Effect of chain length and electrical charge on properties of ammonium-bearing bisphosphonate-coated superparamagnetic iron oxide nanoparticles: formulation and physicochemical studies
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Bisphosphonates BP molecules have shown to be efficient for coating superparamagnetic iron oxide particles. In order to clarify the respective roles of electrical charge and the length of the molecules, bisphosphonates with one or two ammonium moieties with an intermediate aliphatic group of 3, 5 or 7 carbons were synthesized and iron oxide nanoparticles coated. The evaluation on their iron core properties was made by transmission electron microscopy (TEM), nuclear magnetic relaxation dispersion (NMRD) profiles and Mössbauer spectra. The core size is close to 5 nm, with a global superparamagnetic behaviour modified by a paramagnetic Fe-based layer, probably due to surface crystal alteration. The hydrodynamic sizes increase slightly with aliphatic chain length (from 9.8 to 18.6 nm). The presence of one or two ammonium group(s) lowers the negative electrophoretic mobility up to bear zero values but reduces their colloidal stability. These BP-coated iron oxide nanoparticles are promising Magnetic Resonance Imaging (MRI) contrast agents.
KeywordsIron oxides Contrast agents Superparamagnetic behaviour Bisphosphonates NMRD profiles Mössbauer spectrometry Colloids Magnetic Resonance Imaging
Financial support provided by ‘Collectivités territoriales’ of Angers is gratefully acknowledged. The work of NMRD profiles was supported by the FNRS and the ARC Program 05/10-335 of the French Community of Belgium. The support and sponsorship concerted by COST Action D38 and the EMIL project are kindly acknowledged.
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