The cytotoxicity evaluation of magnetic iron oxide nanoparticles on human aortic endothelial cells

One major obstacle for successful application of nanoparticles in medicine is its potential nanotoxicity on the environment and human health. In this study, we evaluated the cytotoxicity effect of dimercaptosuccinic acid-coated iron oxide (DMSA-Fe₂O₃) using cultured human aortic endothelial cells (HAECs). Our results showed that DMSA-Fe₂O₃ in the culture medium could be absorbed into HAECs, and dispersed in the cytoplasm. The cytotoxicity effect of DMSA-Fe₂O₃ on HAECs was dose-dependent, and the concentrations no more than 0.02 mg/ml had little toxic effect which were revealed by tetrazolium dye assay. Meanwhile, the cell injury biomarker, lactate dehydrogenase, was not significantly higher than that from control cells (without DMSA-Fe₂O₃). However, the endocrine function for endothelin-1 and prostacyclin I-2, as well as the urea transporter function, was altered even without obvious evidence of cell injury in this context. We also showed by real-time PCR analysis that DMSA-Fe₂O₃ exposure resulted in differential effects on the expressions of pro- and anti-apoptosis genes of HAECs. Meanwhile, it was noted that DMSA-Fe₂O₃ exposure could activate the expression of genes related to oxidative stress and adhesion molecules, which suggested that inflammatory response might be evoked. Moreover, we demonstrated by in vitro endothelial tube formation that even a small amount of DMSA-Fe₂O₃ (0.01 and 0.02 mg/ml) could inhibit angiogenesis by the HAECs. Altogether, these results indicate that DMSA-Fe₂O₃ have some cytotoxicity that may cause side effects on normal endothelial cells.     

Morphological effect of oscillating magnetic nanoparticles in killing tumor cells

Forced oscillation of spherical and rod-shaped iron oxide magnetic nanoparticles (MNPs) via low-power and low-frequency alternating magnetic field (AMF) was firstly used to kill cancer cells in vitro. After being loaded by human cervical cancer cells line (HeLa) and then exposed to a 35-kHz AMF, MNPs mechanically damaged cell membranes and cytoplasm, decreasing the cell viability. It was found that the concentration and morphology of the MNPs significantly influenced the cell-killing efficiency of oscillating MNPs. In this preliminary study, when HeLa cells were pre-incubated with 100 μg/mL rod-shaped MNPs (rMNP, length of 200 ± 50 nm and diameter of 50 to 120 nm) for 20 h, MTT assay proved that the cell viability decreased by 30.9% after being exposed to AMF for 2 h, while the cell viability decreased by 11.7% if spherical MNPs (sMNP, diameter of 200 ± 50 nm) were used for investigation. Furthermore, the morphological effect of MNPs on cell viability was confirmed by trypan blue assay: 39.5% rMNP-loaded cells and 15.1% sMNP-loaded cells were stained after being exposed to AMF for 2 h. It was also interesting to find that killing tumor cells at either higher (500 μg/mL) or lower (20 μg/mL) concentration of MNPs was less efficient than that achieved at 100 μg/mL concentration. In conclusion, the relatively asymmetric morphological rod-shaped MNPs can kill cancer cells more effectively than spherical MNPs when being exposed to AMF by virtue of their mechanical oscillations.     

Synthesis,structural, magnetic and NO2 gas sensing property of CuO nanoparticles

Cupric oxide (CuO) nanoparticles are synthesized by the oxidation of Cu/Cu₂O, which is obtained by the chemical reduction of Cu²⁺ ions with ascorbic acid. XRD pattern confirmed the formation of CuO, and FE-SEM image shows the clusters consisting of 25–30 nm sized particles. The band gap energy (3.7 eV) from optical absorption spectra is blue shifted to that of bulk values. The Néel temperature, T_N ≈ 230 K for paramagnetic to antiferromagnetic transition was clearly seen. The magnetic hysteresis loops at 5 K showed weak ferromagnetic behavior. Based on the dc electrical conductivity (300–500 K), the apparent activation energy was 0.36 eV. The NO₂ gas sensing property of CuO was reasonably good in the temperature range of 200–300 °C, and the sensitivity increased with an increase in gas concentration but the effect of temperature is marginal.     

Structural,magnetic and electric properties of ZrO2 tapes decorated with magnetic nanoparticles

We produced ZrO₂ ceramic tape decorated with magnetic nanoparticles through tape casting technique. The green and sintered magnetic tapes were characterized by XRD, SEM, EDS, magnetic measurements, and I–V curves. We investigated the changes in the structural, magnetic and electrical properties, after the sintering process, and discussed the connections between them. The magnetic properties, performed in a wide range of external magnetic field and temperature, show magnetite phase for the magnetic nanoparticles governing the magnetic and electric properties of the green tape. On the other hand, for the sintered tape, the increase in the hematite phase led to remarkable changes in the magnetic and electrical properties. The electrical characterization reflects the observed changes in the structural properties after the sintering process. Additionally, the main advantages of the ceramic tapes decorated with magnetic nanoparticles reside in the possibility of producing functional thin ceramic materials that are easily moldable for electronic devices applications.     

Therapeutic effect of magnetic nanoparticles on calcium silicate bioceramic in alternating field for biomedical application

The cancerous bone may be treated using magnetite nanoparticles (MNPs) coupled with hyperthermia treatment technology. During the last three decades, calcium-silicate (CS) based bioceramics have been investigated as a proper choice due to their bioactivity, biocompatibility, magnetization property, and ability to form suitable apatite for hard tissue engineering approaches. For this purpose, three-dimensional bio-nanocomposite scaffolds utilizing bioactive wollastonite (WS) and bioglass (BG) as composed based materials with 0 wt% (S1), 5 wt% (S2), 10 wt% (S3), and 15 wt% (S4) of Zr–Fe₃O₄ are considered in this study. These materials with two various space-agents such as sodium chloride (NaCl) and sodium bicarbonate (NaHCO₃) particles containing ball mill with high energy and pressing under 150 MPa, and sintered at 850 °C are analyzed. Additionally, X-ray diffraction (XRD), scanning electron microscopy (SEM), vibrating-sample magnetometer (VSM), and mechanical tests include of toughness and compressive strength are investigated. The powder's and scaffold's crystals size are measured between 30 and 50 nm, and the pores and porosity size are measured from 70 to 180 μm and 25%–40%. The VSM curves illustrate that the zirconium-ferrite has a soft magnetic property, which is easily magnetized by applying a small amount of magnetic field, and it rapidly loses its magnetic moment by cutting off the field. The low coercive force, as well as high magnetic saturation with low residue, are represented for the S2 and S3. The obtained outcomes indicate that the best amounts of mechanical properties amongst the specimens are related to the specimen with 15 wt%, 7.9 ± 1 MPa of compressive strength, and 203.3 ± 10 MPa of elastic modulus. Likewise, the biological assessment shows that the sample containing 10 wt% MNPs provides a better apatite creation on porous scaffolds after 28 days. The gained outcomes represent that those specimens containing 10 and 15 wt% MNPs provide proper biological and mechanical replies.     

Effects of hydrothermal process parameters on the physical,magnetic and thermal properties of Zn0.3Fe2.7O4 nanoparticles for magnetic hyperthermia applications

Effects of hydrothermal temperature and time on physical, magnetic and thermal properties of Zn-substituted magnetite nanoparticles (Zn_0.3Fe_2.7O₄) were assessed. The magnetic nanoparticles were synthesized via citric acid-assisted hydrothermal reduction route at temperatures of 150, 175 and 200 °C for duration of 10, 15 and 20 h. The nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), vibrating sample magnetometer (VSM) and specific loss power (SLP) measurements. The results showed that temperature and time of the hydrothermal process both had significant effects on nanoparticles composition and properties. It was observed that at 150 °C, heat generation was insufficient to produce activation energy required for nucleation of Zn_0.3Fe_2.7O₄ spinel nanoparticles, even after a long time. At 175 °C, although temperature was low, but the suitable condition for nucleation of nanoparticles was made and spinel nanoparticles with the size of about 13 nm were formed after 15 h. Nonetheless, since crystallinity and SLP of the nanoparticles was low, they showed weak performance for magnetic hyperthermia. At 200 °C, the required activation energy was provided for nanoparticles nucleation; however, the spinel was oxidized to hematite, resulting in a decrease in thermal and magnetic properties. In overall, the nanoparticles synthesized at 200 °C for 15 h possessed the best characteristics of reasonable purity, saturation magnetization of about 35.9 emu/g and SLP of 18.7 W/g.     

Structural,magnetic, thermal and optical properties of Sn2+ cation doped magnetite nanoparticles

Tin doped nanomagnetites, Sn_xFe_3-xO₄, were synthesized with various concentrations of Sn²⁺ ion (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) by co-precipitation method. XRD, VSM, TG-DTA, SEM-EDX and UV–Vis were used to characterize and study the structural, magnetic, thermal, and optical properties of Sn_xFe_3-xO₄ nanoparticles. XRD confirmed the presence of cubic structure and spinel phase of tin doped magnetites. The d-spacing, lattice parameter, density, crystallite size and cation distribution were derived from the XRD analysis. The M − H curves exhibited changes in saturation magnetization (M_s), coercive field (H_c), remanent magnetization (M_r) and susceptibility (χ), with increasing concentration of non-magnetic Sn²⁺ ions. Differential thermal analysis was used to study the thermal stability of Sn_xFe_3-xO₄ nanoparticles. The SEM images revealed the surface morphology of the nanoparticles and the EDX spectra showed an increase in the Sn content and a corresponding decrease in the Fe content for the tin doped samples. The optical bandgap was found to be centered at 3.9 eV for the synthesized materials. This systematic study may be the first comprehensive report on synthesis and characterization of tin doped magnetites.     

Photocatalytic,magnetic, and electrochemical properties of La doped BiFeO3 nanoparticles

We successfully prepared La_1?xBi_xFeO₃ (L_xB_1?xFO, x?=?0.01–0.1) nanoparticles using a sol-gel technique, and studied their photocatalytic, magnetic, and electrochemical properties. Structural refinement studies of the prepared nanoparticles revealed a gradual structural transition from rhombohedral to orthorhombic. The average grain size was observed to decrease with increasing the concentration of La. The photocatalytic degradation of Rhodamine B (RhB) in the presence of the prepared nanoparticles was studied under visible light irradiation. The L_0.06B_0.94FO nanoparticles showed higher degradation efficiency compared to pure BiFeO₃ (BFO) nanoparticles. Magnetic studies showed that La doping improved the magnetization of BFO due to the reduction in grain size and destruction of cycloid coupling of spins. Higher specific capacitance values were obtained for La doped BFO (LBFO) nanoparticles compared to BFO nanoparticles. A maximum specific capacitance of 219?F?g^?1 was obtained at a current density of 1?A?g^?1 for LBFO nanoparticles.     

Preparation of novel magnetic nanoparticles as draw solutes in forward osmosis desalination

Novel magnetic nanoparticles (MNPs), Fe₃O₄@SiO₂ and Fe₃O₄@SiO₂@PEG-(COOH)₂, were prepared by loading different amounts of SiO₂ or/and PEG-(COOH)₂ onto Fe₃O₄ nanoparticles, and their feasibility to be used as forward osmosis (FO) draw solutes was investigated. The characterization of the materials showed that, compared to normal Fe₃O₄ nanoparticles, the modified MNPs exhibited enhanced dispersity and high osmotic pressure in aqueous solution. The FO experiment indicated that the synthesized draw solutes could obtain a water flux as high as 10 L·m^-2·h^-1 with an aquaporin FO membrane. The optimal concentration of the added tetraethyl orthosilicate was 30% during the synthesis. The novel MNPs could be easily recovered from draw solutions by magnetic field, and the recovery rate of Fe₃O₄@SiO₂ and Fe₃O₄@SiO₂@PEG-(COOH)₂ was 83.95% and 63.37%, respectively. Moreover, after 5 recycles of reuse, the water flux of Fe₃O₄@SiO₂ and Fe₃O₄@SiO₂@PEG-(COOH)₂ as draw solutes still remained 64.36% and 85.26%, respectively. The experimental results demonstrated that the synthesized core–shell magnetic nanoparticles are promising draw solutes, and the Fe₃O₄@SiO₂@PEG-(COOH)₂ was more suitable to be used as draw solute in FO process.     

Effect of lemon juice on microstructure,phase changes,and magnetic performance of CoFe2O4 nanoparticles and their use on release of anti-cancer drugs

Cobalt ferrite magnetic nanoparticles were synthesized and developed by a modified Pechini method using iron nitrate, cobalt nitrate, ethylene glycol (EG), and sucrose with different volumes of lemon juice (10, 20, 30, 40, 50, 60, and 70 ml) as the source of chelating agent as well as nonmagnetic elements such as Ca and Mg ions. The XRD patterns confirmed that all samples synthesized by different contents of extracted lemon juice had a cubic crystal structure with single-phase spinel. Scanning electron microscopy revealed that cobalt ferrite nanoparticles had a semi-spherical morphology. Also, the vibrating sample magnetometer indicated that the saturation magnetization of CoFe₂O₄ nanoparticles prepared with different values of extracted lemon juice increased from 18.6 emu/g for 10 ml extracted lemon juice to 75.7 emu/g for 50 ml extracted lemon juice, after which the saturation magnetization diminished. Afterwards, the CoFe₂O₄ nanoparticles were coated with polyethylene glycol (PEG) and doxorubicin (DOX) drugs, whereby drug delivery was detected at different pH levels. The CoFe₂O₄-PEG-DOX nanocomposite could release doxorubicin by more than 42% at pH = 5.4 in 75 h.     

The heating effect of iron-cobalt magnetic nanofluids in an alternating magnetic field: application in magnetic hyperthermia treatment

In this research, FeCo alloy magnetic nanofluids were prepared by reducing iron(III) chloride hexahydrate and cobalt(II) sulfate heptahydrate with sodium borohydride in a water/CTAB/hexanol reverse micelle system for application in magnetic hyperthermia treatment. X-ray diffraction, electron microscopy, selected area electron diffraction, and energy-dispersive analysis indicate the formation of bcc-structured iron-cobalt alloy. Magnetic property assessment of nanoparticles reveals that some samples are single-domain superparamagnetic, while others are single- or multi-domain ferromagnetic. The stability of the magnetic fluids was achieved by using a CTAB/1-butanol surfactant bilayer. Results of Gouy magnetic susceptibility balance experiments indicate good stability of FeCo nanoparticles even after dilution. The inductive properties of corresponding magnetic fluids including temperature rise and specific absorption rate were determined. Results show that with increasing of the nanoparticle size in the single-domain size regime, the generated heat increases, indicating the significant effect of the hysteresis loss. Finally, the central parameter controlling the specific absorption rate of nanoparticles was introduced, the experimental results were compared with those of the Stoner-Wohlfarth model and linear response theory, and the best sample for magnetic hyperthermia treatment was specified.     

Synthesis and magneto-structural properties of chitosan coated ultrafine cobalt ferrite nanoparticles for magnetic fluid hyperthermia in viscous medium

AC induction heating mediated magnetic fluid hyperthermia of superparamagnetic nanoparticles (MNPs) is being widely explored for localized thermo-therapy of tumours. One of the primary hindrances for rapid adaptation of this technique is the loss of heating efficiency when the MNPs are placed within the viscous tissue medium, which necessitates undesired increase in MNP concentrations or exposure time during practical applications. With an objective to mitigate this, here we report the viscosity independent magnetic hyperthermia properties of biocompatible ultrafine (average size ～ 2.5 nm) chitosan-coated superparamagnetic CoFe₂O₄ MNPs synthesized using a low-cost co-precipitation technique. The presence of the chitosan coating is confirmed from Fourier transform infrared and X-ray photoelectron spectroscopy. The superparamagnetic nature of the synthesized MNPs at 300 K is confirmed from Mössbauer spectroscopy, isothermal and temperature dependent magnetization studies. Experimental findings indicate a higher field-induced heating efficiency for the chitosan-coated MNPs due to superior colloidal stability. The ultrafine size, combined with higher anisotropy energy density, results in viscosity independent Nèel relaxation-dominated magneto-thermal energy conversion for the CoFe₂O₄ MNPs. Experimental results reveal negligible loss of heating efficiency due to partial abrogation of Brownian relaxation when the chitosan-coated MNPs are immobilized in a tissue-equivalent agar medium, which is beneficial for practical applications. The heating efficiency of ～72.1 ± 2.8 W/g_Fe (at 33.1 kA/m and 126 kHz), obtained in the present study for the chitosan-coated MNPs, is higher than the previously documented values for ultrafine CoFe₂O₄ MNPs, which is useful for reducing the exposure time during practical applications. Further, the chitosan coating rendered the ultrafine CoFe₂O₄ MNPs bio-compatible against L929 cell line. The satisfactory magnetic fluid hyperthermia efficiency, negligible room temperature coercivity, retention of the field-induced heating efficiency in tissue-equivalent agar medium due to Nèel-dominated relaxation dynamics and superior biocompatibility, make the chitosan-coated ultrafine CoFe₂O₄ MNPs an attractive candidate for practical MFH applications.     

Changes in the nanoparticle aggregation rate due to the additional effect of electrostatic and magnetic forces on mass transport coefficients

The need may arise to be able to simulate the migration of groundwater nanoparticles through the ground. Transportation velocities of nanoparticles are different from that of water and depend on many processes that occur during migration. Unstable nanoparticles, such as zero-valent iron nanoparticles, are especially slowed down by aggregation between them. The aggregation occurs when attracting forces outweigh repulsive forces between the particles. In the case of iron nanoparticles that are used for remediation, magnetic forces between particles contribute to attractive forces and nanoparticles aggregate rapidly. This paper describes the addition of attractive magnetic forces and repulsive electrostatic forces between particles (by ‘particle’, we mean both single nanoparticles and created aggregates) into a basic model of aggregation which is commonly used. This model is created on the basis of the flow of particles in the proximity of observed particles that gives the rate of aggregation of the observed particle. By using a limit distance that has been described in our previous work, the flow of particles around one particle is observed in larger spacing between the particles. Attractive magnetic forces between particles draw the particles into closer proximity and result in aggregation. This model fits more closely with rapid aggregation which occurs between magnetic nanoparticles.     

Preparation and characterization of PVA films with magnetic nanoparticles: The effect of particle loading on drug release behavior

This article deals with the drug release behavior of theophylline (Th) from poly(vinyl alcohol) (PVA) hydrogels, prepared with magnetic nanoparticles at different particle loadings. These biocompatible matrices were obtained by incorporating different amounts of an aqueous ferrofluid into PVA hydrogels, loaded with Th as a marker for drug‐delivery studies. PVA films with magnetic particles proved to be magnetic field‐responsive materials as the drug release decreased through the application of a relative low and uniform magnetic field for particle concentrations of 0.9% w/w or higher. Moreover, the percentage of restriction of drug release is found to be correlated with particle loading. The in vitro release profiles were analyzed by applying a semiempirical power law to obtain the kinetic parameters. The value of the release exponent was found to be in the range 0.54–0.56 in all experiments, which thus indicates a predominant diffusional mechanism for drug release from these smart magnetic hydrogels. This effect suggests the possibility of modulating the release behavior by controlling the particle content in the preparation of the composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The influence of cationic surfactant CTAB on optical,dielectric and magnetic properties of cobalt ferrite nanoparticles

In the present work, the influence of cationic surfactant CTAB (cetyltrimethylammonium bromide) on size, shape and coalescence behaviour of cobalt ferrite nanoparticles (CFNPs) synthesized via hydrothermal method is reported. Pure CFNPs show no additional peaks, whereas α-Fe₂O₃ phase is observed in CTAB added CFNPs upon annealing. FT-IR analysis confirms the formation of M − O vibrational bands (metal -oxygen) at tetrahedral A-site and octahedral B-site for both samples. SEM observations reveal less agglomeration and smaller particle size for surfactant added CFNPs. Raman spectral study confirms the formation of cubic spinel structure and Raman active modes of CTAB added CFNPs. UV–Vis spectra indicate a decrease in the energy band gap with annealing. The dielectric constant of surfactant added CFNPs decreases with increasing applied frequencies for both real and imaginary, but ac conductivity increases with increasing frequencies. Two sextet patterns of Fe³⁺ trivalent ions from tetrahedral and octahedral sites are observed in Mössbauer spectra. VSM study indicate the ferrimagnetic nature of CTAB added CFNPs. The electrochemical analysis reveals the pseudocapacitive nature of working electrode prepared by CTAB added CFNPs.     

The enhancement effect of gold nanoparticles in drug delivery and as biomarkers of drug-resistant cancer cells

The enhancement effect of 3-mercaptopropionic acid capped gold nanoparticles (NPs) in drug delivery and as biomarkers of drug-resistant cancer cells has been demonstrated through fluorescence microscopy and electrochemical studies. The results of cell viability experiments and confocal fluorescence microscopy studies illustrate that these functionalized Au NPs could play an important role in efficient drug delivery and biomarking of drug-resistant leukemia K562/ADM cells. This could be explored as a novel strategy to inhibit multidrug resistance in targeted tumor cells and as a sensitive method for the early diagnosis of certain cancers. Our observations also indicate that the interaction between the functionalized Au NPs and biologically active molecules on the surface of leukemia cells may contribute the observed enhancement in cellular drug uptake.     

The effect of the ethylene glycol to metal nitrate molar ratio on the phase evolution,morphology and magnetic properties of single phase BiFeO3 nanoparticles

In this work, single phase BiFeO₃ nanoparticles have been synthesized by thermal decomposition of a glyoxylate complex achieved by the redox reaction between ethylene glycol and nitrate anions. The effects of different molar ratios of ethylene glycol to metal nitrate anions on the phase evolution, morphology and magnetic properties were investigated by infrared spectroscopy, thermal analysis, X-ray diffraction, electron microscopy and vibrating sample magnetometry methods. The single phase bismuth ferrite nanoparticles synthesized with the ethylene glycol to nitrate anions molar ratio of 5 showed the weak ferromagnetism behavior with saturation magnetization of 1.3 emu/g, due to the size confinement effect. Furthermore, the BiFeO₃ nanoparticles were used for the degradation of methylene blue (MB) as a typical dye pollutant under direct sunlight irradiation.     

人肝细胞生长因子基因真核表达质粒的构建及其在人骨髓间充质干细胞中的表达

目的构建人肝细胞生长因子(Human hepatocyte growth factor,hHGF)真核表达质粒,并检测其在人骨髓间充质干细胞(Bone marrow mesenchymal stem cells,BMSCs)中的表达及其对细胞生长的影响。方法采用密度梯度法从人骨髓中分离BMSCs,流式细胞术检测细胞表型,成脂及成骨诱导其分化。PCR扩增hHGF基因,定向克隆至pEGFP-N1载体中,构建重组表达质粒pEGFP-N1-hHGF,通过电穿孔法转染BMSCs,荧光显微镜下观察增强型绿色荧光蛋白的表达,RT-PCR及Western blot法检测hHGF基因mRNA的转录及蛋白的表达,MTT法检测hHGF对BMSCs增殖活力的影响。结果 BMSCs高表达CD29和CD44,不表达CD34和CD45;BMSCs在体外有向成脂及成骨细胞诱导分化的能力。酶切及基因测序证实,重组表达质粒pEGFP-N1-hHGF构建正确;转染后48 h观察到转染细胞中有绿色荧光蛋白表达;RT-PCR法和Western blot检测到hHGF基因在BMSCs中表达;转染hHGF基因的BMSCs增殖活力明显高于空白对照组和空载体转染组(P<0.05)。结论成功构建了hHGF基因真核表达质粒,转染人BMSCs后获得表达,表达的hHGF可促进BMSCs增殖。     

Effect of the rare-earth substitution on the structural,magnetic and adsorption properties in cobalt ferrite nanoparticles

Rare-earth (RE) substituted cobalt ferrite CoFe_1.9RE_0.1O₄ (RE=Pr³⁺, Sm³⁺, Tb³⁺, Ho³⁺) nanoparticles are synthesized by a facile hydrothermal method without any template and surfactant. The effects of RE³⁺ substitution on structural, magnetic and adsorption properties of cobalt ferrite nanoparticles are investigated. Structure, morphology, particle size, chemical composition and magnetic properties of the ferrite nanoparticles are studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), high solution transmission electron microscopy (HRTEM), energy-dispersive spectrometer (EDS), Fourier transform spectroscopy (FTIR), Raman spectra and vibrating sample magnetometry (VSM). The results indicate that the as-synthesized samples have the pure spinel phase, uniform crystallite size and narrow particle size distribution. Meanwhile, the RE³⁺ substitution leads to the decrease in the particle size, magnetization and coercivity of the CoFe₂O₄ ferrite. Notably, it demonstrates that the RE³⁺ doping can apparently enhance the adsorption capacity for Congo red (CR) onto ferrite nanoparticles. Adsorption equilibrium studies show that adsorption of CR follows the Langmuir model. The monolayer adsorption capacities of CoFe_1.9Sm_0.1O₄ and CoFe_1.9Ho_0.1O₄ are 178.6 and 158.0 mg/g, respectively. The adsorption kinetics can be described by the pseudo-second-order model.     

Cytotoxic effects and the mechanism of three types of magnetic nanoparticles on human hepatoma BEL-7402 cells

The evaluation of the toxicity of magnetic nanoparticles (MNPs) has attracted much attention in recent years. The current study aimed to investigate the cytotoxic effects of Fe₃O₄, oleic acid-coated Fe₃O₄ (OA-Fe₃O₄), and carbon-coated Fe (C-Fe) nanoparticles on human hepatoma BEL-7402 cells and the mechanisms. WST-1 assay demonstrated that the cytotoxicity of three types of MNPs was in a dose-dependent manner. G1 (Fe₃O₄ and OA-Fe₃O₄) phase and G2 (C-Fe) phase cell arrests and apoptosis induced by MNPs were detected by flow cytometry analysis. The increase in apoptosis was accompanied with the Bax over-expression, mitochondrial membrane potential decrease, and the release of cytochrome C from mitochondria into cytosol. Moreover, apoptosis was further confirmed by morphological and biochemical hallmarks, such as swollen mitochondria with lysing cristae and caspase-3 activation. Our results revealed that certain concentrations of the three types of MNPs affect BEL-7402 cells viability via cell arrest and inducing apoptosis, and the MNPs-induced apoptosis is mediated through the mitochondrial-dependent pathway. The influence potency of MNPs observed in all experiments would be: C-Fe > Fe₃O₄ > OA-Fe₃O₄.