average size of 4 nm cannot produce any appreciable heat under a biologically safe alternating magnetic field used in hyperthermia therapy; whereas, the larger ones (average size of 19 nm) are able to increase the temperature of their surrounding medium up to above therapeutic range. In addition, measured specific absorption rate (SAR) values confirm that magnetite nanoparticles with an average size of 19 nm are very excellent candidates for application in magnetic hyperthermia therapy.
Finding the interrelation among the magnetic response of the heat mediators to an alternating magnetic field (AMF) and other relevant parameters in magnetic hyperthermia therapy (MHT) can give the ...possibility to accurately design high-performance nanostructured magnetic nanoparticles (MNPs). In this context, the present work investigates the effect of the zinc substitution on magnetic properties and heat-generating ability of poly vinyl alcohol-coated Zn-substituted cobalt ferrite nanoparticles (PZC NPs) with different zinc contents (ZnxCo1−xFe2O4; x = 0, 0.15, 0.3, 0.4, 0.5, 0.7), synthesized using hydrothermal-assisted co-precipitation method. The obtained results showed that the PZC NPs with an average particle size ∼ 15 nm exhibit ferrimagnetic features and their coercivity (Hc) values decrease as the zinc content (x) increases. Moreover, as Zn2+ replaces Co2+ in the structure, saturation magnetization (Ms) increases up to about 52 emu/g for PZC-30 NPs (x =0.3) and then decreases for higher Zn contents. The hyperthermia measurements were performed at a fixed filed frequency (f=120kHz) and different magnetic field strengths (Happl=17,20,24.5kA/m). The results revealed that, as x increases, specific absorption rate (SAR) at each Happl first shows an increasing trend and then reaching a maximum value (at x=0.4) follows a decreasing trend. Moreover, the highest SAR (25.25 W/g) belongs to the magnetic fluid containing PZC-40 NPs at Happl=24.5kA/m. Furthermore, the Happl-dependency of the SAR values were obtained as a power law (SAR∼Happln) in which the exponent n rises as x decreases, suggesting that the optimal composition tends to shift to ones with the lower x at higher Happl. The obtained results, revealing the high impact of the interrelation between the chemical composition and the Happl on the MNPs heating efficiency, can shed more light on the way to design heat mediators with optimal performance through simultaneous control of the chemical composition and the Happl.
A precise control of the particle size of dextran-coated magnetite nanoparticles (Dex-M NPs) was successfully performed by combination of co-precipitation and hydrothermal synthesis methods. The ...Dex-M NPs, in the size range 3.1–18.9 nm, were used to fabricate biocompatible magnetic fluids for application in magnetic hyperthermia therapy (MHT). The effects of the carrier fluid viscosity, particle size, and applied magnetic field strength (Happl) on the specific loss power (SLP) of the Dex-M NPs were investigated at a fixed magnetic field frequency (f). The experimental results show that SLP of the larger Dex-M NPs significantly decreases for a highly viscous carrier fluid. Moreover, regardless of the carrier fluid viscosity, the particle size strongly affects the heating efficiency of the Dex-M NPs. SLP ranges from zero for the smallest Dex-M NPs (with particle size d = 3.1 nm) to 55.21 W/g for the largest ones (d = 18.9 nm) at Happl = 28 kA/m and f = 120 kHz. The most important finding in our research is that, at a fixed frequency, the optimal size of the Dex-M NPs (the size that maximizes SLP) shows a rising trend by enhancing Happl. In fact, the highest values of SLP at Happl = 11 kA/m, 13 − 17.5 kA/m, and 19 − 28 kA/m are obtained for the Dex-M NPs with d = 11.5 nm, 15 nm, and 18.9 nm, respectively. The shift of optimal size to the higher values by increasing Happl could shed light on the correlated effects of the particle size and Happl on the heating efficiency of magnetic nanoparticles (MNPs) and pave a new way toward the better tuning of them for an effective and biologically safe treatment.
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•Dex-M NPs with size range 3.1 to 18.9 nm were synthesized.•Effects of the particle size, fluid viscosity and Happl on SLP were investigated.•The optimal size for maximizing SLP shows a rising trend by enhancing Happl.•This result opens a new avenue for understanding correlated effects of the particle size and Happl on SLP.
Biocompatible ferrofluids based on dextran coated iron oxide nanoparticles were fabricated by conventional co-precipitation method. The experimental results show that the presence of dextran in ...reaction medium not only causes to the appearance of superparamagnetic behavior but also results in significant suppression in saturation magnetization of dextran coated samples. These results can be attributed to size reduction originated from the role of dextran as a surfactant. Moreover, weight ratio of dextran to magnetic nanoparticles has a remarkable influence on size and magnetic properties of nanoparticles, so that the sample prepared with a higher weight ratio of dextran to nanoparticles has the smaller size and saturation magnetization compare with the other samples. In addition, the ferrofluids containing such nanoparticles have an excellent stability at physiological pH for several months. Furthermore, the biocompatibility studies reveal that surface modification of nanoparticles by dextran dramatically decreases the cytotoxicity of bare nanoparticles and consequently improves their potential application for diagnostic and therapeutic purposes.
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•In situ surface modification of magnetite NPs significantly decreases their size and saturation magnetization.•The effect of size shrinkage in dextran coated NPs results in the appearance of superparamagnetic property.•Dextran coated magnetite NPs have the more biocompatibility compared with the bare counterparts.•The ferrofluids prepared with a higher weight ratio of dextran to NPs are highly stable at physiological pH.
We present a study on the magnetic behavior of dextran-coated magnetite nanoparticles (DM NPs) with sizes between 3 and 19 nm, synthesized by hydrothermal-assisted co-precipitation method. The ...decrease of saturation magnetization (\(M_s\)) with decreasing particle size has been modeled by assuming the existence of a spin-disordered layer at the particle surface, which is magnetically dead. Based on this core-shell model and taking into account the weight contribution of the non-magnetic coating layer (dextran) to the whole magnetization, the dead layer thickness (\(t\)) and saturation magnetization \(M_s\) of the magnetic cores in our samples were estimated to be \(t = 6.8~\mathrmÅ\) and \(M_s = 98.8~\mathrm{emu/g}\), respectively. The data of \(M_s\) were analyzed using a law of approach to saturation, indicating an increase in effective magnetic anisotropy (\(K_{eff}\)) with decreasing particle size as expected from the increased surface/volume ratio in small MNPs. The obtained \(K_{eff}\) values were successfully modeled by including an extra contribution of dipolar interactions due to the formation of chain-like clusters of MNPs. The surface magnetic anisotropy (\(K_s\)) was estimated to be about \(K_s = 1.04\times10^5~\mathrm{J/m^3}\). Our method provides a simple and accurate way to obtain the \(M_s\) core values in surface-disordered MNPs, a relevant parameter required for magnetic modeling in many applications.
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