Epoxy Ring Opening Phase Transfer as a General Route to Water Dispersible Superparamagnetic Fe₃O₄ Nanoparticles and Their Application as Positive MRI Contrast Agents

Abstract

A novel and effi cient method to produce water dispersible superparamagnetic Fe 3 O 4 nanoparticles is described. Nanoparticles prepared by non-hydrolytic organic phase methods are subsequently functionalized with (3-glycidyloxypropyl)trimethoxysilane, a linker that prevents aggregation and is available for subsequent coupling reactions with a wide range of polymers and biomolecules. Ring opening coupling reactions were used to coat the epoxy-functionalized magnetite nanoparticles with aminated polymers (polyetheramines) or small molecules (arginine). The resulting nanoparticles, with hydrodynamic size of 13 nm, are found to be very stable over extended periods in water or PBS due to the presence of a dense stabilizer layer covalently anchored to the surface. Exceptionally high spin-lattice relaxivity, r 1 , values of 17 s − 1 mM − 1 , and low r 2 / r 1 ratios of 3.3-3.8 were exhibited in the clinical MRI frequency range, irrespective of the molecule selected for nanoparticle stabilization. As a result the dispersions are excellent candidates for incorporation into multifunctional assemblies or for use as positive contrast agent for MRI.

Size‐Controlled Nanoparticle Clusters of Narrow Size‐Polydispersity Formed Using Multiple Particle Types Through Competitive Stabilizer Desorption to a Liquid–Liquid Interface

“…Monodisperse primary FeO NP dispersions in CHCl 3 , of hydrodynamic size ( d hyd ) c . 15 nm, were prepared using previously reported methods, which are derived from the surfactant‐free thermal decomposition process described by Pinna et al Following synthesis in benzyl alcohol (BA) the NPs were stabilized using a controlled quantity of oleic acid (OA) surfactant molecules, corresponding to 0.75 monolayer equivalents in the final suspension (assuming a binding footprint of 3.8 × 10 −19 m 2 , and 100% monodisperse spherical NPs). It was found that the assembly experiment is very sensitive to the quantity of stabilizer used in forming the NP dispersion.…”

Controlling the magnetic properties of polymer–iron oxide nanoparticle composite thin films via spatial particle orientation

“…Magnetic nanoparticles are of interest due to their potential for use in a wide range of important technological applications such as magnetic recording media, 1-4 magnetoelectronic devices, 5-7 ferrouids, 8,9 nanomedicine, [10][11][12][13][14][15][16] and so magnetic materials for magnetic sensors. [17][18][19] Magnetic nanoparticle composites in a nonmagnetic polymer matrix have also become important due to the continued demand associated with the development of biomedical applications, [10][11][12][13]16,20,21 high-density storage materials., [1][2][3]22 and mechanical reinforcement.…”

Design of a fluorinated magneto-responsive material with tuneable ultrasound scattering properties

“…If perfluorooctanoic acid (PFOA) was shown to exhibit very slow 35 clearance from living organisms, 3,4 as ascribed to the outstanding stability of carbon-fluorine bonds, other fluorinated chemicals are considered as "bio-safe". Among them, fluorinated ultrasound contrast agents (UCA) commonly referred to as "microbubbles" are authorized for intravenous injection in humans under brand 40 names as SonoVue  , Optison  , Imavis  , Definity  , Imagent  ... Due to their very low solubility in water (less than 10 ppm) and, on the contrary, to their high compressibility and ability to dissolve large quantities of gases (O 2 , N 2 , CO 2 ...), 5 volatile fluorocarbons can indeed be used to fill the inner components of 45 microbubbles. The UCA echogenicity relies on the impedance contrast between tissues mainly made of water (Z water ≈ 1.5×10 6 Rayl) and the materials to be injected, which is often a gas phase (Z air ≈ 340 Rayl).…”

“…26, 28-30 Apart from APTS, other organosilanes were grafted onto the surface of iron oxide MNPs, such as (3-glycidyloxypropyl)trimethoxysilane, 31 40 cyanoethyltrimethoxysilane, 32 or 2-bromo-2-methyl-N-(3-(triethoxysilyl)propyl) propanamide to initiate polymer chain growth by a "grafting-from" controlled polymerisation method. 33 In almost all the previous works, silanization was an intermediate step needed to anchor a molecular shell around the magnetic 45 cores by covalent bonds, which is preferable than most common adsorption routes with chelating ligands such as carboxylic acids, phosphates, sulfonates or catechols. Only macromolecular silanes such as triethoxy(methoxypolyethyleneoxy)silane 29 or trifluoroethylester-poly(ethyleneglycol) 30 were shown to achieve 50 direct colloidal stabilisation of MNPs in water before any further coupling reaction.…”