Nanoarchitectonics of PEG-Coated Ni-Zn Ferrite Nanoparticles and Mechanical Analysis of Heat Generation by Magnetic Relaxation

The magnetic relaxation of magnetic nanoparticles (MNPs) has been used as a potential heating agent for magnetic hyperthermia treatment (MHT). This requires an understanding of the heating mechanism of MNPs, such as Néel relaxation; however, few studies about magnetic relaxation using a low-frequency AC magnetic field have been reported. This study attempts to clarify the correlation between the dominance of Néel relaxation in low-frequency AC fields and the magnetic properties. Nanoparticles of Ni_0.8Zn_0.2Fe₂O₄ coated with poly(ethylene glycol) (PEG) were synthesized in various sizes (d?=?12, 15, and 19 nm), and were subjected to structural analysis, PEG modification, and magnetic measurements. The PEG400 coating results in a hydrodynamic diameter ten times smaller than that of our previous sample. The heat generation experiment was conducted on samples suspended in solvents of different viscosities in the presence of an AC field (h?=?3.2 kAm^?1, f?=?90 kHz). The specific absorption rate (SAR) as a function of the viscosity of the 15-nm NP sample is consistent with the theoretically calculated value in cases where the Néel relaxation is dominant. Therefore, we conclude that the Néel relaxation dominates the heating mechanism of the 15 nm sample. Rather than being fully superparamagnetic, this sample was partly superparamagnetic and slightly ferromagnetic, with the dominance of the Néel relaxation to a certain degree affected by spin blocking. Detailed analysis of the magnetic relaxation is crucial to improve the heating efficiency of MNPs for MHT.

     

Anti-neoplastic Applications of Heparin Coated Magnetic Nanoparticles Against Human Ovarian Cancer

This study determines the effect of bare and heparin (HP)-based magnetic iron oxide (Fe₃O₄) nanoparticles (MNPs) on the human ovarian cancer cells of CP70 type. Cisplatin (CP) was used as the anticancer drug, entrapped in MNPs. The nanoparticles containing the anticancer drug, CP, were prepared by a solvent evaporation and emulsification cross-linking method. The physicochemical properties of the nanoparticles were characterized by various techniques, and uniform particles of bare and HP coated MNPs, with average particle sizes of 25 and 45 ± 15 nm, having high encapsulation efficiencies, were obtained. Additionally, a sustained release of CP from the MNPs was successful in vitro. Cytotoxicity tests showed that the MNP–HP–CP had higher cell toxicity than the individual HP; and confocal microscopic analysis confirmed excellent cellular uptake efficiency of CP70 cells for MNP–HP–CP. These results indicate that HP based MNPs have potential uses as anticancer drug carriers and have also proved to have enhanced anti-neoplastic effects.     

Chemical Synthesis of Monodisperse Magnetic Nanoparticles for Sensitive Cancer Detection

This short tutorial review highlights the advance in high temperature solution phase chemical synthesis of monodisperse magnetic nanoparticles (MNPs), especially iron oxide NPs, as contrast enhancement agents for cancer detection by magnetic resonance imaging (MRI). It introduces briefly the unique nanomagnetism of MNPs required for MRI. It then summarizes some typical methods used to prepare monodisperse Fe₃O₄ and ferrite MFe₂O₄ MNPs from high temperature organic phase reaction with controlled magnetic properties. It further outlines the chemistry used to make these MNPs biocompatible and target-specific. Finally it presents two examples to demonstrate the MNP control achieved from chemical synthesis for sensitive detection of cancer.     

Cytotoxic effect of functionalized superparamagnetic samarium doped iron oxide nanoparticles for hyperthermia application

Magnetic Fluid Hyperthermia (MFH) is an emerging and safe technique for cancer treatment. Radiotherapy and Chemotherapy are widely adopted techniques for treating cancer but cause damage to the nearby healthy tissue. This paves the way for hyperthermia treatment for cancer. Since healthy cells are more heat-tolerant than malignant cells, magnetic nanoparticles with superparamagnetic properties were used in hyperthermia treatment. Surface modified magnetite (Fe₃O₄) iron oxide nanoparticles with enhanced stability, solubility, bio-compatibility and magnetic property were employed in hyperthermia treatment. In the present study, Superparamagnetic Samarium doped magnetite (Fe₃O₄:Sm) nanoparticles were functionalized with Oleylamine (OAm) and polyvinyl alcohol (PVA) by the sol-gel process. The obtained nanoparticles were characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Transmission Electron Microscopy (TEM), and UV–Visible diffuse reflectance spectroscopy (UV-DRS), Thermogravimetric analysis (TGA) and Vibrating Sample Magnetometer (VSM). From XRD data, the crystallite size of oleylamine coated samarium doped magnetite (OAm–Fe₃O₄:Sm) and PVA-coated samarium doped Fe₃O₄ (PVA- Fe₃O₄:Sm) were found to be 9.5 nm and 10.9 nm, respectively. TEM images of the functionalized nanoparticles were visualized as a spherical structure with reduced agglomeration. UV-DRS gives the bandgap value of OAm–Fe₃O₄:Sm and PVA- Fe₃O₄:Sm coated samarium doped magnetite to be 2.3 eV and 2 eV respectively. VSM measurement of OAm-Fe₃O₄:Sm and PVA- Fe₃O₄:Sm coated, showed superparamagnetic behaviour. The cytotoxicity study on the L929 cell line shows that both oleylamine and PVA-coated samarium doped magnetite were less toxic and biocompatible compared to the uncoated Fe₃O₄:Sm. The hyperthermia study reveals a rise in temperature within a few seconds with a high Specific Absorption Rate (SAR) value, confirming that the functionalized Samarium doped Fe₃O₄ was an effective nanomaterial for hyperthermia application.     

Interforce initiated by magnetic nanoparticles for reducing internal concentration polarization in CTA forward osmosis membrane

The interforce between the magnetic composite forward osmosis (FO) membranes and the magnetic draw solution was proposed to reduce the internal concentration polarization (ICP) of FO process, and realized the synergetic permeability improvement of resultant FO membranes. The key factor was the successful fabrication of the Fe₃O₄ magnetic nanoparticles (MNPs) with small‐size and narrow distribution via co‐precipitation method. The cellulose triacetate (CTA) magnetic composite FO membranes were fabricated using Fe₃O₄ as additive via in situ interfacial polymerization, and named CTA‐Fe₃O₄. Dynamic light scattering (DLS) and zeta results showed that the coated sodium oleate on the MNPs explained their reducing aggregation and the stability of various pHs. The MNPs' surface segregation during demixing process resulted in the improvement of hydrophilicity, Fe content and roughness of resultant CTA‐Fe₃O₄ composite FO membranes. Furthermore, the in situ interfacial polymerization resulted in the formation of the polyamide selective layer, and the CTA‐Fe₃O₄ membrane's N content was 11.02% to 11.12%. The permeability properties (FO and pressure retarded osmosis modules) were characterized using 1.0M NaCl and 100 mg/L Fe₃O₄ as draw solutions, respectively. The results indicated that the higher concentration of MNPs supplied more interforce and better FO permeability properties. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44852.     

Nanoparticles Functionalised with Re(I) Tricarbonyl Complexes for Cancer Theranostics

Globally, cancer is the second (to cardiovascular diseases) leading cause of death. Regardless of various efforts (i.e., finance, research, and workforce) to advance novel cancer theranostics (diagnosis and therapy), there have been few successful attempts towards ongoing clinical treatment options as a result of the complications posed by cancerous tumors. In recent years, the application of magnetic nanomedicine as theranostic devices has garnered enormous attention in cancer treatment research. Magnetic nanoparticles (MNPs) are capable of tuning the magnetic field in their environment, which positively impacts theranostic applications in nanomedicine significantly. MNPs are utilized as contrasting agents for cancer diagnosis, molecular imaging, hyperfusion region visualization, and T cell-based radiotherapy because of their interesting features of small size, high reactive surface area, target ability to cells, and functionalization capability. Radiolabelling of NPs is a powerful diagnostic approach in nuclear medicine imaging and therapy. The use of luminescent radioactive rhenium(I), ^188/186Re, tricarbonyl complexes functionalised with magnetite Fe₃O₄ NPs in nanomedicine has improved the diagnosis and therapy of cancer tumors. This is because the combination of Re(I) with MNPs can improve low distribution and cell penetration into deeper tissues.     

Radioiodinated Magnetic Nanoparticles Conjugated With Moxifloxacin: Synthesis and In Vitro Biological Affinities

Magnetic nanoparticles (MNPs) were synthesized and coated with tetraethyl orthosilicate and aminosilane to create functional amino groups. Moxifloxacin (MXF) was conjugated to the modified MNPs using glutaraldehyde as crosslinker. Finally, MXF conjugated magnetic nanoparticles were radiolabeled and their biological affinities such as cell incorporation ratio, cytotoxicity, and their potential as cell imaging probe were investigated using A-549 cells.     

Synthesis of MIL-Modified Fe3O4 Magnetic Nanoparticles for Enhancing Uptake and Efficiency of Temozolomide in Glioblastoma Treatment

A nanometric hybrid system consisting of a Fe₃O₄ magnetic nanoparticles modified through the growth of Fe-based Metal-organic frameworks of the MIL (Materials Institute Lavoiser) was developed. The obtained system retains both the nanometer dimensions and the magnetic properties of the Fe₃O₄ nanoparticles and possesses increased the loading capability due to the highly porous Fe-MIL. It was tested to load, carry and release temozolomide (TMZ) for the treatment of glioblastoma multiforme one of the most aggressive and deadly human cancers. The chemical characterization of the hybrid system was performed through various complementary techniques: X-ray-diffraction, thermogravimetric analysis, FT-IR and X-ray photoelectron spectroscopies. The nanomaterial showed low toxicity and an increased adsorption capacity compared to bare Fe₃O₄ magnetic nanoparticles (MNPs). It can load about 12 mg/g of TMZ and carry the drug into A172 cells without degradation. Our experimental data confirm that, after 48 h of treatment, the TMZ-loaded hybrid nanoparticles (15 and 20 μg/mL) suppressed human glioblastoma cell viability much more effectively than the free drug. Finally, we found that the internalization of the MIL-modified system is more evident than bare MNPs at all the used concentrations both in the cytoplasm and in the nucleus suggesting that it can be capable of overcoming the blood-brain barrier and targeting brain tumors. In conclusion, these results indicate that this combined nanoparticle represents a highly promising drug delivery system for TMZ targeting into cancer cells.     

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.     

Novel polyurethane rigid foam/organically modified iron oxide nanocomposites

Magnetic polyurethane rigid foam nanocomposites were synthesized by incorporation of surface functionalized iron oxide nanoparticles with 3‐aminopropyltriethoxysilane (APTS). Magnetite nanoparticles (MNPs) and Fe₃O₄@APTS were synthesized via co‐precipitation and sol–gel methods, respectively. The main purpose of the surface modification of MNPs was the formation of hydrogen bond between amino groups of Fe₃O₄@APTS with the urethane groups to improve magnetic and thermal properties of the nanocomposites. The effect of different amounts of Fe₃O₄@APTS on the thermal and magnetic behavior of resultant nanocomposite was investigated and the optimum percentage of nanostructure in foam formulation was defined. POLYM. COMPOS., 38:877–883, 2017. © 2015 Society of Plastics Engineers     

Facile and efficient synthesis of magnetic fluorescent nanocomposites based on carbon nanotubes

Multifunctional nanomaterials composed of magnetic and fluorescent nanoparticles have been one of the most extensive pursuits because of the potential application in bio-research. In this paper, we demonstrated an efficient method by coupling CdSe/CdS/ZnS quantum dots (QDs) with Fe₃O₄ magnetic nanoparticles(MNPs) while functionalized multiwall carbon nanotubes (f-MWCNTs) were used as matrix to synthesize a kind of magnetic fluorescent nanocomposite. Compared with other matrix materials, carbon nanotubes have the advantages of high surface areas and good biocompatibility. The incorporation of f-MWCNTs supplies plenty of nucleation sites for the preferential growth of Fe₃O₄ nanoparticles, avoiding the agglomeration phenomenon of Fe₃O₄ MNPs in traditional co-precipitation method. Moreover, the un-reacted functional groups of f-MCNTs can further adsorb biological species and drugs, averting the decline of fluorescent intensity caused by the modification of biological species and drugs. The synthetic product maintains the unique properties of rapid magnetic response and efficient fluorescence, which shows a broad application prospect in fluorescent labeling, biological imaging, cell tracking and drug delivery.     

Preparation, characterization and application of bilayer surfactant-stabilized ferrofluids

Fe₃O₄ magnetic nanoparticles (MNPs) were prepared by the coprecipitation of Fe²⁺ and Fe³⁺ using ammonium hydroxide (NH₄OH) as precipitating agent. Transmission electronic microscopy (TEM) showed that the particle-size is around 10 nm. X-ray powder diffraction (XRD) indicated the sole existence of inverse cubic spinel phase of Fe₃O₄. The surface of MNPs was coated with oleate sodium as the primary layer and polyethylene glycol 4000 (PEG-4000) as the secondary layer to improve the stability of water-based ferrofluids (FFs). The dosages of oleate sodium and PEG-4000 were found to have an important effect on increasing the solid content. Gouy magnetic balance showed that the saturation magnetization could be as high as 1.44 × 10⁵ A/m. Laser particle-size analyzer determined the aggregate size in FFs. The Fe₃O₄ MNPs did not change through the preparation of FFs. Differential scanning calorimetry-thermogravimetry (DSC-TG) and Fourier transform infrared spectroscopy (FT-IR) analysis showed existence of two distinct surfactants on the particle surface. The concentrated and diluted FFs were characterized by UV-vis spectrophotometer and excellent stability was found. The rheological measurements indicated that viscosity increased with the increase of solid content and applied magnetic field, but decreased with the increase of temperature. The FFs showed the non-Newtonian behavior of shear-thinning when the solid content was high. The mechanical properties of polyvinylalcohol (PVA) thin film can be greatly improved by adding FFs.     

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.     

Study on Maximum Specific Loss Power in Fe3O4 Nanoparticles Decorated with Biocompatible Gamma-Cyclodextrins for Cancer Therapy with Superparamagnetic Hyperthermia

Different chemical agents are used for the biocompatibility and/or functionality of the nanoparticles used in magnetic hyperthermia to reduce or even eliminate cellular toxicity and to limit the interaction between them (van der Waals and magnetic dipolar interactions), with highly beneficial effects on the efficiency of magnetic hyperthermia in cancer therapy. In this paper we propose an innovative strategy for the biocompatibility of these nanoparticles using gamma-cyclodextrins (γ-CDs) to decorate the surface of magnetite (Fe₃O₄) nanoparticles. The influence of the biocompatible organic layer of cyclodextrins, from the surface of Fe₃O₄ ferrimagnetic nanoparticles, on the maximum specific loss power in superparamagnetic hyperthermia, is presented and analyzed in detail in this paper. Furthermore, our study shows the optimum conditions in which the magnetic nanoparticles covered with gamma-cyclodextrin (Fe₃O₄–γ-CDs) can be utilized in superparamagnetic hyperthermia for an alternative cancer therapy with higher efficiency in destroying tumoral cells and eliminating cellular toxicity.     

Hydrothermal synthesis of magnetite nanoparticles as MRI contrast agents

Magnetite (Fe₃O₄) nanoparticles prepared using hydrothermal approach were employed to study their potential application as magnetic resonance imaging (MRI) contrast agent. The hydrothermal process involves precursors FeCl₂·4H₂O and FeCl₃ with NaOH as reducing agent to initiate the precipitation of Fe₃O₄, followed by hydrothermal treatment to produce nano-sized Fe₃O₄. Chitosan (CTS) was coated onto the surface of the as-prepared Fe₃O₄ nanoparticles to enhance its stability and biocompatible properties. The size distribution of the obtained Fe₃O₄ nanoparticles was examined using transmission electron microscopy (TEM). The cubic inverse spinel structure of Fe₃O₄ nanoparticles was confirmed by X-ray diffraction technique (XRD). Fourier transform infrared (FTIR) spectrum indicated the presence of the chitosan on the surface of the Fe₃O₄ nanoparticles. The superparamagnetic behaviour of the produced Fe₃O₄ nanoparticles at room temperature was elucidated using a vibrating sample magnetometer (VSM). From the result of custom made phantom study of magnetic resonance (MR) imaging, coated Fe₃O₄ nanoparticles have been proved to be a promising contrast enhanced agent in MR imaging.     

Biodegradable magnetic‐sensitive shape memory poly(ɛ‐caprolactone)/Fe3O4 nanocomposites

A novel biodegradable magnetic‐sensitive shape memory poly(?‐caprolactone) nanocomposites, which were crosslinked with functionalized Fe₃O₄ magnetic nanoparticles (MNPs), were synthesized via in situ polymerization method. Fe₃O₄ MNPs pretreated with γ‐(methacryloyloxy) propyl trimethoxy silane (KH570) were used as crosslinking agents. Because of the crosslinking of functionalized Fe₃O₄ MNPs with poly(?‐caprolactone) prepolymer, the properties of the nanocomposites with different content of functionalized Fe₃O₄ MNPs, especially the mechanical properties, were significantly improved. The nanocomposites also showed excellent shape memory properties in both 60 °C hot water and alternating magnetic field (f = 60, 90 kHz, H = 38.7, 59.8 kA m^?1). In hot water bath, all the samples had shape recovery rate (R_r) higher than 98% and shape fixed rate (R_f) nearly 100%. In alternating magnetic field, the R_r of composites was over 85% with the highest at 95.3%. In addition, the nanocomposites also have good biodegradability. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45652.     

A Novel Colorimetric Immunoassay Utilizing the Peroxidase Mimicking Activity of Magnetic Nanoparticles

A simple colorimetric immunoassay system, based on the peroxidase mimicking activity of Fe₃O₄ magnetic nanoparticles (MNPs), has been developed to detect clinically important antigenic molecules. MNPs with ca. 10 nm in diameter were synthesized and conjugated with specific antibodies against target molecules, such as rotaviruses and breast cancer cells. Conjugation of the MNPs with antibodies (MNP-Abs) enabled specific recognition of the corresponding target antigenic molecules through the generation of color signals arising from the colorimetric reaction between the selected peroxidase substrate, 3,3′,5,5′-tetramethylbenzidine (TMB) and H₂O₂. Based on the MNP-promoted colorimetric reaction, the target molecules were detected and quantified by measuring absorbance intensities corresponding to the oxidized form of TMB. Owing to the higher stabilities and economic feasibilities of MNPs as compared to horseradish peroxidase (HRP), the new colorimetric system employing MNP-Abs has the potential of serving as a potent immunoassay that should substitute for conventional HRP-based immunoassays. The strategy employed to develop the new methodology has the potential of being extended to the construction of simple diagnostic systems for a variety of biomolecules related to human cancers and infectious diseases, particularly in the realm of point-of-care applications.     

Synthesis of magnetic citric‐acid‐functionalized graphene oxide and its application in the removal of methylene blue from contaminated water

A magnetic nanocomposite of citric‐acid‐functionalized graphene oxide was prepared by an easy method. First, citric acid (CA) was covalently attached to acyl‐chloride‐functionalized graphene oxide (GO). Then, Fe₃O₄ magnetic nanoparticles (MNPs) were chemically deposited onto the resulting adsorbent. CA, as a good stabilizer for MNPs, was covalently attached to the GO; thus MNPs were adsorbed much more strongly to this framework and subsequent leaching decreased and less agglomeration occurred. The attachment of CA onto GO and the formation of the hybrid were confirmed by Fourier transform infrared spectroscopy, scanning electron microscopy, X‐ray diffraction spectrometry and transmission electron microscopy. The specific saturation magnetization of the magnetic CA‐grafted GO (GO‐CA‐Fe₃O₄) was 57.8 emu g^?1 and the average size of the nanoparticles was found to be 25 nm by transmission electron microscopy. The magnetic nanocomposite was employed as an adsorbent of methylene blue from contaminated water. The adsorption tests demonstrated that it took only 30 min to attain equilibrium. The adsorption capacity in the concentration range studied was 112 mg g^?1. The GO‐CA‐Fe₃O₄ nanocomposite was easily manipulated in an external magnetic field which eases the separation and leads to the removal of dyes. Thus the prepared nanocomposite has great potential in removing organic dyes. © 2014 Society of Chemical Industry     

Modification of Magnetite Cellulose Nanoparticles via Click Reaction for use in Controlled Drug Delivery

Superparamagnetic Fe₃O₄ nanoparticles (MNPs) were functionalized by modified cellulose. The modified cellulose was synthesized through bromoacetylation of cellulose (BACell) followed by the substitution of sodium azide to form BACell-N₃. The remaining methylene bromide groups on BACell-N₃ was further reacted with the MNPs to form Fe₃O₄/Cell-N₃. Then propargyl alcohol (PA) was immobilized on the azide-terminated Fe₃O₄ nanoparticles through copper (I)-catalyzed azide-alkyne cycloaddition (click reaction) to form Fe₃O₄/Cell/TAA nanoparticles. Doxorubicin (DOX) was loaded on prepared nanoparticles and release profiles of the DOX as a model drug from the Fe₃O₄/Cell/TAA nanoparticles and its loading capacity were determined by UV–Vis absorption at λ_max 483?nm.     

Continuous preparation of Fe3O4 nanoparticles combined with surface modification by L-cysteine and their application in heavy metal adsorption

L-cysteine functionalized Fe₃O₄ magnetic nanoparticles (Cys–Fe₃O₄ MNPs) were continuously fabricated by a simple high-gravity reactive precipitation method combined with surface modification through a novel impinging stream-rotating packed bed with the assistance of sonication. The obtained Cys–Fe₃O₄ MNPs was characterized by XRD, TEM, FTIR, TGA and VSM, and further used for the removal of heavy metal ions from aqueous solution. The influence of pH values, contact time and initial metal concentration on the adsorption efficiency were investigated. The results revealed that the adsorption of Pb(II) and Cd(II) were pH dependent process, and the pH 6.0 was found to be optimum condition. Moreover, the adsorption kinetic for Cys–Fe₃O₄ MNPs followed the mechanism of the pseudo-second order kinetic model, and their equilibrium data were fitted with the Langmuir isothermal model well. The maximum adsorption capacities calculated from Langmuir equation were 183.5 and 64.35 mg g⁻¹ for Pb(II) and Cd(II) at pH 6.0, respectively. Furthermore, the adsorption and regeneration experiment showed there was about 10% loss in the adsorption capacity of the as-prepared Cys–Fe₃O₄ MNPs for heavy metal ions after 5 times reuse. All the above results provided a potential method for continuously preparing recyclable adsorbent applied in removing toxic metal ions from wastewater through the technology of process intensification.