Core-shell Superparamagnetic Nanoparticles Research Articles

Core-Shell-Nanoparticles with Superparamagnetic Properties for Novel Applications as Biomaterials

Abstract Due to the increasing average age of the population, the number of implants is also increasing and with it the number of explantations. Therefore, facilitated implant removal is of great interest. A nanocomposite consisting of superparamagnetic core-shell nanoparticles (CSNPs) and a synthetic polymer is supposed to be used as implant coating, aiming for a stimulus-inducible modification of the composite’s rheological properties by hyperthermia. Here, the first steps following this concept, the synthesis and modification of the CSNP are reported. In this work magnetite nanoparticles build the core and are surrounded by a periodic mesoporous organisilica (PMO) shell. For this reason, the CSNP are referred to as magnetic PMO (mPMO) particles in the following.

THE SYSTEM FOR COMPLEX MAGNETIC SUSCEPTIBILITY MEASUREMENT OF NANOPARTICLES WITH 3D PRINTED CARCASS FOR INTEGRATED RECEIVE COILS

The article concerns the research on the properties of core-shell superparamagnetic nanoparticles in the context of their use in medicine for diagnostics and therapy. The article presents a system for impedance (AC) spectroscopy of nanoparticles with a new arrangement of receive coils. A significant modification was the position of the reference coil in relation to the receive coils as well as the method of winding and routing the wires on the carcass. The 3D printing technique was used in the production of the measuring coil system. The aim of the work was to experimentally verify the developed measurement system and analyze its properties. The system tests were carried out at low frequencies ranging from 2 to 50 kHz. Complex magnetic susceptibility was measured for superparamagnetic iron oxide nanoparticles in polymer shells in a physiological saline solution. The obtained results confirmed the relevance of the concept of the measurements. In summary, the observed properties of the realized system are discussed and further directions of its development are proposed.

Ultrasound-assisted solid phase microextraction-HPLC method based on Fe3O4@SiO2-NH2-molecularly imprinted polymer magnetic nano-sorbent for rapid and efficient extraction of harmaline from Peganum harmala extract

In the present study, a magnetic molecularly imprinted polymer (MMIP) was synthesized for the extraction of harmaline from Peganum harmala by dispersive solid-phase microextraction (DSPME). The MMIP for selective and intelligent extraction of harmaline with excellent functionality and high selectivity was synthesized using the sol-gel method with functionalized superparamagnetic core-shell nanoparticles, ethylene glycol dimethacrylate (EDMA) as a cross-linker, methacrylic acid (MAA) as a functional monomer, and 2,2-azobisisobutyronitrile (AIBN) as a porogen. To study the properties and morphology of the coated polymer, FT-IR spectroscopy, FESEM, TEM images, and VSM were used. The DSPME-HPLC-UV equipment was used to quantify and analyze the data obtained from harmaline extraction. In this research, the efficiency of the synthesized polymer in harmaline extraction was modeled and optimized using the response surface methodology based on central composite design (RSM-CCD). In addition, for modeling the isotherm of harmaline sorption by the MMIP, Langmuir and Freundlich isotherm equations were used. The obtained results showed that the extraction of harmaline with the MMIP was well described with Freundlich isotherm. The results of the validation of the method showed that the measurement of harmaline in the concentration range of 1.0–4000 ng mL−1 followed a linear relationship (R2 = 9986.0). Moreover, the accuracy or repeatability index (% RSD) was determined to be < 10, and the LOQ and LOD values were 0.526 and 0.158 ng mL−1, respectively. The results of this study showed that the DSPME technique by using the synthesized MMIP as an effective sorbent with high efficiency and capacity could be utilized for pre-concentration and extraction of harmaline from real and complex samples.

Release and Detection of microRNA by Combining Magnetic Hyperthermia and Electrochemistry Modules on a Microfluidic Chip.

The heating of a biologic solution is a crucial part in an amplification process such as the catalytic detection of a biological target. However, in many situations, heating must be limited in microfluidic devices, as high temperatures can cause the denaturation of the chip components. Local heating through magnetic hyperthermia on magnetic nano-objects has opened the doors to numerous improvements, such as for oncology where a reduced heating allows the synergy of chemotherapy and thermotherapy. Here we report on the design and implementation of a lab on chip without global heating of samples. It takes advantage of the extreme efficiency of DNA-modified superparamagnetic core–shell nanoparticles to capture complementary sequences (microRNA-target), uses magnetic hyperthermia to locally release these targets, and detects them through electrochemical techniques using ultra-sensitive channel DNA-modified ultramicroelectrodes. The combination of magnetic hyperthermia and microfluidics coupled with on-chip electrochemistry opens the way to a drastic reduction in the time devoted to the steps of extraction, amplification and nucleic acids detection. The originality comes from the design and microfabrication of the microfluidic chip suitable to its insertion in the millimetric gap of toric inductance with a ferrite core.

Well Defined Poly(Methyl Methacrylate)-Fe3O4/Poly(Vinyl Pivalate) Core-Shell Superparamagnetic Nanoparticles: Design and Evaluation of In Vitro Cytotoxicity Activity Against Cancer Cells.

The objective of this work is to develop and characterize polymeric nanoparticles with core–shell morphology through miniemulsion polymerization combined with seeded emulsion polymerization, aiming at the application in the treatment of vascular tumors via intravascular embolization. The synthesis of the core–shell nanocomposites was divided into two main steps: (i) Formation of the core structure, consisting of poly(methyl methacrylate)/magnetic oxide coated with oleic acid (OM-OA) via miniemulsion and (ii) shell structure produced through seeded emulsion polymerization of vinyl pivalate. Nanocomposites containing about 8 wt.% of OM-OA showed high colloidal stability, mean diameter of 216.8 nm, spherical morphology, saturation magnetization (Ms) of 4.65 emu·g−1 (57.41 emu·g−1 of Fe3O4), preserved superparamagnetic behavior and glass transition temperature (Tg) of 111.8 °C. TEM micrographs confirmed the obtaining of uniformly dispersed magnetic nanoparticles in the PMMA and that the core–shell structure was obtained by seeded emulsion with Ms of 1.35 emu·g−1 (56.25 emu·g−1 of Fe3O4) and Tg of 114.7 °C. In vitro cytotoxicity assays against murine tumor of melanoma (B16F10) and human Keratinocytes (HaCaT) cell lines were carried out showing that the core–shell magnetic polymeric materials (a core, consisting of poly(methyl methacrylate)/Fe3O4 and, a shell, formed by poly(vinyl pivalate)) presented high cell viabilities for both murine melanoma tumor cell lines, B16F10, and human keratinocyte cells, HaCaT.

Biocompatible superparamagnetic core-shell nanoparticles for potential use in hyperthermia-enabled drug release and as an enhanced contrast agent

Superparamagnetic iron oxide nanoparticles (SPIONs) and core-shell type nanoparticles, consisting of SPIONs coated with mesoporous silica and/or lipid, were synthesised and tested for their potential theranostic applications in drug delivery, magnetic hyperthermia and as a contrast agent. Transmission Electron Microscopy (TEM) confirmed the size of bare and coated SPIONs was in the range of 5–20 nm and 100–200 nm respectively. The superparamagnetic nature of all the prepared nanomaterials as indicated by Vibrating Sample Magnetometry (VSM) and their heating properties under an AC field confirm their potential for hyperthermia applications. Scanning Column Magnetometry (SCM) data showed that extrusion of bare-SPION (b-SPION) dispersions through a 100 nm polycarbonate membrane significantly improved the dispersion stability of the sample. No sedimentation was apparent after 18 h compared to a pre-extrusion estimate of 43% settled at the bottom of the tube over the same time. Lipid coating also enhanced dispersion stability. Transversal relaxation time (T2) measurements for the nanoparticles, using a bench-top relaxometer, displayed a significantly lower value of 46 ms, with a narrow relaxation time distribution, for lipid silica coated SPIONs (Lip-SiSPIONs) as compared to that of 1316 ms for the b-SPIONs. Entrapment efficiency of the anticancer drug, Doxorubicin (DOX) for Lip-SPIONs was observed to be 35% which increased to 58% for Lip-SiSPIONs. Moreover, initial in-vitro cytotoxicity studies against human breast adenocarcinoma, MCF-7 cells showed that % cell viability increased from 57% for bSPIONs to 82% for Lip-SPIONs and to 87% for Lip-SiSPIONs. This suggests that silica and lipid coatings improve the biocompatibility of bSPIONs significantly and enhance the suitability of these particles as drug carriers. Hence, the magnetic nanomaterials prepared in this work have potential theranostic properties as a drug carrier for hyperthermia cancer therapy and also offer enhancement of contrast agent efficacy and a route to a significant increase in dispersion stability.

Advanced core-shell EDTA-functionalized magnetite nanoparticles for rapid and efficient magnetic solid phase extraction of heavy metals from water samples prior to the multi-element determination by ICP-OES.

A method for preconcentration and simultaneous determination of trace heavy metals in water media by core-shell superparamagnetic nanoparticles with the immobilized derivative of ethylenediaminetriacetic acid (referred to as MNPs/SiO2-EDTA) is proposed. The specific layer-by-layer covering of magnetite endowed the new material with essentially increased chemical stability of MNPs including acidic media and improved the affinity toward traces of toxic metal ions. The initial and modified materials were characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy, transmission and scanning electron microscopies, elemental analysis, and vibrating sample magnetometry. The obtained particles were nanodimensional with a7-12-nm magnetic core and a4-6-nm silica shell. The MNPs/SiO2-EDTA quantitatively removes heavy metals from contaminated media at pH ≥ 3.5 within 15min. The adsorption data were successfully fitted to the pseudo-second-order kinetic model. The preconcentration factor was 150 and maximum adsorption capacity was 36.9mgg-1 for Cu(II), 108.8mgg-1 for Pb(II), 30.9mgg-1 for Zn(II), 34.32mgg-1 for Cr(III), and 59.5mgg-1 for Cd(II). Due to high stability in the wide range of pH, the magnetic adsorbent can be regenerated at least six times using0.1M HNO3. Following adsorption/desorption, determinationof metal ions isprovided by inductively coupled plasma optical emission spectrometry (ICP-OES) . The linear range of theproposed method is 0.1 - 200μgL-1. The limits of detection (LOD) are 0.12μgL-1 for Zn(II); 0.06μgL-1 for Cd(II); 0.39 for Cu(II); 0.15μgL-1 for Cr(III); and 0.76μgL-1 for Pb(II). The method performance was evaluated in the analysis of environmental, tap, and wastewater samples with recoveries in the range of 94.0-104.0%.

Functionalized Magnetic Nanoparticles as Catalysts for Enantioselective Henry Reaction.

With the aim to easily recover and reuse the catalyst, an efficient amino alcohol catalyst previously tested in the asymmetric addition of diethylzinc to several aromatic aldehydes has been immobilized on proper functionalized superparamagnetic core–shell magnetite–silica nanoparticles and employed in the Henry reaction in the semi-homogeneous phase. The nanocatalyst exhibits a promising catalytic activity that remains unchanged in the three catalytic cycles performed. The results prove that highly efficient catalysts, by being immobilized on suitable magnetic nanosupports, can be easily recovered and reused, maintaining their catalytic behavior.

Preparation of core-shell magnetic molecularly imprinted polymer nanoparticle for the rapid and selective enrichment of trace diuron from complicated matrices

A novel magnetic MIPs (DUMIPs) was prepared by surface molecular imprinting method using superparamagnetic core-shell nanoparticle (Fe3O4@SiO2) as the sacrificial support matrix, herbicide diuron as template, α-methacrylic acid as the functional monomer, trimethylolpropane trimethacrylate as the crosslinker, azobisisobutyronitrile as the initiator, and acetonitrile as the porogen. Highly cross-linked porous surface and excellent magnetic property were characterized by Fourier-transform infrared spectroscopy, transmission electron microscopy, and vibrating sample magnetometer, respectively. The adsorption capacity of DUMIPs was 8.1 mg g−1, 2.6-fold over its corresponding non-imprinted polymers (DUNIPs). The adsorption in DUMIPs was considered as multilayer adsorption and posed high affinity to diuron, due to the better fitting to Freundilich isotherm. Competitive recognition study demonstrated DUMIPs had highly selective binding diuron. DUMIPs, as an influential sorbent has been used for selective extraction of diuron from environmental samples (paddy field water, paddy soil and grain seedlings) and the elution was determined by high efficiency liquid chromatography (HPLC). In this analytical method, various factors affecting the extraction efficiency such as pH, sorbent dosage, utilization efficiency and volumes of eluent were simultaneously investigated. Under the optimal conditions, the linearity of the method obtained is in the range of 0.02–10.0 mg L−1. The limit of detection is 0.012 mg L−1. In four spiked levels (0.04, 0.2, 1.0, and 4.0 mg kg−1), the recoveries of diuron in real samples are in the range of 83.56%–116.10% with relative standard deviations in the range of 1.21–6.81%. Importantly, compared to C18-SPE column, the MMIPs exhibited convenient separation by external magnetic field, strong clean-up capacity, and selective enrichment for diuron. Thus, the DUMIPs-based method is great potential for efficient sample preparation in the determination of trace amounts of diuron residues in complex matrices.

Bis-salophen palladium complex immobilized on Fe3O4@SiO2 nanoparticles as a highly active and durable phosphine-free catalyst for Heck and copper-free Sonogashira coupling reactions.

New Fe3O4@SiO2 core-shell superparamagnetic nanoparticles functionalized by a bis-salophen Schiff base Pd complex were synthesized and employed as an efficient magnetic nanocatalyst in the Heck and Sonogashira cross coupling reactions. The synthesized nanostructures were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), dynamic light scattering (DLS), energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), elemental analysis (CHN), cyclic voltammetry (CV), Brunauer-Emmett-Teller analysis (BET), and UV-vis spectroscopy. The morphology and size of the nanoparticles were investigated by FE-SEM and TEM analyses. Furthermore, the magnetic properties of the catalyst were investigated by VSM analysis. The loading content and leaching amounts of palladium on the catalyst were measured by inductively coupled plasma (ICP) analysis. Also, the thermal behavior of this magnetic heterogeneous catalyst was studied using a TGA instrument. This heterogeneous catalytic system showed a good performance in the coupling of aryl halides with alkynes (Sonogashira reaction) as well as aryl halides with alkene derivatives (Heck reaction). High to excellent yields were achieved for these C-C coupling reactions. The catalyst can be simply separated from the reaction media by an external magnet and reused for eight consecutive runs without any significant loss of activity. Finally, the kinetics of the reactions were studied in this work.

Synthesis and characterization of novel Cu(II) complex coated Fe3O4@SiO2 nanoparticles for catalytic performance

In this study, a convenient method for the synthesis of arylaminotetrazoles has been developed using a copper (II)-aminotetrazole complex immobilized on silica-coated Fe3O4 (Fe3O4@SiO2) nanoparticles (Fe3O4@SiO2-aminotet-Cu(II)) as a novel and efficient magnetically catalyst. The constructed superparamagnetic core-shell nanoparticles were successfully prepared, as proven using different spectroscopic techniques such as fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscope (TEM), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), thermogravimetry and differential thermogravimetry (TG-DTG) and vibrating sample magnetometer (VSM) analysis. The applicability of Fe3O4@SiO2-aminotet-Cu(II) magnetic catalyst allows the efficient synthesis of a variety of arylaminotetrazoles from the reaction between various arylcyanamides with sodium azide in high yields. The effect of catalyst loading was investigated. In addition, the reaction mechanism for the synthesis of arylaminotetrazoles was reasonably proposed. Results show that the 1-aryl-5-amino-1H-tetrazole (B isomer) and 5-arylamino-1H-tetrazole (A isomer) can be obtained from the arylcyanamides carrying electron-donating and electron-withdrawing substituents, respectively. This procedure offers a simple methodology, relatively short reaction times, easy work-up, high yields of the products and a cleaner reaction with elimination of hydrazoic acid (HN3). Moreover, catalyst can be conveniently recovered through the use of external magnet and reused for at least 6 times without any significant loss of its activity.

Sequential synthesis of a magnetic nano-adsorbent: How the first step identifies the final product

Three types of super paramagnetic core-shell nanoparticles have creatively been synthesized via three basic substances, Fe2+/Fe3+, methacrylic acid (MAA), and 2,2′-azobisisobutyronitrile (AIBN). It has been demonstrated that the order of addition of starting materials determines the type of products. Methacrylic acid coated magnetic nanoparticles (Fe3O4@MAA) with abundant double bonds on the surface, poly methacrylic acid coated magnetic nano particles (Fe3O4@PMAA) having plenty of surface carboxylic groups, and amphiphilic shell of methacrylic acid polymer on magnetic nano particles core (Fe3O4@AMPH) having both carboxyl and alkyl groups on the surface were prepared in three, separate one-pot, sequential synthesis. At first, the resultant magnetic nanoparticles (MNPs) were characterized by transmission electron microscopy (TEM), dynamic light scattering, X-ray spectroscopy, Fourier transform infrared spectroscopy (FTIR) and thermal analysis. Then, the colloidal stability of the synthesized particles was investigated in several common solvents such as water, 1-propanol, chloroform, and edible oil. Finally, the application of each nanoparticle was discussed. It was found that Fe3O4@MAA can be successfully applied as a core in polymerization procedure. Fe3O4@PMAA performed well in nickel uptake and can therefore be used as magnetic solid sorbent in nickel pre-concentration and remediation. Fe3O4@AMPH was well dispersed in oil, suggesting that it can be successfully used as a good extractor in dispersive solid phase pre-concentration and cleanup of both hydrophilic and hydrophobic compounds in heated edible oil samples.

Influence of Grafted Block Copolymer Structure on Thermoresponsiveness of Superparamagnetic Core–Shell Nanoparticles

The morphology and topology of thermoresponsive polymers have a strong impact on their responsive properties. Grafting onto spherical particles has been shown to reduce responsiveness and transition temperatures; grafting of block copolymers has shown that switchable or retained wettability of a surface or particle during desolvation of one block can take place. Here, doubly thermoresponsive block copolymers were grafted onto spherical, monodisperse, and superparamagnetic iron oxide nanoparticles to investigate the effect of thermal desolvation on spherical brushes of block copolymers. By inverting the block order, the influence of core proximity on the responsive properties of the individual blocks could be studied as well as their relative influence on the nanoparticle colloidal stability. The inner block was shown to experience a stronger reduction in transition temperature and transition enthalpy compared to the outer block. Still, the outer block also experiences a significant reduction in responsiveness due to the restricted environment in the nanoparticle shell compared to that of the free polymer state. The demonstrated pronounced distance dependence importantly implies the possibility, but also the necessity, to radially tailor polymer hydration transitions for applications such as drug delivery, hyperthermia, and biotechnological separation for which thermally responsive nanoparticles are being developed.

Magnetic properties, exchange bias, and memory effects in core-shell superparamagnetic nanoparticles of La0.67Sr0.33MnO3

The static magnetic properties and memory and exchange bias effects have been studied in sol-gel prepared La0.67Sr0.33MnO3 (LSMO) nanoparticles. Transmission electron microscopy (TEM) micrographs and static magnetization show log-normal particle and magnetic size distributions with a core-shell structure. Analysis of the magnetization measurements indicates the presence of a magnetic structure with a 7.8 nm core radius and a magnetic dead layer of thickness 1.6 nm in the LSMO nanoparticles, which comprises about 40% of the volume. The disordered spins in the shell freeze at lower temperatures than the core and produce a surface spin glass state exhibiting a weak exchange bias effect. Field cooled and zero-field cooled magnetization measurements have been carried out to study the slow dynamics of the sample and associated magnetic memory effects; the results reveal the superparamagnetic behavior of LSMO nanoparticles described in terms of the magnetic size distribution rather than a superspin glass state.

Internalisation of core-shell superparamagnetic nanoparticles into human granulocytes

In this paper, multitasking core-shell Fe3O4@Cu@Au superparamagnetic nanoparticles (MNPs) functionalised either with folic acid (FA) or methotrexate (MTX) have been used for engulfment of human granulocytes. MNPs internalisation into phagocytes allows to use the cells as carriers thus avoiding the rapid clearance and decreasing of concentration commonly experienced in case of in vivo nanoparticles administration. MNPs have been coated with poly-L-lysine (PLL), which contributes to improve their dispersion into polar solvents. Moreover, this coating improves the cellular uptake and allows the further functionalisation with MTX and FA. Experimental evidences of granulocytes engulfment have been obtained by both SEM and fluorescence microscopy, upon prior labelling of the lysines residues with suitable fluorescent probes. The superparamagnetic nature of the MNPs makes the system easily drivable into a specific tissue upon exposure to a defined magnetic field. The success of the internalisation experiments indicates that the system is a promising tool as theranostic agent for treatment of a variety of diseases, including tumours.

Design of Super-Paramagnetic Core-Shell Nanoparticles for Enhanced Performance of Inverted Polymer Solar Cells.

Controlling the nature and transfer of excited states in organic photovoltaic (OPV) devices is of critical concern due to the fact that exciton transport and separation can dictate the final performance of the system. One effective method to accomplish improved charge separation in organic electronic materials is to control the spin state of the photogenerated charge-carrying species. To this end, nanoparticles with unique iron oxide (Fe3O4) cores and zinc oxide (ZnO) shells were synthesized in a controlled manner. Then, the structural and magnetic properties of these core-shell nanoparticles (Fe3O4@ZnO) were tuned to ensure superior performance when they were incorporated into the active layers of OPV devices. Specifically, small loadings of the core-shell nanoparticles were blended with the previously well-characterized OPV active layer of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). Upon addition of the core-shell nanoparticles, the performance of the OPV devices was increased up to 25% relative to P3HT-PCBM active layer devices that contained no nanoparticles; this increase was a direct result of an increase in the short-circuit current densities of the devices. Furthermore, it was demonstrated that the increase in photocurrent was not due to enhanced absorption of the active layer due to the presence of the Fe3O4@ZnO core-shell nanoparticles. In fact, this increase in device performance occurred because of the presence of the superparamagnetic Fe3O4 in the core of the nanoparticles as incorporation of ZnO only nanoparticles did not alter the device performance. Importantly, however, the ZnO shell of the nanoparticles mitigated the negative optical effect of Fe3O4, which have been observed previously. This allowed the core-shell nanoparticles to outperform bare Fe3O4 nanoparticles when the single-layer nanoparticles were incorporated into the active layer of OPV devices. As such, the new materials described here present a tangible pathway toward the development of enhanced design schemes for inorganic nanoparticles such that magnetic and energy control pathways can be tailored for flexible electronic applications.

Core–shell superparamagnetic nanoparticles with interesting properties as contrast agents for MRI

Core–shell nanoparticles (NPs) formed by superparamagnetic iron oxide NPs (SPIONs) coated with inorganic or organically modified (ORMOSIL) sol gel silica exhibited promising properties as negative contrast agents (CA) for MRI applications.The potentiality of these new core–shell NPs as negative CA for MRI is demonstrated and quantified.The longitudinal and transverse relaxivities of NPs with three different coating compositions were studied at a 7 T magnetic field: silica (TEOS), (3-aminopropyl) triethoxysilane (APTES) and (3-glycidoxypropyl) methyldiethoxysilane (GPTMS).Clearly, it was found that the core–shell NPs efficiency as CA was strongly depend on the SPIONs coating.All the three core–shell NPs studied presented a very small effect on the longitudinal relaxation time but a pronounced one on the transverse relaxation time, leading to a very high transverse longitudinal relaxivities ratio, decisive for their efficiency as negative CA for MRI.The effect of the core–shell NPs on the MRI contrast enhancement is obtained and quantified in a set of MRI of agar phantoms obtained at 7 T magnetic field and with a imaging gradient field of 1.6 T/m. The core–shell NPs were tested in Zebra-fish (Danio rerio) animal model. Zebra-fish MRI were obtained with animals injected with the three core–shell NPs and the contrast enhancement validated.

Magnetic-Assembly Mechanism of Superparamagneto-Plasmonic Nanoparticles on a Charged Surface

One-dimensional magnetoplasmonic nanochains (MPNCs) were self-assembled using Au-coated Fe3O4 core-shell superparamagnetic nanoparticles (Fe3O4@Au NPs) by applying an external static magnetic field. The assembly mechanism of the Fe3O4@Au NPs was investigated thoroughly, revealing that substrate-particle interactions, van der Waals forces, and magnetic forces play important roles in the formation and control of the MPNCs. Magnetic force microscopy (MFM) and vibrating sample magnetometry (VSM) were used to study the magnetic properties of the MPNCs, which were compared with those of Fe3O4 nanochains.

The fabrication and characterization of stable core-shell superparamagnetic nanocomposites for potential application in drug delivery

Two systems of core-shell superparamagnetic nanoparticles in the size range of 45–80 nm have been fabricated by the coating of bare magnetite particles with either mesoporous silica or liposomes and the loading/release of the anti-cancer drug Mitomycin C (MMC) from their surfaces has been investigated. The magnetic cores of size ∼10 nm were produced by a co-precipitation method in aqueous solution, with the silica coating containing an unstructured network of pores of size around 6 nm carried out using a surfactant-templating approach and the liposome coating achieved by an evaporation-immersion technique of the particles in a lipid solution. Stability measurements using a scanning column magnetometry technique indicated that the lipid-coating of the particles halts the sedimentation otherwise apparent in &amp;lt;1 h for the bare magnetite to produce an ultra-stable system and thereby overcome one of the main barriers to potential in-vivo applications. Whilst an increase in stability was also observed in the silica-coated system, it was still unstable over a few hours and will require further investigation. Magnetization curves of the coated systems were indicative of superparamagnetic behavior whilst the in vitro loading and release of MMC resulted in two distinctly different outcomes for the two systems: (i) the silica-coated particles saturated in &amp;lt;4 h to a loading of around 7 μg/mg of material, releasing about 6% at a near constant rate over 48 h whilst (ii) the lipid-coated particles saturated to around only 4 μg/mg over the same time period but with a subsequent rapid release rate over the first 3 h to 27% then rising near-linearly to a value of about 45% at the 48 h mark. This gives scope for systems' to be tuned to the appropriate rate and load delivery as required by clinical need with further investigations underway.

Development and characterization of magnetic molecularly imprinted polymers for the selective enrichment of endocrine disrupting chemicals in water and milk samples.

Analyses of four endocrine disrupting chemicals (EDCs) in water and milk samples were undertaken by using magnetic molecularly imprinted polymers (MMIPs). These were prepared via the surface molecular imprinting technique using super paramagnetic core-shell nanoparticle as support. Diethylstilbestrol (DES), which is a typical EDC, was employed as the template molecule. The obtained MMIPs were characterized using transmission electron microscope, Fourier transform infrared, X-ray diffraction, and vibrating sample magnetometer. Accordingly, the adsorption capacity and selectivity of prepared MMIPs were investigated. The binding isotherms were obtained for DES and fitted by the Freundlich isotherm model. A corresponding analytical method to determine four EDCs was developed. The recoveries of the spiked samples in pond water and pure milk range from 67.8 to 93.2% and from 65.3 to 92.5%, respectively. Coupled with high-performance liquid chromatography analysis, the prepared MMIPs were successfully applied to the analysis of EDCs in water and milk samples.