Microwave absorption by magnetic nanoparticles in organisms

An estimate of the rate of absorption of the electromagnetic microwaves by magnetic nanoparticles in organisms is presented. The absorption takes place due to the energy dissipation at the ferromagnetic resonance. Based on the known solution of the Landau-Lifshitz equation, the imaginary part of the complex magnetic susceptibility is evaluated that gives the absorption rate. It is shown that even in the conditions of thermal isolation of the particles, their temperature growth would be insignificant at absorption of the emission with the energy flux density of the order of 1 mW/cm2, and the given mechanism is unrelated to the observable effects of low-intensity microwaves.     

Microwave absorption by folded DNA chains

Absorption of radiation by DNA polymer is calculated for the case of bent polymer chains. The molecule is assumed to be straight except for localized bends. The region between two bends is studied in particular. The vibrational properties of the bends are parameterized by a transmission and a reflection coefficient. A general Green function expression for absorption is studied for various values of the damping rate, as well as the transmission/reflection coefficients. Curves of absorption vs frequency are shown for a number of cases.     

Hysteresis losses and specific absorption rate measurements in magnetic nanoparticles for hyperthermia applications

BackgroundMagnetic hysteresis loops areas and hyperthermia on magnetic nanoparticles have been studied with the aim of providing reliable and reproducible methods of measuring the specific absorption rate (SAR).MethodsThe SAR of Fe₃O₄ nanoparticles with two different mean sizes, and Ni_1 −xZn_xFe₂O₄ ferrites with 0 ≤ x ≤ 0.8 has been measured with three approaches: static hysteresis loops areas, dynamic hysteresis loops areas and hyperthermia of a water solution. For dynamic loops and thermometric measurements, specific experimental setups have been developed, that operate at comparable frequencies (≈ 69 kHz and ≈ 100 kHz respectively) and rf magnetic field peak values (up to 100 mT). The hyperthermia setup has been fully modelled to provide a direct measurement of the SAR of the magnetic nanoparticles by taking into account the heat exchange with the surrounding environment in non-adiabatic conditions and the parasitic heating of the water due to ionic currents.ResultsDynamic hysteresis loops are shown to provide an accurate determination of the SAR except for superparamagnetic samples, where the boundary with a blocked regime could be crossed in dynamic conditions. Static hysteresis loops consistently underestimate the specific absorption rate but can be used to select the most promising samples.ConclusionsA means of reliably measure SAR of magnetic nanoparticles by different approaches for hyperthermia applications is presented and its validity discussed by comparing different methods.General significanceThis work fits within the general subject of metrological traceability in medicine with a specific focus on magnetic hyperthermia. This article is part of a Special Issue entitled "Recent Advances in Bionanomaterials" Guest Editor: Dr. Marie-Louise Saboungi and Dr. Samuel D. Bader.     

磁性纳米颗粒固定化乙醇脱氢酶的研究

本研究采用3-丙氨基三乙氧基硅烷(APTES)和戊二醛修饰包裹有SiO2磁性Fe3O4纳米颗粒表面,将其作为固定化载体固定化乙醇脱氢酶,研究固定化条件对固定化效率的影响,并对固定化酶性质进行分析。研究发现,当Fe3O4@SiO2纳米颗粒修饰上氨基和醛基后依然具有良好的水分散性和胶体稳定性,适合作为固定化载体。通过单因素优化,发现当最适给酶量为11. 3U/100 mg,搅拌转速为150 r/min,固定化p H和固定化温度分别控制在6. 5和5℃～15℃,固定化时长为45 min时,具有较好的固定化效果,固定化率可达到60. 2%。在此条件下制备得到的固定化酶与游离酶相比,固定化酶具有良好的耐高温和耐碱性。所得固定化乙醇脱氢酶在连续使用8次后,固定化率仍保留在57%左右,表明该固定化酶具有较好的操作稳定性,可为连续生产NADH提供技术依据。     

Microwave absorption spectroscopy of DNA

By utilizing a novel approach to microwave spectrometry, we have measured the absolute absorption spectrum of plasmid DNA (pUC8.c2), in buffered aqueous solution, from 5 to 20 GHz. Our technique does not suffer from the same experimental difficulties that plague other methods. We observe no absorption resonances in this frequency range, but we do see broadband differences, between DNA and pure buffer, that are attributable to changes in the ionic conductivity of the solutions. These results constitute the first verification, by a totally different technique, of the absence of resonances in the microwave absorption spectrum of DNA, and the first data obtained by any technique in the 10–20-GHz band. © 1993 John Wiley & Sons, Inc.     

Microwave absorption in oligomers of ethylene glycol

The dielectric properties of biologically and pharmaceutically important low-molecular weight ethylene glycols H(-OCH2CH2-)n -OH (n = 1,2,4,6) were investigated to clarify the effect of chain length on the dielectric properties. The measurement of dielectric constant and dielectric loss was carried out over the frequency range 200 MHz to 20 GHz at temperatures of 25 degrees C to 55 degrees C. It is found that in these molecules microwave dielectric losses are significant. The dispersion behaviour of these molecules can be represented by Cole-Cole equation. The dielectric properties of these homologous ethylene glycols are discussed in terms of the effects of chain length and intermolecular hydrogen bonds regarding the molecular conformations. These wide frequency range dielectric data have also been discussed in view of the suitable selection of the oligomer of ethylene glycol for cosmetic preparations and other pharmaceutical applications with the intention of protection of the skin from weak microwave radiations present in the surrounding environment. These systematic microwave dielectric data with frequency and temperature variation are not available and are provided in this paper.     

Microwave dielectric absorption of DNA in aqueous solution

The dielectric properties of aqueous solutions of DNA were measured at frequencies ranging from 0.1 to 12 GHz. The results are analyzed using the Maxwell mixture theory and yield a value for the hydration of the DNA of about 0.4 g/g, which is in the range observed in other investigations. No evidence was found for an additional absorption effect at microwave frequencies, which has been predicted to occur in certain DNA analogs due to the vibrational excitation of the double helix by the applied microwave field.     

One-stop genomic DNA extraction by salicylic acid-coated magnetic nanoparticles

Salicylic acid-coated magnetic nanoparticles were prepared via a modified one-step synthesis and used for a one-stop extraction of genomic DNA from mammalian cells. The synthesized magnetic particles were used for magnetic separation of cells from the media by nonspecific binding of the particles as well as extraction of genomic DNA from the lysate. The quantity and quality were confirmed by agarose gel electrophoresis and polymerase chain reaction. The entire process of extraction and isolation can be completed within 30 min. Compared with traditional methods based on centrifugation and filtration, the established method is fast, simple, reliable, and environmentally friendly.     

Microstructure study of liposomes decorated by hydrophobic magnetic nanoparticles

Magnetoliposomes, consisting of liposomes and magnetic nanoparticles (MNPs), have been tailored as very promising delivery vehicles in biotechnology and biomedicine applications. In this paper, liposomes with hydrophobic MNPs were prepared. The hydrophobic MNPs were successfully embedded in the lipid bilayer, which was proved by the results obtained from transmission electron microscope, atomic force microscope, differential scanning calorimetry and steady state fluorescence measurements. Moreover, systematic researches were carried out to investigate the effects of hydrophobic MNPs concentration on the morphology and microstructure of liposomes. The results show that the lipid bilayer was saturated with the hydrophobic MNPs when the mass ratio of MNPs to lipid reached 0.002.     

Leukocyte transepithelial migration in lung induced by DMSA functionalized magnetic nanoparticles

Magnetic nanoparticles surface-covered with meso-2,3-dimercaptosuccinic acid (MNPs-DMSA) constitute a promising approach for tissue- and cell-targeted delivery of therapeutic drugs in the lung. However, they can also induce a transient transendothelial migration of leukocytes in the organ as a side effect after endovenous administration of MNPs-DMSA. We demonstrated that monocytes/macrophages constitute the main subpopulation of leukocytes involved in this process. Our recent research found that MNPs-DMSA upregulated the mRNA expression of E-, L- and P-selectin and macrophage-1 antigen and increased concentration of tumor necrosis factor α (TNFα) in lung, in a time dependent manner. The critical relevance of the β₂ integrin-dependent pathway in leukocyte transmigration elicited by MNPs-DMSA was demonstrated by use of knockout mice. Our work characterizes mechanisms of the pro-inflammatory effects of MNPs-DMSA in the lung and identifies β₂ integrin-targeted interventions as promising strategies to reduce pulmonary side effects of MNPs-DMSA during biomedical applications. In addition, MNPs-DMSA could be used as modulators of lung immune response.Key words: magnetic nanoparticles, DMSA, nanobiotechnology, transepithelial migration, cell adhesion molecules, integrins, monocytes, lungNanotechnology deals with structures of 100 nm or smaller in at least one dimension and has the potential to create many new materials and devices with a vast range of applications. Materials can be produced that are nanoscale in one dimension (for example, very thin surface coatings), in two dimensions (for example, nanowires and nanotubes) or in all three dimensions (for example, nanoparticles).Magnetic nanoparticles (MNPs) are a class of nanoparticles that can be manipulated using a magnetic field. MNPs are traditionally ferrite-based materials with the general formula MFe₂O₄, where M is a doubly charged metal-ion, such as iron, nickel or cobalt. Magnetic fluids (MFs) are colloidal mixtures composed of MNPs suspended in a carrier fluid, usually an organic or inorganic solvent. There is an increasing interest in developing biocompatible MFs for biomedical applications¹ for instance, for detection of circulating tumor cells,² contrast agents for magnetic resonance imaging³ and in an experimental cancer treatment called magnetic hyperthermia in which the fact that nanoparticles heat when they are placed in an alternative magnetic field is used.⁴ Another potential use includes attaching magnetic nanoparticles to drug/gene for targeting purposes.⁵ In order to be used for medical applications, magnetic nanoparticles are coated with a surfactant to prevent their agglomeration (due to van der Waals and magnetic forces) and allow the association of MNPs surface with different molecules.^6,7In previous studies, we have shown that MNPs surface-coated with meso-2,3-dimercaptosuccinic acid (MNPs-DMSA) (Fig. 1), with average diameter of about 9 nm, presented preferential distribution in the lung tissue, after intravenous administration in mice.^8–10 This target specificity of MNPs-DMSA offers a unique property that may be successfully exploited for the treatment of lung diseases.¹¹ In addition, we reported that the presence of MNPs-DMSA in the lung led to trafficking of leukocytes from blood vessels into pulmonary parenchyma and airspace and that interleukin-1 (IL-1) and interleukin-6 (IL-6) were overexpressed.¹² IL-1 acts as a trigger that activates a cascade of cytokine production and induces the production of a wide range of immunomodulatory cytokines.¹³ IL-6 is among the mediators regulated by IL-1 and is often increased in inflammatory processes in the lung.¹³ These differential expressions were particularly associated with blood vessels and cells of airway ducts suggesting that they could have some role during the recruitment process of inflammatory cells, as observed in histological analyses. In fact, these cytokines are commonly associated with the activation of cells concerning the expression of adhesion surface proteins.¹³ This is in agreement with several studies that described the requirement of IL-1α production in rat airways for full polymorphonuclear cell migration in models for immune-complex deposition or inhalation of cement dust, coal dust or diesel exhaust particles.^14–16Open in a separate windowFigure 1Schematic representation of DMSA-functionalized maghemite nanoparticles.Cell migration plays a key role in a wide variety of biological phenomena. This process is particularly important for leukocyte function and the inflammatory response. A mechanistic understanding of cellular interactions with synthetic surfaces, particularly in the context of inflammatory and healing responses, has been a major goal of biomaterial science.Leukocyte trafficking in the lung involves transendothelial migration, migration in tissue interstitium and transepithelial migration. In addition, leukocyte emigration involves regulatory mechanisms including complement activation, cytokine regulation, chemokine production, activation of adhesion molecules and their respective counter receptors. The process is presumably initiated and modulated by the production of early response cytokines such as IL-1 and tumor necrosis factor (TNF) from lung cells, especially from alveolar macrophages, setting the stage for leukocyte migration through endothelium.¹⁷ On the other hand, ensuing production of interleukin-10 (IL-10) brings into play powerful anti-inflammatory factors that strongly regulate inflammatory responses, functioning as intrinsic regulators of the lung inflammatory response.^18,19Tissue infiltration by circulating leukocytes is a three-step process involving rolling on the endothelium, attachment to the endothelium and transmigration across the endothelial cells lining blood vessel walls (Fig. 2). Leukocyte migration out of the blood is initiated by leukocyte rolling on the luminal side of the endothelium, as mediated by the low-affinity receptors selectins (E-, L- and P-selectin).^20–22 Binding of selectins on leukocytes stimulates “outside-in” signals in these cells, increasing the affinity of the integrin family of receptors (cell surface receptors consisting of an α- and a β-subunit, which are grouped in distinct subfamilies based on β-subunit utilization), which then bind to endothelial cell adhesion molecules such as intercellular adhesion molecule-1 [(ICAM-1)/CD54] and vascular cellular adhesion molecule-1 (VCAM-1). Function-blocking studies have identified the β₁ (CD29) and β₂ (CD18) integrins as the major players involved in leukocyte adhesion and migration.²³ Leukocyte integrin affinity is also rapidly increased by “inside-out” signals from leukocyte chemokine receptors triggered by chemokines displayed on the surface of endothelial cells.²⁴ With an increase in leukocyte integrin receptor affinity, leukocyte rolling is arrested.²⁴Open in a separate windowFigure 2Schematic representation of leukocyte endothelial migration into lung parenchyma.Using immunohistochemistry, we demonstrated that following injection of MF-DMSA, the distribution pattern of E-selectin and members of the β₂ integrin subfamily (macrophage-1 antigen, Mac-1; leukocyte function associated antigen-1, LFA-1) was changed in the lung vessels, but not of β₁ integrin.¹⁰ For L and P selectins no differences were observed between treated and control animals. However, for E-selectin, labeling was found in the endothelium of veins and venules 12 h after MF-DMSA administration, but not in the lung''s vascular compartments of the control and 4 h treatment groups.¹² Concerning integrins, in the control group, leukocytes labeled with Mac-1 and LFA-1 were found only in post-capillary sites. Four hours after MF-DMSA administration, leukocytes expressing these β₂ integrins were also found in capillaries.¹⁰ Our findings expand on other studies showing that the capillary network constitutes an important migration site in the lung.²⁵ Thus, the modulation of Mac-1 and LFA-1 expression in leukocytes located inside capillaries supports the importance of these integrins and capillaries for migratory activity in the lung, in this case after MF-DMSA administration. However, we cannot discard the participation of larger vessels in the migration induced by MNPs-DMSA. In fact, some images from our laboratory have showed that this is also a route used by the leukocytes after injection of these nanoparticles (Fig. 3).Open in a separate windowFigure 3Light microscopy image of leukocytes containing MNPs-DMSA inside a vein. Note that the cells (yellow arrows) are close or attached to the endothelium.It is worth noting that 12 h after MF-DMSA administration, leukocytes labeled with LFA-1 were observed only in post-capillary sites, similar to the control. We speculated that the absence of LFA-1 labeling in capillaries in the period of 12 h after MF-DMSA administration is due to the accentuated decrease of LFA-1 expression levels in the leukocyte over the course of time. In fact, as will be discussed below, we obtained a decrease in the LFA-1 mRNA 12 h after MNPs-DMSA administration. This point of view is in agreement with other studies that demonstrated the distinct contribution of LFA-1 and Mac-1 to transendothelial migration in the lung.²⁶ While both Mac-1 and LFA-1 participate in transendothelial migration at the beginning of the inflammatory process, over time Mac-1 becomes the predominant member of the β₂ integrin subfamily mediating migration of leukocytes.²⁶These results raised several questions related to MNPs-DMSA administration, such as: what is the time profile of leukocyte migration into the airspace? Which is the principal leukocyte subpopulation involved in this process? Is it a fact that the mechanism by which the presence of MNPs-DMSA induces transendothelial migration of leukocytes into the lung is based on their ability to somehow change the expression of cell adhesion molecules on leukocytes and lung vascular endothelial cells? Is β₂ or β₁ integrin, or both, the main receptor involved in MNPs-DMSA leukocyte-induced migration?Recently, we uncovered some of these answers including the main adhesion molecules that are involved in this migration. We first determined that the number of leukocytes in the bronchoalveolar lavage fluid reached its peak 12 h after MNPs-DMSA administration, decreasing to normal values in 48–72 h. Cytologic and FACS analysis demonstrated that the main subpopulation of leukocytes involved in this process was monocyte/macrophage.²⁷It is well known that the reticuloendothelial system, in particular macrophage cells, actively neutralizes and eliminates foreign matter from the body, including nonbiological particles. These and other particulated materials in the lung may lead to lung damage. In fact, transmission electron microscopy analysis clearly demonstrated an uptake of MNPs-DMSA by monocyte/macrophage cells,²⁷ indicating that this may be a mechanism of nanoparticle clearance used by the lung in order to avoid further damage. It is worth noting that an increase in the relative percentage of lymphocytes after MNPs-DMSA administration was also observed. The importance of this finding was not addressed in the paper, but we speculate that it could be important for the control of the inflammatory process initiated by the MNPs-DMSA injection. Failure in control of the inflammatory processes could potentially lead to chronic inflammatory diseases and pulmonary fibrosis. In spite of the fact that we did not determine which was the main source of the production of two different cytokines, one considered pro-inflammatory (TNFα) and the other anti-inflammatory (IL-10), we found an increase in the ratio of IL-10/TNFα cytokine release 12 h after MNPs-DMSA administration. This is clearly a signal that the inflammatory process was being controlled, in agreement with previous reports showing that IL-10 is able to limit the induction of cell adhesion molecules in the lung.²⁸ We presume that lymphocytes are taking part in this process. Further studies are necessary to clarify this point.The nature of the cells present in the pulmonary tissue parenchyma was not determined in this study. However, these cells were not able to cause tissue damage in the lung. We observed no histological or ultrastructural damage in the lung of animals treated with MNPs-DMSA, indicating that the nanoparticle-induced inflammation is not enough to cause chronic disease, such as pulmonary fibrosis.We then determined the effect of MNPs-DMSA on mRNA expression of selectins, integrin β₁ and integrin β₂.²⁷ We found that MNPs-DMSA upregulated the mRNA expression of E-, L- and P-selectin, as well as Mac-1. Further, using knockout mice (deficient in the β₂-subunit common to all β₂ integrins), we observed that, compared to wild-type mice, the recruitment of leukocytes to the airspace following administration of MNPs-DMSA was completely blocked in the former.²⁷ The fact that transmigration of β₂ integrin-deficient monocytes was affected when compared with wild-type monocytes strongly argues in favor of a major contribution by β₂ integrins to monocyte trans-epithelial migration in our system, which is additionally supported by the increase of mRNA of β₂ integrins, as cited above.We should remember, however, that the absence of change in LFA-1 and very late antigen-4 (VLA-4) mRNA does not exclude a role for them in leukocyte migration induced by MNPs-DMSA. Integrins are cell adhesion molecules constitutively expressed on the cell surface and also stored within intracellular vesicles.^29,30 In addition, transendothelial migration of leukocytes depends not only on the number of integrins on the cell surface but also on the change in conformation of these molecules reflecting their activation.³² Therefore, our results did not exclude the possibility that MNPs-DMSA induce the activation of LFA-1 and VLA-4 constitutively located on the surface of leukocytes or the translocation of these integrins from intracellular vesicles to the plasma membrane. On the other hand, the absence of a significant change in the mRNA expression of VCAM-1, which is the major endothelial cell ligand for VLA-4, can be regarded as an indirect indicator that VLA-4 is not involved in this process.The fact that an increase in the mRNA of Mac-1 occurred and there is no change in the mRNA levels of VLA-4 (and LFA-1) corroborates the hypothesis that migration of leukocytes induced by MNPs-DMSA is mainly dependent on β₂ integrins and not β₁ integrins pathway. In addition, we can presume that MAC-1 is the main β₂ integrin molecule involved in the process of leukocyte trafficking.The increased use of nanoparticles in medicine has raised concerns on their ability to gain access to privileged sites in the body. In fact, a study has shown that, in some cases, they can potentially cause damage to tissues located behind cellular barriers. Therefore, it is fundamental to understand the mechanisms underlying interactions between nanoparticles and the body, for their safe and effective use. In the case of MNPs-DMSA, we can use this knowledge for treatment of lung diseases when associated with drugs, as well as for downregulation or upregulation of the local immune system.One important question still unanswered about the use of magnetic nanoparticles in lung disease treatments is what could be expected if more than one dose is necessary in a short period of time. Recent research of Mejias et al.³¹ was close to answer this question. In their study the authors injected repeated doses (nine in total) of magnetic nanoparticles stabilized with DMSA, but unfortunately, they did not analyze the lungs, assuming that the particles would be stocked in the liver, spleen and kidney. For these organs, however, the authors did not refer to any observed damage. We believe that the answer to this question is related with several factors such as physical-chemical features of the nanoparticles (size, hydrodynamic radius, etc.) interval between the injections, amount of iron injected, among others. These features are also important for a second open question: what happens if the organ has a preexistent disease? Further studies are necessary to clarify this point. It is important to minimize, in all cases, the amount of injected iron, increasing, when possible, the amount of drug attached to the nanoparticles. The use of magnetic nanoparticles is already a reality as a contrast agent. It is possible that in the future they also can be used as drug delivery carriers.In resume our work characterizes mechanisms of the pro-inflammatory effects of MNPs-DMSA in the lung and identifies β₂ integrin-targeted interventions as promising strategies to reduce pulmonary side effects of MNPs-DMSA during biomedical applications. In addition, MNPs-DMSA could be used as modulators of lung immune response.     

New magnetic nanoparticles for biotechnology

Paramagnetic carriers, which are linked to antibodies enable highly specific biological cell separations. With the colloidal synthesis of superparamagnetic Co and FeCo nanocrystals with superior magnetic moments the question about their potential to replace magnetite as the magnetically responsive component of magnetic beads is addressed. Starting from a magnetic analysis of the corresponding magnetophoretic mobility of Co and FeCo based alloys their synthesis and resulting microstructural and magnetic properties as function of the underlying particle size distribution are discussed in detail. The stability of the oleic acid ligand of Co nanocrystals has been investigated. The oxidation kinetics were quantified using magnetic measurements. As a result, this ligand system provides sufficient protection against oxidation. Furthermore, the kinetics of the synthesis of Fe(50)Co(50) nanoparticles has been monitored employing Fourier transform infra red (FT-IR) spectroscopy and is modeled using a consecutive decomposition and growth model. This model predicts the experimentally realized FeCo nanoparticle composition as a function of the particle size fairly well. High-resolution transmission electron microscopy (HRTEM) was performed to uncover the resulting microstructure and composition on a nanometer scale.     

Extraction of DNA from soil using nanoparticles by magnetic bioseparation

Aims: To develop a simple, rapid and inexpensive soil DNA extraction protocol. Methods and Results: The protocol relies on the use of superparamagnetic silica‐magnetite nanoparticles for the isolation and purification of DNA from soil samples. DNA suitable for use in molecular biology applications was obtained from a number of soil samples. Conclusions: The DNA extracted using the tested method successfully permitted the PCR amplification of a fragment of the bacterial 16S rDNA gene. The extracted DNA could also be restriction endonuclease digested. Significance and Impact of the Study: The protocol reported here is simple and permits rapid isolation of PCR‐ready soil DNA. The method requires only small quantities of soil sample, is scalable and suitable for automation.     

Novel microwave-assisted digestion by trypsin-immobilized magnetic nanoparticles for proteomic analysis

In this study, a novel microwave-assisted protein digestion method was developed using trypsin-immobilized magnetic nanoparticles (TIMNs). The magnetic nanoparticles worked as not only substrate for enzyme immobilization, but also excellent microwave irradiation absorber and, thus, improved the efficiency of microwave-assisted digestion greatly. Three standard proteins, bovine serum albumin (BSA), myoglobin, and cytochrome c, were used to optimize the conditions of this novel digestion method. With the optimized conditions, peptide fragments produced in very short time (only 15 s) could be identified successfully by MALDI-TOF-MS. When it was compared to the conventional in-solution digestion (12 h), equivalent or better digestion efficiency was observed. Even when protein quantity was as low as micrograms, this novel digestion method still could digest proteins successfully, while the same samples by conventional in-solution digestion failed. Moreover, with an external magnetic field, the enzyme could be removed easily and reused. It was verified that, after 4 replicate runs, the TIMNs still kept high activity. To further confirm the efficiency of this rapid digestion method for proteome analysis, it was applied to the protein extract of rat liver. Without any preparation and prefractionation processing, the entire proteome digested by TIMNs in 15 s went through LC-ESI-MS/MS direct analysis. The whole shotgun proteomic experiment was finished in only 1 h with the identification of 313 proteins ( p < 0.01). This new application of TIMNs in microwave-assisted protein digestion really opens a route for large-scale proteomic analysis.     

Separation of murine neutrophils and macrophages by thermoresponsive magnetic nanoparticles

Magnetic particles have been used widely in both biotechnological and medical fields, including for immunoassay, enzyme immobilization, drug transport, and immunological diagnosis. Especially particles with bioactive molecules such as antibodies and streptavidin are very useful tools for cell separation. Here we report affinity selection of neutrophils and macrophages from peritoneal inflammatory cells performed by thermoresponsive magnetic nanoparticles conjugated with macrophage-specific anti-F4/80 antibody. The magnetic nanoparticles, which are capped with thermoresponsive polymers, are aggregated by heating the particles over 30 degrees C and show their intrinsic magnetism. The neutrophils are concentrated approximately 90% by these magnetic nanoparticles without any activation, indicating that this novel cell separation method could fulfill a wide range of applications in analysis of the isolation of fragile cells such as neutrophils.