Instant magnetic labeling of tumor cells by ultrasound in vitro

Magnetic labeling of living cells creates opportunities for numerous biomedical applications. Here we describe an instantly cell magnetic labeling method based on ultrasound. We present a detailed study on the ultrasound performance of a simple and efficient labeling protocol for H-22 cells in vitro. High frequency focus ultrasound was investigated as an alternative method to achieve instant cell labeling with the magnetic particles without the need for adjunct agents or initiating cell cultures. Mean diameter of 168 nm dextran-T40 coated superparamagnetic iron oxide (SPIO) nanoparticles were prepared by means of classical coprecipitation in solution in our laboratory. H-22 tumor cells suspended in phosphate-buffered saline (PBS, pH=7.2) were exposed to ultrasound at 1.37 MHz for up to 120 s in the presence of SPIOs. The cellular uptake of iron oxide nanoparticles was detected by prussion blue staining. The viability of cells was determined by a trypan blue exclusion test. At 2 W power and 60 s ultrasound exposure in presence of 410 μg/ml SPIOs, H-22 cell labeling efficiency reached 69.4±6.3% and the labeled cells exhibited an iron content of 10.38±2.43 pg per cell. Furthermore, 95.2±3.2% cells remained viable. The results indicated that the ultrasound protocol could be potentially applied to label cells with large-sized magnetic particles. We also calculated the shear stress at the 2 W power and 1.37 MHz used in experiments. The results showed that the shear stress threshold for ultrasonically induced H-22 cell reparable sonoporation was 697 Pa. These findings provide a quantitative guidance in designing ultrasound protocols for cell labeling.     

Preparation and physical properties of polypropylene nanocomposites with dodecylated graphene nanoplatelets

The most important practical application of graphene nanoplatelets (GNPs) would be as nanofillers for polymer nanocomposites. However, the modification of GNPs is needed to improve the interfacial adhesion between GNPs and a polymer matrix. Therefore, in this study, the alkylation of GNPs by dodecylamine was carried out via chemical reactions between the amine groups of the alkyl amine and the carboxyl and epoxy groups of the oxidized GNPs’ surfaces. The dodecylation of the GNPs was confirmed by FTIR and TGA. The TGA data showed that the dodecyl-GNPs comprised alkyl groups 2.4%. Polypropylene nanocomposites with the dodecyl-GNPs were prepared in a platy shape by melt-blending followed by compression molding. The mechanical and thermal properties of the nanocomposites were measured by UTM, izod impact tester, DSC and DMA. Compared to the neat PP sample, the flexural modulus, flexural strength and impact strength of the PP nanocomposite with the dodecyl-GNPs 0.5 phr were increased by 38, 4 and 34% respectively. The fracture surfaces’ images of the nanocomposites taken by SEM showed that the dodecylation of the GNPs improved the interfacial adhesion between the GNPs and the PP matrix.     

Inclusion of magnetic dipole-dipole and hydrodynamic interactions in implant-assisted magnetic drug targeting

Mathematical modelling of the implant-assisted magnetic drug targeting system of Avilés, Ebner and Ritter is performed. In order to model the agglomeration of particles known to occur in this system, the magnetic dipole-dipole and hydrodynamic interactions are included. Such interactions were calculated previously by Mikkelsen et al. under low magnetic fields (~0.05 T) in microfluidic systems. Here, a higher magnetic field (0.7 T) is considered and the effect of interactions on two nanoparticles with a seed implant is calculated. The calculations were performed with the open-source software OpenFOAM. Different initial positions are considered and the system performance is assessed in terms of capture cross section. Inclusion of both interactions was seen to alter the capture cross section of the system by up to 7% in absolute terms.     

纳米材料与生物分子的相互作用与微结构特性

纳米材料是物理、化学、生物等领域所广泛关注的研究方向,主要分为无机材料、有机材料及复合材料。其中由纳米粒子与生物分子组成的复合材料因具有独特的光学、化学、电磁学等性质,在医学和医疗等方面有着良好的应用前景。此外,利用生物分子自组装的方法,可设计出具有复杂有序结构的复合材料。因此,研究纳米粒子和生物分子的相互作用对纳米材料的设计和应用有着重要的意义。本文从实验和计算机模拟两个方面综述了纳米粒子对生物分子(包括蛋白质、DNA、生物膜)结构特性以及热力学、动力学性质的影响,并概述了影响两者相互作用的多种因素,包括纳米粒子的尺寸、形状、浓度、表面特性等。     

Giant permittivity of three phase polymer nanocomposites obtained by modifying hybrid nanofillers with polyvinylpyrrolidone

In this work, the combination of graphene decorated with graphene quantum dots (G-D-GQDs) and barium titanate (BaTiO₃) nanoparticles filled poly (vinyledene fluoride) (PVDF) nanocomposites are prepared using solvent casting method. The modification of G-D-GQDs and BaTiO₃ nanoparticles with polyvinyl pyrrolidone (PVP) show finer dispersion in PVDF matrix as compared to unmodified G-D-GQDs and BaTiO₃ nanoparticles in PVDF matrix. XRD of PVDF nanocomposites shows the formation of α and β form of PVDF crystals. The incorporation of the combination of PVP modified BaTiO₃ nanoparticles and G-D-GQDs in PVDF matrix show a decrease in crystallization temperature (T_c), percent crystallinity (X_c) and increase in thermal stability as compared to unmodified PVDF/BaTiO₃/G-D-GQDs nanocomposites, due to interaction of PVP modified nanoparticles with PVDF. Further, the incorporation of the combination of 20 wt.% BaTiO₃ nanoparticles and 3 wt.% G-D-GQDs in PVDF matrix show a giant dielectric constant. The giant dielectric constant is achieved due to accumulation of more charges across conductor-insulator interface, more numbers of microcapacitor formed and enhanced interfacial compatibility between BaTiO₃/G-D-GQDs with PVDF through PVP. The loss tangent (tan δ) of PVP modified G-D-GQDs and BaTiO₃ nanoparticles and its PVDF nanocomposites is low due to lower leakage current, which make the material suitable for various applications.     

Correlating the breakdown strength with electric field analysis for polyethylene/silica nanocomposites

The experimental findings on the DC and AC breakdown strength of polyethylene/silica nanocomposites are reported and correlated with simulation results on the electric field distribution of possible nanocomposite models. Specifically, the effects of interphase permittivity and interparticle distances on the electric field intensity and the breakdown strength are discussed with the aid of the Finite Element Method Magnetics (FEMM) 4.2 software. The results showed that the presence of the interphase, when assigned a unique interphase permittivity value, led to variations in electric field distributions. The electric field also changed as adjacent nanoparticles separated from each other with different interparticle distances.     

The influence of temperature on magnetic and microwave absorption properties of Fe/graphite oxide nanocomposites

Fe/graphite oxide nanocomposites were prepared by inserting Fe³⁺ into layers of graphite oxide and then reducing Fe³⁺/graphite oxide compound at different reduced reaction temperatures in H₂. The composition, crystal structure, magnetic and microwave absorption properties of Fe/graphite oxide nanocomposites were investigated using elemental analysis, transmission electron microscope (TEM), X-ray diffraction (XRD), magnetic hysteresis curve and electromagnetic parameter analysis. The results show that the densities of samples are 2.43–2.47 g/cm³ and the nanocomposites are soft magnetic materials. The optimum reduced reaction temperature for preparing Fe/graphite oxide nanocomposites is 600 °C. With the increase of the thickness of the sample, the matching frequency tends to shift to the lower frequency region, and theoretical reflection loss becomes less at the matching frequency. Microwave absorption property of Fe/graphite oxide nanocomposites prepared at 600  °C (FeGO600) is the best. When the thickness is 1 mm, the maximum theoretical reflection loss of FeGO600 is −9 dB and the frequency region in which the maximum reflection loss is more than −6.0 dB is 11–18 GHz. In conclusion, FeGO600 is a good candidate for microwave absorbent due to its low density, wide frequency region for microwave absorption and large reflection loss.     

Gradient of molecular dynamics at the glass transition of PETg-Montmorillonite nanocomposites

Temperature Modulated Differential Scanning Calorimetry (TMDSC) is used to estimate Cooperative Rearranging Region (CRR) average sizes for polymer/clay nanocomposites, obtained by mixing polyethylene 1,4-cyclohexylenedimethylene terephthalate glycol (PETg) filled and organically modified nanoclay (C15A) following a master-batch process. Two different basal distances are obtained. It is shown that the greater the basal distance and the nanofiller content, the lower the heat capacity step at the glass transition temperature ΔCp(T_g), and the lower the CRR volume. It is also shown that the evolution of the CRR volume is consistent with the evolution of the fragility index obtained by DSC and Broadband Dielectric Spectroscopy (BDS) when the nanofiller content changes. The fragility index and the CRR size decreases can be correlated to nanofiller presence, hindering the molecular movements. From the Vollenberg and Heikens [34] approach, this behaviour can also be interpreted through the existence of an interfacial bilayer. This interfacial bilayer is composed by a zone, which is next to the nanofiller, with a density higher than the matrix one, followed by a more expanded zone with a density lower than the matrix one.     

Facile synthesis of multifunctional Ag/Fe3O4-CS nanocomposites for antibacterial and hyperthermic applications

Nanocomposites containing two or more functional constituents are attractive candidates for advanced nanomaterials. In this study, multifunctional Ag/Fe₃O₄-CS nanocomposites were successfully prepared, using chitosan as a stabilizing and cross-linking agent. The as-synthesized nanocomposites were characterized by Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDS), UV–visible spectrophotometer (UV–Vis) and vibrating sample magnetometer (VSM). The results demonstrated that Ag/Fe₃O₄-CS composite nanoparticles (NPs) were composed of parent components, Fe₃O₄ and Ag NPs, which were uniformly dispersed in the chitosan matrix. The hybrid NPs exhibited strong antibacterial property against Pseudomonas aeruginosa. With high magnetization value (67 emu/g), the synthesized Ag/Fe₃O₄-CS composite can be easily separated or recycled in potential biomedical applications. Furthermore, the results showed that the multicomponent hybrid nanostructures appeared to be the promising material for local hyperthermia, which can be used as thermoseeds for localized hyperthermia treatment of cancers.     

Ultrasound-assisted surface treatment of ZrO2 with BSA and incorporating in PVC to improve the properties of the obtained nanocomposites: Fabrication and characterization

This paper describes the preparation of poly(vinyl chloride) (PVC) nanocomposites (NCs) reinforced with modified zirconia (ZrO₂) nanoparticles (NPs). The ZrO₂ NPs were defined as efficient filler for PVC NCs. For achieving the best dispersion and improvement of properties, the surface of ZrO₂ NPs was modified by Bovine Serum Albumin (BSA). Carboxylic acids and amines are important functional groups of BSA which handle the grafting BSA on the surface of ZrO₂ NPs. The PVC/ZrO₂-BSA NCs were fabricated by incorporation of various amounts of the ZrO₂-BSA NPs (3, 6 and 9 wt%) into PVC matrix. All the above processes were accomplished by ultrasonication as a green and environmentally-friendly method. Also, the magnetic and mechanical stirrer was used for the preparation of samples but the results are not suitable and the aggregation was observed which indicated the use of ultrasonic irradiation is the best method for the preparation of NC. The products were characterized by Fourier transform infrared spectroscopy, Transmission electron microscopy, Field emission scanning electron microscopy, X-ray diffraction, Thermogravimetric analysis, Ultraviolet–visible spectroscopy, photoluminescence spectroscopy, energy dispersive X-ray spectroscopy, wettability, and mechanical tests. The achieved PVC/ZrO₂-BSA NCs showed high thermal stability, good mechanical, optical and wettability properties compared to the pure PVC. In addition, among the obtained NCs, the PVC/ZrO₂-BSA NC 6 wt% showed the best improvement.     

Ex situ synthesis and optical properties of ZnO-PbS nanocomposites

Zinc oxide (ZnO) and lead sulphide (PbS) nanoparticles separately synthesized by a precipitation method were combined by an ex situ route to prepare ZnO-PbS nanocomposites with different molar ratios of ZnO and PbS. The structure and morphology of the ZnO, PbS and ZnO-PbS samples were analyzed with X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). A UV-vis spectrophotometer was used to collect the absorption and 325 nm He-Cd and 488 nm Ar lasers were used to collect the photoluminescence data from the samples. ZnO nanoparticles showed a broad and stable emission peak at ∼570 nm, while a strongly quantum confined emission from PbS nanoparticles was detected at ∼1344-1486 nm. The ZnO-PbS nanocomposites exhibited dual emission in the visible and near-infrared (NIR) regions that is associated with defects and recombination of excitonic centres in the ZnO and PbS nanoparticles, respectively. The PL intensity of the visible emission from the ZnO-PbS nanocomposite was shown to increase when the ZnO to PbS molar ratio was 5:1 and the emission was almost quenched at molar ratios of 1:1 and 1:5. For different molar ratios of ZnO to PbS, the PL intensity of the NIR emission from the ZnO-PbS nanocomposites was more intense than that of PbS nanoparticles.     

Magnetic nanoparticles coated with carboxymethylated polysaccharide shells—Interaction with human cells

The interaction of magnetic core shell nanoparticles with living cells depends on the structure of the shell. In this paper we demonstrate a strong difference in the cell-nanoparticle interaction depending on the backbone of carboxymethylated polysaccharides used as shell material. Carboxymethyl cellulose with its β-1→4 linked structure and the carboxymethylated pullulan [α-1→6 linked maltotriose with α-1→4 linkages] show a constant interaction rate with both, tumor cells and leukocytes. In contrast, carboxymethyl dextran with a α-1→6 linked backbone exhibits a rapid interaction kinetic with tumor cells that is reduced with leukocytes as target.     

Influence of magnetic dipole and magnetoelastic interactions on the phase states of 2D non-Heisenberg ferromagnetic with complex exchange interactions

The phase states of the 2D non-Heisenberg ferromagnetic with anisotropic bilinear and biquadratic exchange interactions are investigated. The limiting cases of the system under consideration are the two-dimensional XY-model with biquadratic exchange interaction and the isotropic Heisenberg ferromagnetic. The account of the magnetic dipole interaction leads to the realization of spatially inhomogeneous quadrupolar phase. The stability regions of various phase transitions for different values of the material parameters are studied. The phase diagram is built. Besides, the temperature phase transitions are investigated. The influence of the magnetoelastic interaction on the formation of the long-range quadrupolar order is determined.     

Comparison of pulsed arterial spin labeling encoding schemes and absolute perfusion quantification

Arterial spin labeling (ASL) using magnetic resonance imaging (MRI) is a powerful noninvasive technique to investigate the physiological status of brain tissue by measuring cerebral blood flow (CBF). ASL assesses the inflow of magnetically labeled arterial blood into an imaging voxel. In the last 2 decades, various ASL sequences have been proposed which differ in their ease of implementation and their sensitivity to artifacts. In addition, several quantification methods have been developed to determine the absolute value of CBF from ASL magnetization difference images. In this study, we evaluated three pulsed ASL sequences and three absolute quantification schemes. It was found that FAIR-QUIPSSII implementation of ASL yields 10–20% higher signal-to-noise ratio (SNR) and 18% higher CBF as compared with PICORE-Q2TIPS (with FOCI pulses) and PICORE-QUIPSSII (with BASSI pulses). In addition, quantification schemes employed can give rise to up to a 35% difference in CBF values. We conclude that, although all quantitative ASL sequences and CBF calibration methods should in principle result in the similar CBF values and image quality, substantial differences in CBF values and SNR were found. Thus, comparing studies using different ASL sequences and analysis algorithms is likely to result in erroneous intra- and intergroup differences. Therefore, (i) the same quantification schemes should consistently be used, and (ii) quantification using local tissue proton density should yield the most accurate CBF values because, although still requiring definitive demonstration in future studies, the proton density of blood is assumed to be very similar to the value of gray matter.     

Perfusion in rat brain at 7 T with arterial spin labeling using FAIR-TrueFISP and QUIPSS

Measurement of perfusion in longitudinal studies allows for the assessment of tissue integrity and the detection of subtle pathologies. In this work, the feasibility of measuring brain perfusion in rats with high spatial resolution using arterial spin labeling is reported. A flow-sensitive alternating recovery sequence, coupled with a balanced gradient fast imaging with steady-state precession readout section was used to minimize ghosting and geometric distortions, while achieving high signal-to-noise ratio. The quantitative imaging of perfusion using a single subtraction method was implemented to address the effects of variable transit delays between the labeling of spins and their arrival at the imaging slice. Studies in six rats at 7 T showed good perfusion contrast with minimal geometric distortion. The measured blood flow values of 152.5±6.3 ml/100 g per minute in gray matter and 72.3±14.0 ml/100 g per minute in white matter are in good agreement with previously reported values based on autoradiography, considered to be the gold standard.     

树形分子包覆的ZnS量子点对潜指纹的荧光标记成像研究

在Zn2+离子与聚酰胺-胺(PAMAM)树形分子配位的基础上,制备了稳定的PAMAM树形分子包覆的ZnS量子点(quantum dots,QDs),并用紫外-可见吸收光谱(UV-Vis)和荧光发射光谱进行了表征。结果表明,Zn2+离子能与PAMAM树形分子发生配位络合作用,且饱和配位时间为6h;在波长365nm紫外光的激发下,PAMAM树形分子包覆的ZnS量子点发射出明亮的蓝色荧光,荧光发射峰约位于450nm。最后,将得到的PAMAM树形分子包覆的ZnS量子点纳米复合材料应用于锡纸上潜指纹的荧光标记成像研究,发现指纹可以被清晰识别,呈现明亮的蓝色荧光指纹。     

Effects of different parameters on thermal and mechanical properties of aminated graphene/epoxy nanocomposites connected by covalent: A molecular dynamics study

This paper is devoted to studying the thermal and mechanical properties of aminated graphene (AG)/epoxy nanocomposites connected by covalent bond using molecular dynamics (MD) simulation. The effects of crosslinking degree, mass fraction and functionalized graphene (FG) type on AG/epoxy nanocomposites are considered. The elasticity modulus (E), the glass transition temperature (T_g), the coefficient of thermal expansion (CTE) and the interfacial energy (E_int) are also investigated. The MD simulation results indicate that, when the mass fraction of AG is between 1.2% and 3.1% and crosslinking degree reaches about 70%, the E, T_g, E_int and CTE of AG/epoxy nanocomposites are significantly improved compared with those of pure epoxy and graphene/epoxy nanocomposites. The reason is that AG not only possesses some excellent thermodynamic properties of graphene, but also has the function of curing agent to crosslink with epoxy monomer to form the carbon-nitrogen (C–N) covalent bond. A better interfacial interaction between nanoparticles and epoxy is essential in enhancing the thermal and mechanical properties of nanocomposite materials, which will provide a microscopic theoretical basis for the study of epoxy nanocomposites.     

Effect of surface modification on dielectric and magnetic properties of metal powder/polymer nanocomposites

Metal nanopowder (Co and Fe)/polymer composites, both with and without surface modification by behenic acid, were fabricated and their dielectric and magnetic properties were measured at 1 GHz to study the effect of surface modification on the electromagnetic properties. The relative permittivity and the real part of the permeability of the composites with surface modified powders were higher than those with unmodified powders. Related dielectric losses remained at almost the same level, but magnetic losses were somewhat increased. The increase of relative permittivity could result from the increased volume fraction of interphase with a slightly higher relative permittivity at the particle/polymer interface than that of the bulk polymer. The increase in the real part of the permeability may be caused by suppression of the induced demagnetizing field due to suppression of eddy currents by a better particle distribution and a decrease in effective agglomerate size because of the surface modification.     

Electromagnetic wave absorption of polymeric nanocomposites based on ferrite with a spinel and hexagonal crystal structure

We have investigated composites designed for microwave absorption based on magnetic filler, composed of phases within the SrO-Fe₂O₃ system, embedded in a polyphenylene sulfide matrix with a concentration ratio of 80:20 by weight. The formation of the nanosized particles of SrFe₁₂O₁₉ and Fe₃O₄, as the principal magnetic phases was achieved via the co-precipitation of Sr²⁺/Fe³⁺ ions using different molar ratios. The various precursors obtained were calcined between 600 °C and 900 °C in air. The electromagnetic parameters of the composites were measured with a vector network analyzer at 400 MHz to 32 GHz. The results show that with a composite composed of a complex magnetic filler comprising the nanoparticles of two magnetically diverse phases, i.e., a spinel phase as the electromagnetic wave absorber in the lower GHz range and a hexagonal phase operating at a higher GHz range, above 32 GHz, a microwave absorber with an broad absorption range can be prepared.     

Many particle magnetic dipole-dipole and hydrodynamic interactions in magnetizable stent assisted magnetic drug targeting

The implant assisted magnetic targeted drug delivery system of Avilés, Ebner and Ritter is considered both experimentally (in vitro) and theoretically. The results of a 2D mathematical model are compared with 3D experimental results for a magnetizable wire stent. In this experiment a ferromagnetic, coiled wire stent is implanted to aid collection of particles which consist of single domain magnetic nanoparticles (radius ). In order to model the agglomeration of particles known to occur in this system, the magnetic dipole-dipole and hydrodynamic interactions for multiple particles are included. Simulations based on this mathematical model were performed using open source C++ code. Different initial positions are considered and the system performance is assessed in terms of collection efficiency. The results of this model show closer agreement with the measured in vitro experimental results and with the literature. The implications in nanotechnology and nanomedicine are based on the prediction of the particle efficiency, in conjunction with the magnetizable stent, for targeted drug delivery.