Agglomeration Of Magnetic Nanoparticles Research Articles

Magnetic biocomposite scaffold based on decellularized tendon ECM and MNP-deposited halloysite nanotubes: physicochemical, thermal, rheological, mechanical and in vitro biological evaluations

The development of new three-dimensional biomaterials with advanced versatile properties is critical to the success of tissue engineering (TE) applications. Here, (a) bioactive decellularized tendon extracellular matrix (dECM) with a sol-gel transition feature at physiological temperature, (b) halloysite nanotubes (HNT) with known mechanical properties and bioactivity, and (c) magnetic nanoparticles (MNP) with superparamagnetic and osteogenic properties were combined to develop a new scaffold that could be used in prospective bone TE applications. Deposition of MNPs on HNTs resulted in magnetic nanostructures without agglomeration of MNPs. A completely cell-free, collagen- and glycosaminoglycan- rich dECM was obtained and characterized. dECM-based scaffolds incorporated with 1%, 2% and 4% MNP-HNT were analysed for their physical, chemical, and in vitro biological properties. Fourier-transform infrared spectroscopy, x-ray powder diffractometry and vibrating sample magnetometry analyses confirmed the presence of dECM, HNT and MNP in all scaffold types. The capacity to form apatite layer upon incubation in simulated body fluid revealed that dECM-MNP-HNT is a bioactive material. Combining dECM with MNP-HNT improved the thermal stability and compressive strength of the macroporous scaffolds upto 2% MNP-HNT. In vitro cytotoxicity and hemolysis experiments showed that the scaffolds were essentially biocompatible. Human bone marrow mesenchymal stem cells adhered and proliferated well on the macroporous constructs containing 1% and 2% MNP-HNT; and remained metabolically active for at least 21 d in vitro. Collectively, the findings support the idea that magnetic nanocomposite dECM scaffolds containing MNP-HNT could be a potential template for TE applications.

Tailored nanoparticles for magnetic hyperthermia: Highly stable aqueous dispersion of Mn-substituted magnetite superparamagnetic nanoparticles by double surfactant coating for improved heating efficiency

This study presents a significant advancement in cancer therapy through the application of Mn-substituted magnetite superparamagnetic (SPM) nanoparticles, highlighting the potential of magnetic fluid hyperthermia (MFH) as an effective modality. However, its clinical applications have been limited by challenges such as low heating performance, agglomeration of magnetic nanoparticles (MNPs) in blood veins, and cytotoxicity. To address these crucial issues, surface engineered MNPs were synthesised by adopting a reverse micelles-based co-precipitation approach that effectively overcomes MNP agglomeration, ensuring uniform dispersion of the nanoparticles. Through careful optimization of Mn ion substitution within magnetite, we have achieved a significant enhancement in the heating performance of the magnetite SPM nanoparticles. The substitution of Mn2+ ions in magnetite has notably increased the specific absorption rate (SAR) value, as evidenced by a remarkable 181% increase (SAR: 510 kW/kg) obtained using the Box Lucas Method. This enhancement can be attributed to the elevated saturation magnetization resulting from the appropriate cation distribution within the MNPs. Furthermore, the increase in spin relaxation time with higher Mn concentration also contributes to the improvement in SAR values as MNPs retain their magnetic moments for an extended period before relaxing, leading to enhanced energy dissipation and higher SAR values. The hemolysis assays demonstrated minimal hemolysis rates (<5%) when exposed to red blood cells (RBCs), confirming the high biocompatibility of the MNPs. Additionally, MTT assays revealed excellent cytocompatibility (>90% cell viability) for Human Embryonic Kidney (HEK-293) cells across all compositions, further affirming the potential of these MNPs for clinical treatments. Overall, this study unveils a sustainable approach for cancer therapy using Mn-substituted magnetite SPM nanoparticles. Their remarkable heating performance and excellent biocompatibility make them promising for clinical applications in MFH.

A threefold increase in SAR performance for magnetic hyperthermia by compositional tuning in zinc-substituted iron oxide superparamagnetic nanoparticles with superior biocompatibility

In this work, we report a ultrahigh specific absorption rate (SAR) performance in Zn-substituted magnetite superparamagnetic (SPM) nanoparticles (NPs) for potential application in magnetic hyperthermia (MHT)-based cancer treatment. Although MHT shows promise in cancer therapy, challenges such as low heating performance, agglomeration of magnetic nanoparticles (MNPs) in blood veins, cytotoxicity, and hemocompatibility have hindered clinical uses. To overcome these challenges, we adopted a reverse-micelles based coprecipitation synthesis approach to prevent MNPs agglomeration and optimized the substitution of Zn ions in magnetite to enhance heating performance. Calorimetric measurements showed SAR values of 118 W/g and 181 W/g for magnetite NPs using the initial slope method (ISM) and Box Lucas method (BLM), respectively. Through our compositional optimizations, we achieved a significant increase in SAR value by consciously substituting Zn2+ ions in the magnetite lattice. Specifically, we obtained SAR values of 325 W/g and 579 W/g (>300% increase) for Zn0.3Fe2.7O4 MNPs using ISM and BLM, respectively. This enhancement can be attributed to improved saturation magnetization (174–257 kA/m) and magneto-crystalline anisotropy (12–24 kJ/m3). The increase in saturation magnetization in the magnetite MNPs can be explained by the higher magnetic moment resulting from increased Zn concentration up to ZnxFe3-xO4(x = 0.3), strengthening the JAB interaction. However, further increases in Zn concentration lead to a decrease in saturation magnetization due to non-collinearity, as described by the Yafet-Kittle model. Our optimized MNPs exhibit improved heating performance, enabling the use of lower MNPs concentrations for cancer treatment, reducing potential toxicity effects. Biocompatibility investigations demonstrated a low hemolysis rate (<5%) in a hemolysis assay with red blood cells and high cytocompatibility (>92% cell viability) in MTT assays for all compositions, confirming their potential suitability for clinical applications. This study offers a promising approach to enhance SAR performance, addressing MHT-based cancer treatment challenges, and improving clinical suitability.

Multi‐Interfaces Regulated Polyaniline/Nano‐Fe3O4/Graphene Ternary Hybrids for Ultra‐Broadband Electromagnetic Absorption

AbstractGraphene‐based electromagnetic absorbing materials have attracted growing attention, due to their great absorption efficiency and light weight. One common design principle is to load magnetic particles onto graphene. However, the agglomeration of magnetic nanoparticles on the graphene sheets limits further improvement in their electromagnetic absorption performances. In this work, polyaniline/nano‐Fe3O4/graphene ternary hybrids with regulated multi‐interfaces are designed by simply adjusting the adding order of graphene. The dispersion of nano‐Fe3O4 on graphene and the interactions among the ternary interfaces are synchronously controlled, which are considered to be the key factors restricting the hybrids’ performances. The polyaniline/nano‐Fe3O4/graphene ternary composites show ultra‐broadband electromagnetic absorption, with the optimal reflection loss peak reaching −57.2 dB at 11.4 GHz, and the effective bandwidth achieves 13.2 GHz, covering 4.8–18 GHz. It is found that the well dispersion of nano‐Fe3O4 can enhance the overall ferromagnetism and magnetic losses, while the modulation of the multi‐interfaces can further ameliorate the interfacial and dipole polarization, synergistically making the ultra‐broadband electromagnetic absorption. This work provides areferencing path for the design of subsequent multi‐interfacing electromagnetic absorbing materials.

Magnetic extraction of calcium oxalate crystals with iron oxide nanoparticles

Abstract Residual fragments can remain after kidney stone extraction which may necessitate another intervention. Magnetic nanoparticles (MNP) can be applied due to their properties of being able to bind to residual fragments and to be extracted by an external magnetic field. Calcium oxalate crystals and magnetic nanoparticles have been synthesized, characterized and used for binding and magnetic separation studies. The separation is validated by simulation and experimentally. MNP bind covalently to the fractals and a magnetic extraction of calcium oxalate fractals is possible. The agglomeration of MNP can be induced with the addition of salt which improves the extraction process. This proof-of-concept study is the fundament for a new way of stone extraction and can pave the way for new procedures in urology.

A seed germination-inspired interface polarization augmentation strategy toward superior electromagnetic absorption performance

Dielectric/magnetic composites are considered as attractive candidates for high-performance electromagnetic wave absorption (EMA) materials. However, the agglomeration of magnetic nanoparticles (NPs) in the carbon matrix is an unavoidable problem. The homogeneous interfaces caused by magnetic agglomeration are often detrimental to the reinforcement of interfacial polarization. Herein, inspired by seed germination process, a high temperature derived carbon nanotube method was employed to prevent the agglomeration issue of magnetic NiCo alloy NPs. With the significant proliferation of heterogeneous interfaces due to the separation between NiCo alloy NPs, the interfacial polarization is significantly reinforced. Besides, the graphitized carbon obtained by high temperature carbonization is responsible for the conductive loss. As a consequence, the NiCo alloy@N doping carbon nanosheets (NiCo@NCS) composites illustrated a strong EM attenuation ability compared to the composites with magnetic NiCo alloy NPs agglomeration. Finally, the minimum reflection loss (RLmin) was −61.4 dB and widest absorption bandwidth (fmax) reached 4.72 GHz at 2.0 mm and 2.1 mm, respectively. This seed germination-inspired approach can be a significant and efficient reference to prevent the agglomeration of magnetic NPs in dielectric/magnetic composites.

Efficient removal of Pb(II)/Cu(II) from aqueous samples by a guanidine-functionalized SBA-15/Fe3O4

A mesoporous guanidine functionalized Santa Barbara Amorphous-15(SBA-15)/Fe3O4 magnetic nanoadsorbent (Fe3O4@SBA-15-Gd) was prepared for decontamination of aqueous solutions from Pb(II) and Cu(II) heavy metals. The multistep fabrication route, including hydrothermal SBA-15 synthesis process, in situ magnetization by Fe3O4 magnetic nanoparticles (MNPs) (Fe3O4@SBA-15), post-synthetic method for composites’ modification by 3-aminopropyltriethoxysilane (APTES) (Fe3O4@SBA-15-NH2), and nucleophilic addition to cyanimide to prepare the magnetic Fe3O4@SBA-15-Gd nanoadsorbent was conducted. Moreover, the mesoporous SBA-15 was utilized to support Fe3O4 to diminish the MNPs agglomeration, and the guanidine functional group played a significant role in heavy metal adsorption. Various analyzing approaches were applied to validate the precise structure procedure. The novel adsorbent structure owes to the formation of bidentate chelating agent, guanidine groups, on the mesoporous SBA-15 support through a facile nucleophilic addition. An enhanced adsorption capability was acquired in this study. Hence, the Cu(II) and Pb(II) maximum adsorption capacity in optimized conditions reached ca. 344.82 mg/g and 303.03 mg/g. The obtained spherical-shaped MNPs in Fe3O4@SBA-15-Gd magnetic mesoporous nanoadsorbent presented average particles size ascertained to be ca. 63 nm. The Fe3O4@SBA-15-Gd nanoadsorbent rendered high porosity, high surface area, and abundant adsorption sites fabricated by cost-effective and accessible substance materials. Furthermore, the Freundlich model has explained the adsorption process, and the pseudo-second-order model describes the adsorption kinetics. The Fe3O4@SBA-15-Gd adsorbent was conveniently separated by an external magnet and regenerated three times without a notable decline in adsorption efficiency. Therefore, the prepared magnetic mesoporous nanoadsorbent is a privileged material for heavy metal elimination since it achieved remarkable adsorption capacity, yet more selectivity toward Cu(II) and Pb(II) adsorption via binding to the adsorbent’s chelating groups, and consequently, enhanced heavy metal ion amount decontamination.

Long-Term Clearance and Biodistribution of Magnetic Nanoparticles Assessed by AC Biosusceptometry.

Once administered in an organism, the physiological parameters of magnetic nanoparticles (MNPs) must be addressed, as well as their possible interactions and retention and elimination profiles. Alternating current biosusceptometry (ACB) is a biomagnetic detection system used to detect and quantify MNPs. The aims of this study were to evaluate the biodistribution and clearance of MNPs profiles through long-time in vivo analysis and determine the elimination time carried out by the association between the ACB system and MnFe2O4 nanoparticles. The liver, lung, spleen, kidneys, and heart and a blood sample were collected for biodistribution analysis and, for elimination analysis, and over 60 days. During the period analyzed, the animal’s feces were also collectedd. It was possible to notice a higher uptake by the liver and the spleen due to their characteristics of retention and uptake. In 60 days, we observed an absence of MNPs in the spleen and a significant decay in the liver. We also determined the MNPs’ half-life through the liver and the spleen elimination. The data indicated a concentration decay profile over the 60 days, which suggests that, in addition to elimination via feces, there is an endogenous mechanism of metabolization or possible agglomeration of MNPs, resulting in loss of ACB signal intensity.

Adsorption behavior and mechanism of As(V) on magnetic Fe3O4-graphene oxide (GO) nanohybrid composite material.

In this study, the magnetic Fe3O4-graphene oxide (GO) nanohybrid composite material was prepared via the combination of the modified Hummer's method and coprecipitation. The morphology of the hybrid sample showed that the diffusion of Fe3O4 nanoparticles into the porous channels of mesoporous GO layers not only restricted the restacking of GO nanosheets but also prevented the leaching and agglomeration of magnetic nanoparticles. The result of the kinetic and isotherm studies that were performed to evaluate the adsorption mechanism showed a good fit with the pseudo-second-order kinetic and Langmuir isotherm models. The As(V) adsorption efficiency, H, of the GO/Fe3O4 nanohybrid composite material reached the maximum value of 99.37% after 60min. The maximum adsorption capacity qm of the GO/Fe3O4 nanohybrid material was 14.1mg·g-1 in an acidic aqueous solution (pH 1). The role and contribution of GO and Fe3O4 nanoparticles in adsorption and the improvement in As(V) adsorption efficiency were also investigated in further detail. The findings of this work suggested that the GO/Fe3O4 nanohybrid material could be widely applied for polluted water treatment.

Assessing hyperthermia performance of hybrid textile filaments: The impact of different heating agents

The application of advanced textile materials functionalized with magnetic nanoparticles (MNP) has become increasingly important in tumor therapy. In this regard, the incorporation of MNP into polymeric filaments, so-called hybrid filaments, enables the development of magnetic heatable stents that, once implanted, are used to deliver therapeutic heat to the tumor site under the influence of an external alternating magnetic field (AMF). In this study, we investigate the hyperthermia performance of different hybrid filaments functionalized with MNP and discuss the relevant parameters influencing the heating efficiency such as MNP immobilization, agglomeration and magnetization as well as AMF settings. For this, three different MNP types (self-synthesized single domain MNP and two commercially available multi-domain MNP, BAYFERROX® and BNF-Starch) were incorporated in polypropylene filaments by melt spinning. Their heating efficiency was assessed in dependence of the AMF amplitude. Because of the blocking of Brownian rotation and bigger effective anisotropy constant caused by MNP agglomeration inside the filaments, the heating efficiency of all hybrid filaments was smaller than that of the corresponding MNP dispersed in water. Nevertheless, in all cases the heating efficiency increased with magnetic field amplitude. The highest specific loss power (SLP) values were reached for the self-synthesized particles at lower magnetic field amplitudes (<25 kA/m) and for BNF-Starch particles at high magnetic field amplitudes (>25 kA/m). This is caused by the higher anisotropy constant of the BNF-Starch particles and their collective magnetic response at higher magnetic field amplitudes.

Investigation of magnetically driven passage of magnetic nanoparticles through eye tissues for magnetic drug targeting

This paper elucidates the feasibility of magnetic drug targeting to the eye by using magnetic nanoparticles (MNPs) to which pharmaceutical drugs can be linked. Numerical simulations revealed that a magnetic field gradient of 20 T m−1 seems to be promising for dragging magnetic multicore nanoparticles of about 50 nm into the eye. Thus, a targeting magnet system made of superconducting magnets with a magnetic field gradient at the eye of about 20 T m−1 was simulated. For the proof-of-concept tissue experiments presented here the required magnetic field gradient of 20 T m−1 was realized by a permanent magnet array. MNPs with an optimized multicore structure were selected for this application by evaluating their stability against agglomeration of MNPs with different coatings in water for injections, physiological sodium chloride solution and biological media such as artificial tear fluid. From these investigations, starch turned out to be the most promising coating material because of its stability in saline fluids due to its steric stabilization mechanism. To evaluate the passage of MNPs through the sclera and cornea of the eye tissues of domestic pigs (Sus scrofa domesticus), a three-dimensionally printed setup consisting of two chambers (reservoir and target chamber) separated by the eye tissue was developed. With the permanent magnet array emulating the magnetic field gradient of the superconducting setup, experiments on magnetically driven transport of the MNPs from the reservoir chamber into the target chamber via the tissue were performed. The resulting concentration of MNPs in the target chamber was determined by means of quantitative magnetic particle spectroscopy. It was found that none of the tested particles passed the cornea, but starch-coated particles could pass the sclera at a rate of about 5 ng mm−2 within 24 h. These results open the door for future magnetic drug targeting to the eye.

Dual Size-Dependent Effect of Fe₃O₄ Magnetic Nanoparticles Upon Interaction with Lysozyme Amyloid Fibrils: Disintegration and Adsorption.

Nanomedicine compounds containing nanoparticles, such as iron oxides and gold, have been demonstrated to be effective in promoting different magnitudes of interaction with amyloid fibrils, of which disintegrating or inhibiting effects are of great importance to treating fibrillary aggregation-induced neurological disorders such as Alzheimer’s disease. This research herein studies the interaction between lysozyme amyloid fibrils, a type of fibers derived from hen egg white lysozyme, and Fe3O4 magnetic nanoparticles (MNPs) of an assorted diameter sizes of 5 nm, 10 nm and 20 nm, using atomic force microscopy (AFM). Specifically, the effects of the sizes of negatively charged MNPs on the resultant amyloid fibrillary mixture was investigated. Our results of AFM images indicated that the interaction between MNPs and the fibrils commences immediately after adding MNPs to the fibril solution, and the actions of such MNPs-doped fibrillary interplay, either integration or segmentation, is strongly dependent on the size and volume concentration of MNPs. In the cases of 5 nm and 20 nm particles of equivalent volume concentration, the adsorption and agglomeration of MNPs onto the fibrillary surfaces was observed, whereas, interestingly, MNPs with diameter size of 10 nm enables segmentation of the slender fibrils into debris when a proper implemented volume concentration was found, which signifies utter destruction of the amyloid fibrillary structure.

Enhanced removal and detection of benzo[a]pyrene in environmental water samples using carbon dots-modified magnetic nanocomposites

Magnetic nanoparticles (MNPs) have already proven their efficacy in the disposal of a wide array of environmental contaminants in recent years. However, the difficulties in dispersibility and agglomeration of MNPs arising from its own physical and chemical properties limit its large-scale application. Herein, we fabricated the carbon dots/fatty acid-coated MNPs (CDs/C11-Fe3O4) through a facile and simple method. To utilize the advantage of carbon dots, these limitations can be mitigated by diminishing the size of MNPs and modifying the surface of MNPs. Detailed characterization including VSM, FT-IR, XPS and TEM conformed that the higher adsorption capacity of CDs/C11-Fe3O4 is mainly attributed to low average size (<8 nm), which is obviously lower than that of C11-Fe3O4 (about 13 nm). The CDs/C11-Fe3O4 showed higher adsorption performance than that of C11-Fe3O4 nanocomposites (76.23 ng mg−1 for CDs/C11-Fe3O4 and 59.89 ng mg−1 for C11-Fe3O4). The adsorption processes of BaP on both C11-Fe3O4 and CDs/C11-Fe3O4 nanocomposites are exothermic, and well simulated by pseudo-second-order model. Moreover, the CDs/C11-Fe3O4 were also applied for the detection of BaP in large-volume water samples, which satisfies the China environmental protection standard, are promising candidates for water remediation.

Magnetic Thermometer: Thermal effect on the Agglomeration of Magnetic Nanoparticles by Magnetic field

We have investigated the agglomeration of magnetite nanoparticles in the aqueous solution under magnetic field by measuring temporal change of magnetic weight. The magnetic weight corresponds to the force due to the magnetization of magnetic materials. Superparamagnetic magnetite nanoparticles are synthesized and used in this work. When the aqueous solution of magnetite nanoparticle is placed under magnetic field, the magnetic weight of the sample jumps instantaneously by Neel and Brown mechanisms and thereafter increases steadily following a stretched exponential function as the nanoparticles agglomerate, which results from the distribution of energy barriers involved in the dynamics. Thermal motions of nanoparticles in the agglomerate perturb the ordered structure of the agglomerate to reduce the magnetic weight. Fluctuation of the structural order of the agglomerate by temperature change is much faster than the formation of agglomerate and explained well with the Boltzmann distribution, which suggests that the magnetic weight of the agglomerate works as a magnetic thermometer.

Multilayered inorganic-organic microdisks as ideal carriers for high magnetothermal actuation: assembling ferrimagnetic nanoparticles devoid of dipolar interactions.

The two major limitations for nanoparticle based magnetic hyperthermia in theranostics are the delivery of a sufficient number of magnetic nanoparticles (MNPs) with high heating power to specific target cells and the residence time of the MNPs at the target location. Ferromagnetic or Ferrimagnetic single domain nanoparticles (F-MNPs), with a permanent magnetic dipole, produce larger magnetic and thermal responses than superparamagnetic nanoparticles (SP-MNPs) but also agglomerate more. MNP agglomeration degrades their heating potential due to dipolar interaction effects and interferes with specific targeting. Additionally, MNPs bound to cells are often endocytosed by the cells or, in vivo, cleared out by the immune system via uptake in macrophages. Here, we present a versatile approach to engineer inorganic-polymeric microdisks, loaded with biomolecules, fluorophores and Fe3O4 F-MNPs that solves both challenges. These microdisks deliver the F-MNPs efficiently, while controlling any undesirable agglomeration and dipolar interaction, while also rendering the F-MNPs endocytosis resistant. We show that these micro-devices are suitable carriers to transport a flat assembly of F-MNPs to the cell membrane unchanged, preserving the magnetic response of the MNPs in any biological environment. The F-MNPs concentration per microdisk and degree of MNP interaction are tunable. We demonstrate that the local heat generated in microdisks is proportional to the surface density of F-MNPs when attached to the cell membrane. The key innovation in the production of these microdisks is the fabrication of a mushroom-shaped photolithographic template that enables easy assembly of the inorganic film, polymeric multilayers, and MNP cargo while permitting highly efficient lift-off of the completed microdisks. During the harvesting of the flat microdisks, the supporting mushroom-shaped templates are sacrificed. These resulting magnetic hybrid microdisks are tunable and efficient devices for magnetothermal actuation and hyperthermia.

Magnetic Relaxation of Agglomerated and Immobilized Iron Oxide Nanoparticles for Hyperthermia and Imaging Applications

Magnetic nanoparticles (MNPs) are used as therapeutic and diagnostic agents for local delivery of heat and image contrast enhancement in diseased tissue. Besides magnetization, the most important parameter that determines their performance for these applications is their magnetic relaxation, which can be affected when MNPs immobilize and agglomerate inside tissues. In this letter, we investigate different MNP agglomeration states for their magnetic relaxation properties under excitation in alternating fields and relate this to their heating efficiency and imaging properties. With focus on magnetic fluid hyperthermia, two different trends in MNP heating efficiency are measured: an increase by up to 23% for agglomerated MNP in suspension and a decrease by up to 28% for mixed states of agglomerated and immobilized MNP, which indicates that immobilization is the dominant effect. The same comparatively moderate effects are obtained for the signal amplitude in magnetic particle spectroscopy.

Agglomeration of magnetic nanoparticles and its effects on magnetic hyperthermia

Abstract Magnetic fluid hyperthermia (MFH) is a promising approach for organ-confined tumor treatment. In MFH, magnetic nanoparticles (MNP) are magnetically targeted at the tumor site and heated in an alternating magnetic field. The heat produced by the MNP is used to cause tumor cell death. At the tumor site, MNP bind to the cell membrane and form agglomerates before they are internalized into the intracellular compartments. Intracellular immobilization and the formation of agglomerates influence heating properties of MNP making it difficult to control the local heating inside the tumor. In this study, we investigated MNP agglomerated samples for their heating efficiency. We found an increase in heating of 22 % upon agglomeration. If MNP are additionally immobilized, however, the heating decreases by 30 %. Consequently, due to the binding of bigger MNP agglomerates at cellular level, heating efficiency inside tumors is assumed to decrease.

Surface functionalized LSMO nanoparticles with improved colloidal stability for hyperthermia applications

LSMO (La0.7Sr0.3MnO3) magnetic nanoparticles (MNPs) coated with double layer oleic acid (OA) surfactant are prepared to make a water based magnetic nanofluid for hyperthermia application. Various experimental techniques are used for bilayer coating analysis. The effect of the bilayer coating on magnetic properties is studied by superconducting quantum interface device (SQUID). Colloidal behaviour of coated MNPs in aqueous medium is studied by the zeta potential and dynamic light scattering. The effects of pH and ionic strength on the colloidal stability of the MNPs are studied in detail. For the bilayer-coated LSMO MNPs aggregation is not observed even in high ionic strength and at physiological pH (7.4). For making the nanofluid of the bilayer-coated MNPs the colloidal stability is studied in physiological media like phosphate buffer solution. Under induction heating experiment, hyperthermia temperature (42–43 °C) could be achieved by the bilayer-coated sample at a magnetic field of 168–335 Oe and frequency of 267 kHz. The bilayer OA coating can hinder the agglomeration of MNPs significantly and produce stable suspension with improved hyperthermia properties. The bilayer OA coating also improves the specific absorption rate (SAR) of LSMO MNPs from 25 to 40 W g−1.

Estimation of the size distribution of magnetic nanoparticles using modified magnetization curves

We herein describe several practical improvements to the method of obtaining the size distribution of magnetic nanoparticles (MNPs) using the magnetization curves obtained from a water-based MNP sample. A vibration sample magnetometer (VSM) was used in place of a superconducting quantum interference device (SQUID), to reduce MNP agglomeration and sedimentation by means of vibration during the measurements. A signal preprocessing method using background rejection was applied to improve the measurement technique for lower concentrations of water-based MNPs, because of the significance of the diamagnetic effect of water in dilute solutions. We further present the results of detailed studies using singular value decomposition (SVD) and the Tikhonov-regulated SVD method to reconstruct the size distribution of the original sample. The experiments show that the controlled use of SVD produces consistent results. Artificial oscillation found using both SVD and the Tikhonov-SVD methods indicates that the characterization of MNP using a magnetization curve could be subject to an upper limit to its accuracy for measuring size distribution.

Fast and Sensitive Measurement of Specific Antigen-Antibody Binding Reactions With Magnetic Nanoparticles and HTS SQUID

We have developed an HTS SQUID system for both time and frequency domain measurements of magnetic signals from the Brownian relaxation of liquid-suspended magnetic nanoparticles (MNPs) coated with antibodies. A planar YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7-x</sub> dc SQUID gradiometer with a baseline of 3 mm allows stable operation of the measurement system in an unshielded environment. Agglomeration of MNPs induced by prostate specific antigen-antibody binding complexes is characterized with our system and benchmarked with frequency domain measurements performed by Imego AB using an induction coil magnetometer. We estimate an upper bound for our immunoassay analyte sensitivity of 1.8 ng/radicHz.