Bifunctional CoFe2O4/ZnO Core/Shell Nanoparticles for Magnetic Fluid Hyperthermia with Controlled Optical Response

Conjugation of optical and magnetic responses in a unique system at the nanoscale emerges as a powerful tool for several applications. Here, we fabricated bifunctional CoFe2O4-core/ZnO-shell nanoparticles with simultaneous photoluminescence in the visible range and ac magnetic losses suitable for hyperthermia. The structural characterization confirms that the system is formed by a ≈7 nm CoFe2O4 core encapsulated in a ≈1.5-nm-thick semiconducting ZnO shell. As expected from its high anisotropy, the magnetic losses in an ac magnetic field are dominated by the Brown relaxation mechanism. The ac magnetic response of the core/shell system can be accurately predicted by the linear response theory and differs from that one of bare CoFe2O4 nanoparticles as a consequence of changes in the viscous relaxation process due to the effect of the magnetostatic interactions. Concerning the optical properties, by comparing core/shell CoFe2O4/ZnO and single-phase ZnO nanoparticles, we found that the former exhibits a broader optical absorption and photoluminescence, both shifted to the visible range, indicating that the optical properties are closely associated with the shell-morphology of ZnO. Being focused on bifunctional nanoparticles with an optical response in the visible range and a tunable hyperthermia output, our results can help to address current open questions on magnetic fluid hyperthermia.Fil: Lavorato, Gabriel Carlos. Centro Brasileiro de Pesquisas Físicas; Brasil. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Lima, Enio Junior. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Vasquez Mansilla, Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Troiani, Horacio Esteban. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Zysler, Roberto Daniel. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Winkler, Elin Lilian. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentin

Co-precipitation synthesis of stable iron oxide nanoparticles with NaOH: New insights and continuous production via flow chemistry

Co-precipitation is by far the most common synthesis for magnetic iron oxide nanoparticles (IONPs), as cheap and environmentally friendly precursors and simple experimental procedures facilitate IONP production in many labs. Optimising co-precipitation syntheses remains challenging however, as particle formation mechanisms are not well understood. This is partly due to the rapid particle formation (within seconds) providing insufficient time to characterise initial precipitates. To overcome this limitation, a flow chemistry approach has been developed using steady-state operation to “freeze” transient reaction states locally. This allowed for the first time a comprehensive analysis of the early stages of co-precipitation syntheses via in-situ Small Angle X-ray Scattering and in-situ synchrotron X-Ray Diffraction. These studies revealed that after mixing the ferrous/ferric chloride precursor with the NaOH base solution, the most magnetic iron oxide phase forms within 5 s, the particle size changes only marginally afterwards, and co-precipitation and agglomeration occur simultaneously. As these agglomerates were too large to achieve colloidal stability via subsequent stabiliser addition, co-precipitated IONPs had to be de-agglomerated. This was achieved by adding the appropriate quantity of a citric acid solution which yielded within minutes colloidally stable IONP solutions around a neutral pH value. The new insights into the particle formation and the novel stabilisation procedure (not requiring any ultra-sonication or washing step) allowed to design a multistage flow reactor to synthesise and stabilise IONPs continuously with a residence time of less than 5 min. This reactor was robust against fouling and produced stable IONP solutions (of ~1.5 mg particles per ml) reproducibly via fast mixing ( 500 ml/h) for low materials cost

Bioinspired synthesis and characterization of organic/inorganic nanocomposite materials

In Nature, hybrid materials with hierarchical structure are formed by biomineralization of organic macromolecules that act as templates for the nucleation and/or growth of the inorganic component. The building blocks of the natural organic macromolecules provide the template architectures that result in chemical and morphological diversity in the inorganic phases. Inspired by the formation of biominerals in living organisms, novel organic-inorganic hybrid materials have been designed and developed by biomimetic routes. There is a growing interest in using synthetic polymers, engineered proteins, and various polymer-based hybrid architectures as templates for bioinspired synthesis. In this work, we have used amphiphilic block copolymers as well as block copolymer-protein conjugates that undergo hierarchical self-assembly to form nanoscale micelles and macroscale gels as templates for controlled nanocomposite formation within the polymeric matrix. The amphiphilic block copolymers that were generated based on Pluronics are unique systems that can reversibly self-assemble into macroscale elastic solids in solution, based on pH and temperature changes. The efforts were focused on three systems--calcium phosphate nanocomposites, zirconia nanocomposites, and magnetic nanocomposites. We have developed a robust method with control over the formation as well as placement of an inorganic phase in the nanocomposite structure, for a variety of different inorganic nanoparticles, such as calcium phosphate, zirconia and magnetic nanoparticles. The future work will be focused on using biominerlization proteins to create functional dynamic magnetic materials and nanostructures both in solution and on surfaces

Synthesis and Functionalization of Iron Oxide Nanoparticles and their Application in Hybrid Materials

Nanomaterials have been in the center of interest for several decades now, and the number of publications and applications still grows. However, there are many aspects of nanoparticle formation and behavior still unknown. In particular, the coordination of ligands onto a particle surface holds many questions because of the intermediate states of nanoparticles, lying between bulk and molecule-like behavior. In this work, two synthetic methods were used to make spherical and spindle-shaped particles of different iron oxides. Strongly magnetic maghemite (γ-Fe2O3) spheres were used as a model system to investigate the binding of the surfactant molecules oleic acid, 3,4- dihydroxyhydrocinamic acid and tetramethylammonium hydroxide. Here the focus was on the nature of the exchange of one ligand against another one. The magnetic properties inside solid polymer matrices were investigated with particles of different functionalization in PMMA and polydopamineacrylate (PDAm). Particles incorporated in PDAm exhibited interesting changes in the magnetic moment which resulted from a chemical reaction of the polymer bound to the particle and forming a shell with opposite magnetic moment. Such chemically controllable magnetism might be applied in data storage and switchable technologies. Weakly ferromagnetic spindle-shaped hematite (α-Fe2O3) particles were synthesized using variable reaction parameters. This research was meant to show how these parameters affect the length and the aspect ratio of the particles. The particles were used to make mesogenic phases in polyethylene glycol (400) as a solvent. The orientation of the lyotropic liquid crystal phase could be directed by an external magnetic field. The flow of light can thus be directed magnetically. Furthermore, different concentrations of hematite particles were embedded in polyvinyl alcohol via an electrospinning process and their peroxidase-like behavior and wound healing properties were probed. The particles inside the fiber meshes catalytically convert reactive H2O2 to H2O and O2 and thus promote the healing process of skin tissue. This composite offers a cheap and easy way to produce band-aids for wound treatment.131 Seiten, Illustrationen, Diagramm

Nonaqueous Synthesis of Metal Oxide Nanoparticles and Their Surface Coating

This thesis mainly consists of two parts, the synthesis of several kinds of technologically interesting crystalline metal oxide nanoparticles via high temperature nonaqueous solution processes and the formation of core-shell structure metal oxide composites using some of these nanoparticles as the core with silica, titania or polymer as shell via a modified microemulsion approach. In the first part, the experimental procedures and characterization results of successful synthesis of crystalline iron oxide (Fe3O4) and indium oxide (In2O3) nanoparticles are reported. Those nanoparticles exhibit monodispersed particle size, high crystallinity and high dispersibility in non-polar solvents. The particle size can be tuned by the seed mediated growth and the particle shape can also be controlled by altering the capping ligand type and amount. The mixed bi-metal oxides such as cobalt iron oxide and lithium cobalt oxide will be discussed as well. In the second part, the synthesis and characterization of various surface coated metal oxides, including silica, titania and polymer coated nanocomposites are reported. The silica coating process is presented as a highlight of this part. By using a microemulsion system, core-shell structure silica coated iron oxide and indium oxide nanocomposites are successfully prepared. Furthermore, the thickness of the silica coating can be controlled from 2 nm to about 100 nm by adjusting the reaction agents of the micelle system. By extending the procedure, we will also discuss the titania and polymer coating preparation and characterization

Mineralogy

Mineralogy - Significance and Applications includes new contributions to the field of mineralogy in terms of mineral chemistry and petrogenesis using updated facilities from regions in Asia and Europe to interpret petrologic significance. It discusses the industrial uses of some minerals as raw materials and in electrical firms and gemology. The book also introduces several works on synthesis of some compounds and applications of mineralogy in biomedicine, including iron oxide nanoparticles and nannocomposites, and their biomedical applications as diagnostic and drug delivery tools for treatment of cancer and many other diseases

Engineering Porous Silicon for a Top-Down Approach to Controlled Drug Delivery

Nanocarriers that localize a therapeutic to a disease site and release it “on-demand” via the clinician’s control will mitigate the adverse effects that reduce a patient’s quality of life while undergoing oncology treatment. Moreover, magnetically actuated drug delivery carriers are appealing platforms in next-generation targeted medicine, yet these carriers must be compatible with scalable fabrication techniques to realize their clinical translation. In this dissertation, a magnetically capped porous silicon nanocomposite (APTESPSi@Fe3O4), that responds to physiologically relevant temperatures, was developed using cost-effective, highly scalable methods such as electrochemical etching. Fourier transform infrared spectroscopy (FTIR), CHNS elemental analysis, and zeta potential confirmed that accelerated hydrolysis at 45 �C altered the porous silicon surface chemistry. This hydrolysis-mediated electrostatic degradation between the porous silicon and Fe3O4 caps translated to a thermoresponsive release behavior in dissolution studies with sorafenib (SFN), where minimal drug was released at room temperature and 37 �C, while an enhanced release occurred at 45 �C and 50 �C. The magnetic heat dissipation capabilities with application of an alternating magnetic field (AMF) was calculated by the specific absorption rate (SAR) through calorimetry and magnetic susceptibility measurements. Comparing these two methods revealed that the electrostatic interactions between the porous silicon and Fe3O4 do not hinder the Brownian relaxation and heat dissipation. The nanocomposite and its components demonstrated high cytocompatibility after 24 hours with RAW 246.7, MDA-MB-231, and HepG2 cells, but not with MCF-7. High cytocompatibility was also observed when the cells incubated with particles were heated to 45 �C for 15 min followed by 37 �C for the remaining 6 hour incubation period. Porous silicon and its nanocomposite improved the SFN solubility in in vitro studies with MDA-MB-231 and HepG2, resulting in increased anticancer activity in comparison to the free drug. Moreover, the anticancer activity was readily controlled from the magnetic nanocomposite by modulating the amount of SFN released with temperature. Confocal microscopy and flow cytometry showed a higher uptake of the amine-modified porous silicon in comparison to the magnetic nanocomposite in MDA-MB-231 cells. The temperature increase to 45 �C showed a reduced particle uptake, yet future studies monitoring the fluorescence from the free drug rather than the nanocarrier will prove useful. This novel system has laid the groundwork for a promising tool for clinicians to lessen the burden that millions of cancer patients face as they receive treatment

Synthesis, Biofunctionalization, and Application of Magnetic Nanomaterials

Since their inception in the late 1970\u27s magnetic nanomaterials have sparked heavy research into their use in the biomedical field. Their unique magnetic properties allow the magnetic particles to be the base for a large array of expiremental medical techniques, from treatments of disease, diagnostic tests, imaging aids, and more. In this manuscript, each stage starting from novel particle synthesis, functionalization with bioactive molecules, and innovative application is explored, specifically using the techniques magnetically mediated energy delivery, magnetophoresis, magnetic resonance imaging. The reproducible synthesis of nanomaterials is necessary if any further engineering application is going to be done. Using a novel extended LaMer approach where a precursor solution is consistently added to a reaction vessel allows for the linear volume growth of nanoparticles. This technique was originally used for the synthesis of magnetite (a simple ferrite) to control the volume of the particle indefinitely. Transferring it to a nonstoichiometric cobalt ferrite, it is shown that a linear volume growth is achieved up to 20nm. Secondary functionality of the magnetic particles has really opened up the application to sensing, selective treatment, and functional imaging. Surface modification with a bacterial strain discriminatory glycan allows for strain selective treatment of bacterial infection. Heparin functional particles show high pharmacokinetic activity for the treatment of neointimal hyperplasia due to high surface area to volume ratios. Gadolinium coated particles have distance dependent effects on the MRI relaxation rate of water, which may prove useful in functional imaging. Each of these complexes shows promise as a new way to treat or image malady. Although a small part in the large picture in developing a new generation of medicine, this research lays the foundation for each of these possible treatments. Be it the eradication of bacterial infection or the non-toxic prevention of restenosis, novel multifunctional nanomaterials such as the ones discussed in this manuscript, will be heavily relied on in the future of medicine

Heat dissipation in Sm3+ and Zn2+ co-substituted magnetite (Zn0.1SmxFe2.9-xO4) nanoparticles coated with citric acid and pluronic F127 for hyperthermia application

In this work, Sm3+ and Zn2+ co-substituted magnetite Zn0.1SmxFe2.9-xO4 (x = 0.0, 0.01, 0.02, 0.03, 0.04 and 0.05) nanoparticles, have been prepared via co-precipitation method and were electrostatically and sterically stabilized by citric acid and pluronic F127 coatings. The coated nanoparticles were well dispersed in an aqueous solution (pH 5.5). Magnetic and structural properties of the nanoparticles and their ferrofluids were studied by different methods. XRD studies illustrated that all as-prepared nanoparticles have a single phase spinel structure, with lattice constants affected by samarium cations substitution. The temperature dependence of the magnetization showed that Curie temperatures of the uncoated samples monotonically increased from 430 to 480 °C as Sm3+ content increased, due to increase in A-B super-exchange interactions. Room temperature magnetic measurements exhibited a decrease in saturation magnetization of the uncoated samples from 98.8 to 71.9 emu/g as the Sm3+ content increased, which is attributed to substitution of Sm3+ (1.5 µB) ions for Fe3+ (5 µB) ones in B sublattices. FTIR spectra confirmed that Sm3+ substituted Zn0.1SmxFe2.9-xO4 nanoparticles were coated with both citric acid and pluronic F127 properly. The mean particle size of the coated nanoparticles was 40 nm. Calorimetric measurements showed that the maximum SLP and ILP values obtained for Sm3+ substituted nanoparticles were 259 W/g and 3.49 nHm2/kg (1.08 mg/ml, measured at f = 290 kHz and H = 16kA/m), respectively, that are related to the sample with x = 0.01. Magnetic measurements revealed coercivity, which indicated that hysteresis loss may represent a substantial portion in heat generation. Our results show that these ferrofluids are potential candidates for magnetic hyperthermia applications

Effects of organic polymer addition in magnetite synthesis on its crystalline structure

Magnetite (Fe3O4) nanoparticles and magnetite-based inorganic–organic hybrids are attracting attention in biomedical fields as thermoseeds for hyperthermia and a contrast medium in magnetic resonance imaging. Size control of Fe3O4 thermoseeds is important as the particle size affects the heat generation properties. Fe3O4 can be easily synthesized via aqueous processes and the presence of organic substances during synthesis can affect the size and crystalline phase of the Fe3O4 formed. In this study, various polymers with different functional groups and surface charges were added to the precursor solution of Fe3O4 to clarify the relationship between the chemical structure of the organic substances and the crystal structure of Fe3O4. At first, coexistence effects of the organic substances in the solutions were clarified. As a result, crystalline Fe3O4 was precipitated even after addition of neutral polyethylene glycol and cationic poly(diallyldimethylammonium chloride). The poly(sodium-4-styrene sulfonate) addition significantly decreased the particle size, while polyacrylic acid addition inhibited Fe3O4 nucleation to afford an amorphous phase. These differences were related to the ease of complex formation from iron ions and coexisting organic polymers. In order to clarify this assumption, a modified experimental procedure was applied for the polyacrylic acid. Namely, the iron oxide precipitation by the NaOH solution was followed by the polyacrylic acid addition. Notably, Fe3O4 nucleation was not inhibited. Hence, the size and crystalline phase of the iron oxide prepared by the aqueous process were drastically affected by organic polymers