Mechanical manipulation of magnetic nanoparticles by magnetic force microscopy

A method has been developed in this work for the mechanical manipulation of magnetic nanoparticles (MNPs). A helical curve was designed as the capture path to pick up and remove the target nanoparticle on a mica surface by a magnetic probe based on the magnetic force microscope (MFM). There were magnetic, tangential and pushing forces acting on the target particle during the approaching process when the tip followed the helical curve as the capture path. The magnetic force was significant when the tip was closer to the particle. The target particle can be attached on the surface of the magnetic probe tip and then be picked up after the tip retracted from the mica surface. Theoretical analysis and experimental results were presented for the pick-up and removal of MNPs. With this method, the precision and flexibility of manipulation of MNPs were improved significantly compared to the pushing or sliding of the target object away from the corresponding original location following a planned path

Biomimetic route to hybrid nano-Composite scaffold for tissue engineering

Hydroxyapatite-poly(vinyl) alcohol-protein composites have been prepared by a biomimetic route at ambient conditions, aged for a fortnight at 30±2°C and given a shape in the form of blocks by thermal cycling. The structural characterizations reveal a good control over the morphology mainly the size and shape of the particles. Initial mechanical studies are very encouraging. Three biocompatibility tests, i.e., hemocompatibility, cell adhesion, and toxicity have been done from Shree Chitra Tirunal, Trivandrum and the results qualify their standards. Samples are being sent for more biocompatibility tests. Optimization of the blocks in terms of hydroxyapatite and polymer composition w.r.t the applications and its affect on the mechanical strength have been initiated. Rapid prototyping and a β-tricalcium – hydroxyapatite combination in composites are in the offing

Differences in magnetic particle uptake by CNS neuroglial subclasses: implications for neural tissue engineering

AIM: To analyze magnetic particle uptake and intracellular processing by the four main non-neuronal subclasses of the CNS: oligodendrocyte precursor cells; oligodendrocytes; astrocytes; and microglia. MATERIALS & METHODS: Magnetic particle uptake and processing were studied in rat oligodendrocyte precursor cells and oligodendrocytes using fluorescence and transmission electron microscopy, and the results collated with previous data from rat microglia and astrocyte studies. All cells were derived from primary mixed glial cultures. RESULTS: Significant intercellular differences were observed between glial subtypes: microglia demonstrate the most rapid/extensive particle uptake, followed by astrocytes, with oligodendrocyte precursor cells and oligodendrocytes showing significantly lower uptake. Ultrastructural analyses suggest that magnetic particles are extensively degraded in microglia, but relatively stable in other cells. CONCLUSION: Intercellular differences in particle uptake and handling exist between the major neuroglial subtypes. This has important implications for the utility of the magnetic particle platform for neurobiological applications including genetic modification, transplant cell labeling and biomolecule delivery to mixed CNS cell populations

Polymer vesicles (from virus to cell biomimicry)

Les polymersomes, obtenus par auto-assemblage en solution aqueuse de copolymères à blocs amphiphiles en structure vésiculaire, sont présentés comme d excellent mimes synthétiques des virus, dont les propriétés membranaires principalement élasticité, perméabilité, fonctionnalité- peuvent être très proches. Il y a ainsi un fort engouement quant à leur utilisation en biotechnologie et surtout en vectorisation d actifs pharmaceutiques ou cosmétiques. Afin d aller encore plus loin dans le biomimétisme ou la bio-inspiration, une étape devait être franchie : encapsuler ces polymersomes les uns dans les autres. Ce cloisonnement ou multi-compartimentalisation permet de mimer cette fois la structure d une cellule dite eukaryote, elle-même constituée de compartiments internes (organelles) et d un cytoplasme (lui conférant entre autres une certaine stabilité mécanique) contenues dans le compartiment externe représenté par la membrane cellulaire. Toutefois, l obtention d un simple mime structural d une structure si complexe représente déjà un challenge en soi, nécessitant maîtrise de la physico-chimie des systèmes, de la stabilisation des interfaces et des outils de formulation. Une méthode d émulsion-centrifugation a été développée et a permis d obtenir de telles structures compartimentalisées (mimes d organelles) à cavité gélifiée (mime de cytoplasme). Finalement, différentes voies d exploitation de ces systèmes sont présentées, allant de l encapsulation multiple, la libération contrôlée jusqu au développement de réactions enzymatiques en cascade confinées, mimant ainsi le métabolisme cellulaire.Amphiphilic block copolymers self-assemble in water into vesicles, coined polymersomes ; these vesicles are described as excellent synthetic mimics of viral capsids due to the resemblance of their respective membrane properties (in terms of elasticity, permeability, and functionality). As a result, they were massively investigated over the last years regarding applications in biotechnology and more particularly for the targeted delivery of pharmaceutical or cosmetic actives.In order to go further towards bio-inspiration and cell biomimicry, the next step required the encapsulation of polymersomes in other polymersomes. This multicompartmentalization indeed enables to mimic the structure of an eukaryotic cell; an outer cellular membrane compartment encloses internal compartments (organelles) and a cytoplasm responsible amongst others for a certain mechanic stability. However, alone the controlled formation of a system mimicking such a complex structure represents a technological challenge in terms of control over the physical chemistry of these systems, the stabilization of their interfaces and their formulation. A formation method based upon an emulsion-centrifugation has been developed and enabled the formation of such multicompartmentalized structures (organelle mimics) with a gelified lumen (cytoplasm mimic). Finally, various potential applications of these systems are presented: from multiple encapsulation, controlled drug release, to the development of enzymatic and confined cascade reactions that mimick the cellular metabolism.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF

Encapsulamento de nanopartículas à base de óxido de ferro com sílica para aplicações biomédicas

Over last decades, a great attention has been devoted to iron oxide-based nanoparticles coated by dielectric organic or inorganic materials for the potential contributions in biomedical applications and microwave absorbers industry. The present Ph.D. study focuses on the fabrication of iron-based oxide nanoparticles and coating the particles within the silica matrix in the form of a core-shell structure exhibiting interesting magnetic and electrical properties for application in the biomedical and microwave technology areas. The combined study of electrical and magnetic properties of the silica-iron oxide composites allowed us to examine the requisites for application in a new generation of the high-efficient microwave absorbents and also for the possibility of hyperthermia and drug delivery agents. In this context, four synthesis methods: sol-gel route, laser floating zone (LFZ), auto-combustion, and Pechini method were employed to prepare the iron oxide-based/silica composites. Several studies, namely, structural, morphological, electrical and magnetic characterizations, were performed on the prepared samples. The utilization of several experimental characterizing techniques not only provide us a comprehensive knowledge of the physical properties of these materials but also look over the future employment of the prepared composites in the biomedical application and the microwave absorbing materials. It was prepared a series of glasses with the composition, xFe2O3-(100-x)SiO2 (x=1, 2, 10, 20 in mol%) by the sol-gel route. The effect of the heat treatment conditions and the Fe/Si ratio on the morphology, electrical and magnetic properties of the glass ceramics were investigated. Fibers with the composition of 10Fe2O3-90SiO2 were processed by LFZ technique. Their morphology, structure, magnetic properties and redox state were studied in function of the pulling rate. An exhautive study on the Raman spectroscopy and the local magnetic microstructure of the fibers were performed to support for a deeper understanding of the magnetic properties of the fibers. A series of manganese ferrite-silica nanocomposites with the composition xMnFe2O4-(100-x)SiO2 (x=100, 20, 15 and 10 in mol%) were prepared by the auto combustion method. The physical parameters obtained from this study showed the great potential of the silica-manganese ferrite nanocomposites for the proposed applications as well other suggested future works. In addition, a preliminary study on the synthesis by the Pechini method and characterization of iron oxide was carried out. The structure, the magnetic properties and the electric conduction mechanism of the prepared iron oxide polycrystallites were investigated leaving open other possible applications industries.Nas últimas décadas grande atenção tem sido dedicada ao estudo de nanopartículas à base de óxido de ferro revestidas por materiais dielétricos orgânicos ou inorgânicos com potencial para aplicações biomédicas e na indústria de absorventes de microondas. O presente trabalho de doutoramento centra-se na fabricação de nanopartículas de óxido de ferro e no seu revestimento com sílica na forma de uma estrutura núcleo-casca com o objectivo de obter propriedades magnéticas e elétricas interessantes para aplicações práticas na área biomédica e na indústria de microondas. O estudo combinado das propriedades elétricas e magnéticas dos compósitos de óxido de ferro-sílica permitiu estudar as características para aplicações em nova geração de absorventes de micro-ondas de alta eficiência e também agentes com possíveis utilizações em hipertermia e libertação de drogas. Neste contexto foram utilizados, quatro métodos de síntese: método de sol-gel, técnica fusão de zona flutuante com laser (LFZ), autocombustão e método de Pechini na preparação dos compósitos à base de óxido de ferro / sílica. Vários estudos como caracterização estrutural, morfológica, elétrica e magnética, foram realizados nas amostras preparadas. A utilização de várias técnicas de caracterização experimental fornece um conhecimento abrangente das propriedades físicas destes materiais e permite perspectivar o possível emprego destes compósitos para aplicações biomédicas e como materiais absorventes de micro-ondas no futuro. Foi preparada a série de vidros xFe2O3- (100-x) SiO2 (x = 1, 2, 10, 20 em mol%) pelo método de rota sol-gel. O efeito das condições de tratamento térmico e da relação Fe / Si na morfologia, propriedades elétricas e magnéticas das cerâmicas vítreas foi investigado. Fibras com a composição 10Fe2O3-90SiO2 foram processadas pela técnica de LFZ. A sua morfologia, estrutura, propriedades magnéticas e estado de redução foram estudadas em função da taxa de extração da preparação das amostras. Foi realizada uma análise exaustiva dos resultados da espectroscopia de Raman e uma pesquisa da microestrutura magnética local para melhor interpretar as características magnéticas das fibras. Uma série de nanocompósitos de silício-ferrite de manganês com a composição xMnFe2O4- (100-x) SiO2 (x = 100, 20, 15 e 10 em % molar) foi preparada pelo método de auto-combustão. Foi realizada investigação das propriedades estruturais, morfológicas, elétricas e magnéticas destas amostras. Os parâmetros físicos obtidos a partir desse estudo mostraram o grande potencial dos nanocompósitos de silício-ferrita de manganês para as aplicações propostas assim como para o trabalho futuro sugerido. Além disso, também foi realizado um estudo preliminar sobre a síntese e caracterização do óxido de ferro pelo método de Pechini.A estrutura, as propriedades magnéticas, o mecanismo de condução elétrica das policristalitas de óxido de ferro preparados foram realizadas deixando em aberto outras possíveis aplicações industriais.Programa Doutoral em Engenharia Físic

The Fifteenth Annual Conference YUCOMAT 2013: Programme and the Book of Abstracts

The First Conference on materials science and engineering, including physics, physical chemistry, condensed matter chemistry, and technology in general, was held in September 1995, in Herceg Novi. An initiative to establish Yugoslav Materials Research Society was born at the conference and, similar to other MR societies in the world, the programme was made and objectives determined. The Yugoslav Materials Research Society (Yu-MRS), a nongovernment and non-profit scientific association, was founded in 1997 to promote multidisciplinary goal-oriented research in materials science and engineering. The main task and objective of the Society has been to encourage creativity in materials research and engineering to reach a harmonic coordination between achievements in this field in our country and analogous activities in the world with an aim to include our country into global international projects. Until 2003, Conferences were held every second year and then they grew into Annual Conferences that were traditionally held in Herceg Novi in September of every year. In 2007 Yu-MRS formed two new MRS: MRS-Serbia (official successor of Yu-MRS) and MRS-Montenegro (in founding). In 2008, MRS – Serbia became a member of FEMS (Federation of European Materials Societies)

FWP executive summaries, Basic Energy Sciences Materials Sciences Programs (SNL/NM)

The BES Materials Sciences Program has the central theme of Scientifically Tailored Materials. The major objective of this program is to combine Sandia`s expertise and capabilities in the areas of solid state sciences, advanced atomic-level diagnostics and materials synthesis and processing science to produce new classes of tailored materials as well as to enhance the properties of existing materials for US energy applications and for critical defense needs. Current core research in this program includes the physics and chemistry of ceramics synthesis and processing, the use of energetic particles for the synthesis and study of materials, tailored surfaces and interfaces for materials applications, chemical vapor deposition sciences, artificially-structured semiconductor materials science, advanced growth techniques for improved semiconductor structures, transport in unconventional solids, atomic-level science of interfacial adhesion, high-temperature superconductors, and the synthesis and processing of nano-size clusters for energy applications. In addition, the program includes the following three smaller efforts initiated in the past two years: (1) Wetting and Flow of Liquid Metals and Amorphous Ceramics at Solid Interfaces, (2) Field-Structured Anisotropic Composites, and (3) Composition-Modulated Semiconductor Structures for Photovoltaic and Optical Technologies. The latter is a joint effort with the National Renewable Energy Laboratory. Separate summaries are given of individual research areas

Magnetic force imaging and handling of cancer cells on the nanoscale

A thesis submitted to the University of Bedfordshire in partial fulfilment of the requirements for the degree of Doctor of PhilosophyCancer treatment has become one of the top priorities in health. Great efforts have been devoted to the diagnosis and therapy of cancers. Culturing cells with drugs is a common method used to investigate cancer therapy in experiments. However, this method has limitations in cancer treatment because of the lack of capabilities of handling cells, targeting specific cells and measuring the nanoscale changes in cell structures. Magnetic nanoparticles (MNPs) and magnetic force microscopes (MFMs) have been used to study biological samples due to their advantages in tracing, manipulating and measuring, which has motivated to research the method for implanting MNPs into cancer cells, to target the cancer cells and to measure their changes during the treatment. Research reported in this thesis focuses on magnetic force imaging and handling of targeted cancer cells on the nanoscale for possible new cancer therapies. A new differential MFM imaging method and a new compensation MFM imaging method were developed in this research to improve the MFM imaging quality. The former reverses the magnetized direction of probe from upward to downward and the latter scans the samples with three scanning directions of 0°, 45° and 90°. With these methods, the obtained MFM images achieve a high resolution, SNR, image contrast and accuracy. A pair of innovative MNPs picking up method and MNPs releasing method were developed in this research to achieve flexible MNPs picking up and releasing. The picking up method handles the magnetic tip following a helical structure as the capture path when approaching to the target MNPs. The MNPs releasing method uses a biaxiably-oriented polypropylene (BOPP) film together with a magnet allowing MNPs to separate from the MFM tip surface. With these methods, the target MNPs can be picked up by the MFM tip and released from the tip surface successfully. This research discovered, for the first time in the world to the author knowledge, the differences in morphological features (height, length, width and roughness) and mechanical properties (adhesive force and Young‟s modulus) between multinuclear and mononuclear colon cancer cells after treating the cells with fullerenol. This discovery provides guidance to the selection of cells for target treatment. The results indicate that the mononuclear SW480 cells are more sensitive to fullerenol than the multinuclear SW480 cells and the multinuclear SW480 cells exhibit a stronger drug-resistance than the mononuclear SW480 cells. A new MNPs implantation method was developed in this research, which enables the FITC-MNPs functioned tip to insert into cells so that MNPs are implanted into the target cells. Fluorescence microscope images show that the FITC-MNPs are released into the cells successfully. Cells being treated with MNPs (Cell-MNPs) manipulation III methods are explored by magnet and controllable electromagnets to manipulate the target cancer cells. The results show that the cell-MNPs have magnetic force manipulated capability and they can be manipulated to have the leftward, rightward, upward and downward flexibilities

Development of a micro-Hall magnetometer and studies of individual Fe-filled carbon nanotubes

This work presents Hall magnetometry studies on individual Fe-filled carbon nanotubes (CNT). For this approach high sensitivity micro Hall sensors based on a GaAs/AlGaAs heterostructure with two dimensional electron gas (2DEG) were developed. Electron beam lithography and wet chemical etching were utilized for patterning Hall sensors onto the heterostructure surface. The devices were characterized by means of scanning electron microscopy, atomic force microscopy and transport measurements. Individual Fe-filled CNTs were placed on active part of devices (800 × 800 nm2) with aid of micromanipulator system. Measurements on an individual iron nanowires confirmed devices applicability for measurements of nanoscale magnets. High nucleation fields were found of about 900 mT for a Fe nanowire with diameter of d = 26 nm. The magnetization reversal mechanism was found to be a localized process whereas the angular dependence of nucleation fields is in a good agreement with a curling mode. Through magnetization studies performed on differently functionalized ensembles of CNT by means of Alternating Gradient – and Superconducting Quantum Interference Device (SQUID) magnetometry a strong influence of a remaining ferromagnetic catalyst material on the magnetic properties of CNT was observed. Magnetization studies proved that a post annealing method removes catalyst material completely