Input of Microwaves for Nanocrystal Synthesis and Surface Functionalization Focus on Iron Oxide Nanoparticles
Fundamentals and Applications, 2013
ABSTRACT
nm-Semiconductor Particles and Molecular Aggregates as Redox Species
Fine Particles Science and Technology, 1996
It is well established that the electronic levels in semiconductors shift when the latter are pre... more It is well established that the electronic levels in semiconductors shift when the latter are prepared in the form of nm-size particles [1]. Correspondingly the optical behavior of such small particles depends on their size and shape. One can expect that the redox behavior will also change with the size of nm-particles. Knowledge in the latter field is still in an infant state. In this paper experiments will be discussed that shed some light on the redox behavior of nm-semiconductor particles, firstly as donors in the excited electronic state and secondly as electron acceptors. Transport of excess charge carriers through a chain of nm- size semiconductor particles will be briefly discussed since this latter process is important for some of the suggested device applications for nm- particles. Presently available experimental results concerning electron transfer with semiconducter nm-particles suffer from the fact that the detailed structure and chemical nature of the interface is not really known for these systems. The experimental systems are complicated and the measurements can suffer from systematic faults. Experimental results obtained at closely related systems can serve as guidelines, e.g. electron transfer measurements on covalently linked molecular donor-spacer-acceptor systems and on quantum well-barrier-quantum well systems. Progress in this field appears highly desirable, since very interesting practical applications have been suggested for systems prepared from nm-size semiconductor particles involving electron transfer reactions and electron transport. Some of these systems have shown promising features. One prominent example is an electrode prepared from nm-size anatase TiO2 colloidal particles. This electrode is prepared with nm-particles that retain to a large degree their individual properties but are glued together such that they can facilitate efficient transport of excess charge carriers.
A bone targeting nanosystem is reported here which combined magnetic contrast agent for Magnetic ... more A bone targeting nanosystem is reported here which combined magnetic contrast agent for Magnetic Resonance Imaging (MRI) and a therapeutic agent (bisphosphonates) into one drug delivery system. This new targeting nanoplatform consists of superparamagneticγFe2O3nanoparticles conjugated to 1,5-dihydroxy-1,5,5-tris-phosphono-pentyl-phosphonic acid (di-HMBPs) molecules with a bisphosphonate function at the outer of the nanoparticle surface for bone targeting. The as-synthesized nanoparticles were evaluated as a specific MRI contrast agent by adsorption study onto hydroxyapatite and MRI measurment. The strong adsorption of the bisphosphonates nanoparticles to hydroxyapatite and their use as MRIT2∗contrast agent were demonstrated. Cellular tests performed on human osteosarcoma cells (MG63) show thatγFe2O3@di-HMBP hybrid nanomaterial has no citoxity effect in cell viability and may act as a diagnostic and therapeutic system.
Size-Dependent Nonlinear Weak-Field Magnetic Behavior of Maghemite Nanoparticles
Small, 2012
The magnetic behavior at room temperature of maghemite nanoparticles of variable sizes (from 7 to... more The magnetic behavior at room temperature of maghemite nanoparticles of variable sizes (from 7 to 20 nm) is compared using a conventional super quantum interference device (SQUID) and a recently patented technology, called MIAplex. The SQUID usually measures the magnetic response versus an applied magnetic field in a quasi-static mode until high field values (from -4000 to 4000 kA m(-1)) to determine the field-dependence and saturation magnetization of the sample. The MIAplex is a handheld portable device that measures a signal corresponding to the second derivative of the magnetization around zero field (between -15 and 15 kA m(-1)). In this paper, the magnetic response of the size series is correlated, both in diluted and powder form, between the SQUID and MIAplex. The SQUID curves are measured at room temperature in two magnetic field ranges from -4000 to 4000 kA m(-1) (-5T to 5T) and from -15 to 15 kA m(-1). Nonlinear behavior at weak fields is highlighted and the magnetic curves for diluted solutions evolve from quasi-paramagnetic to superparamagnetic behavior when the size of the nanoparticles increases. For the 7-nm sample, the fit of the magnetization with the Langevin model weighted with log-normal distribution corresponds closely to the magnetic size. This confirms the accuracy of the model of non-interacting superparamagnetic particles with a magnetically frustrated surface layer of about 0.5 nm thickness. For the other samples (10-nm to 21-nm), the experimental weak-field magnetization curves are modeled by more than one population of magnetically responding species. This behavior is consistent with a chemically uniform but magnetically distinct structure composed of a core and a magnetically active nanoparticle canted shell. Accordingly the weak-field signature corresponds to the total assembly of the nanoparticles. The impact of size polydispersity is also discussed.
We report the elaboration of new l-Proline functionalized superparamagnetic iron oxide nanopartic... more We report the elaboration of new l-Proline functionalized superparamagnetic iron oxide nanoparticles that can act as a new enantioselective organocatalyst. Boc-l-Proline and Fmoc-l-Proline are grafted using two different methodologies on a nanoplateform constituted of 10 nm maghemite (␥-Fe 2 O 3) nanoparticle stabilized by bidendate coating agent Alendronate. We show that coupling is far more efficient using microwave assisted methodology and that only Fmoc deprotection is compatible with our nanoplatform. Moreover the fluorenyl group is used for indirect quantification of grafted Proline onto nanoparticles.
Rings and Hexagons Made of Nanocrystals: A Marangoni Effect
The Journal of Physical Chemistry B, 2000
By controlling solvent evaporation rates, it has been possible to form micrometer rings and hexag... more By controlling solvent evaporation rates, it has been possible to form micrometer rings and hexagonal arrays made of nanocrystals of different sizes, shapes and materials. Such patterns are driven by surface tension gradients that induce Bénard-Marangoni ...
Synthesis of Silver Nanoparticles for the Dual Delivery of Doxorubicin and Alendronate to Cancer Cells
We describe an innovative multimodal system, which combines magnetic targeting of therapeutic age... more We describe an innovative multimodal system, which combines magnetic targeting of therapeutic agents with both magnetic resonance and fluorescence imaging into one system. This new magnetic nanoplatform consists of superparamagnetic γFe(2)O(3) nanoparticles, used clinically as an MRI contrast agent, conjugated to therapeutic molecules of the hydroxylmethylene bisphosphonate family (HMBPs): alendronate with an amine function as the terminal group. In vitro tests with breast cancer cells show that the γFe(2)O(3)@alendronate hybrid nanomaterial reduces cell viability and acts as a drug delivery system. We also investigated the anti-tumoural properties in vivo in nude mice xenografted with MDA-MB-231 tumours. We show that the presence of both γFe(2)O(3)@alendronate and a magnetic field significantly reduced the development of tumours. The amine functionalities can be used as precursor groups for the covalent coupling of peptides or monoclonal antibodies for specific biological targeting. The feasibility of this process was demonstrated by coupling rhodamine B, a fluorescence marker, to the γFe(2)O(3)@alendronate nanohybrid. The system showed fluorescent properties and high affinity for cells. Flow cytometry and fluorescence microscopy were used to study the kinetics of γFe(2)O(3)@alendronate uptake by cells. The magnetic and fluorescent nanoparticles are potential candidates for smart drug-delivery systems. Also, the superparamagnetic behaviour of such nanoparticles may be exploited as MRI contrast agents to improve therapeutic diagnostics.
Magneto-optic Response of Functionalized vs. Uncoated Fe2O3 (Maghemite) Nanoparticles
Magnetic and fluorescent assemblies of iron-oxide nanoparticles (NPs) were constructed by threadi... more Magnetic and fluorescent assemblies of iron-oxide nanoparticles (NPs) were constructed by threading a viologen-based ditopic ligand, DPV 2 + , into the cavity of cucurbituril (CB[7]) macrocycles adsorbed on the surface of the NPs. Evidence for the formation of 1:2 inclusion complexes that involve DPV 2 + and two CB[7] macrocycles was first obtained in solution by 1 H NMR and emission spectroscopy. DPV 2 + was found to induce self-assembly of nanoparticle arrays (DPV 2 + &CB[7]NPs) by bridging CB[7] molecules on different NPs. The resulting viologen-crosslinked iron-oxide nanoparticles exhibited increased saturation magnetization and emission properties. This facile supramolecular approach to NP self-assembly provides a platform for the synthesis of smart and innovative materials that can achieve a high degree of functionality and complexity and that are needed for a wide range of applications.
Iron oxide (g-Fe 2 O 3 ) nanoparticles (NPs) were efficiently coated with the water soluble macro... more Iron oxide (g-Fe 2 O 3 ) nanoparticles (NPs) were efficiently coated with the water soluble macrocycle cucurbit [7]uril (CB[7]) by microwave heating. Density functional theory (DFT) calculations support a binding model in which the carbonyl oxygens of CB[7] coordinate directly to surface Fe 3+ ions. The modified particles (CB [7]NPs) are stable under a wide pH range (2-12) and have a transverse relaxivity, R 2 , of 113 s À1 mM À1 . Nile red (NR) dye was loaded into the cavities of the surface-adsorbed CB[7]s, and intracellular delivery of the dye to HCT116 cells was observed by confocal laser scanning microscopy. The dye-loaded particles (CB[7]
A new type of nanolabels for magnetic immunoassays was designed using individual superparamagneti... more A new type of nanolabels for magnetic immunoassays was designed using individual superparamagnetic ␥-Fe 2 O 3 nanoparticles. This innovative candidate is confronted here with commonly used micrometric beads. The innovative MIAplex ® technology allows to characterize and to quantify both types of labels with a competitive limit of detection. In this paper, we demonstrate the feasibility of multiparametric immunotests with the MIAplex ® technology. The carboxylic functions at the outer particle surface act as a precursor group for the covalent coupling of biological recognition molecules, such as antibodies, nucleic acids.
Nanomedicine: Nanotechnology, Biology and Medicine, 2012
A superparamagnetic γFe 2 O 3 nanocarrier was developed, characterized by spectroscopic methods a... more A superparamagnetic γFe 2 O 3 nanocarrier was developed, characterized by spectroscopic methods and evaluated for the delivery of a decoy oligonucleotide (dODN) in human colon carcinoma SW 480 cells. This nanoparticle-dODN bioconjugate (γFe 2 O 3 @dODN) was designed to target the signal transducer and activator of transcription 3, STAT3, a key regulator of cell survival and proliferation. We exploited a simple precipitation-redispersion mechanism for the direct and one-step complexation of a labeled decoy oligonucleotide with iron oxide nanoparticles (NPs). The cell internalization of the decoy γFe 2 O 3 @dODN nanoparticles is demonstrated and suggests the potential for DNA delivery in biological applications. Despite the increasing use of NPs in biology and medicine, convenient methods to quantify them within cells are still lacking. In this work, taking advantage of the nonlinear magnetic behavior of our superparamagnetic NPs, we have developed a new method to quantify in situ their internalization by cells.
Magnetic iron oxide nanoparticles differing in their size, shape (spherical, hexagonal, rods, cub... more Magnetic iron oxide nanoparticles differing in their size, shape (spherical, hexagonal, rods, cubes) and composition have been synthesized and modified using caffeic acid for transfer to aqueous media and stabilization of the particle suspensions at physiological pH. A super quantum interference device and the recently patented magnetic sensor MIAplex Ò , which registered a signal proportional to the second derivative of the magnetization curve, were used to study the magnetization behavior of the nanoparticles. The differences in the magnetic signatures of the nanoparticles (spheres and rods) make them promising candidates for the simultaneous detection of different types of biological molecules.
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