Abstract
Superparamagnetic iron oxide nanoparticles (SPIONs) have shown great potential in biomedicine due to their high intrinsic magnetization behaviour. These are small particles of magnetite or maghemite, and when coated, their surface oxidation is prevented, their aggregation tendency is reduced, their dispersity is improved, and the stability and blood circulation time are increased, which are mandatory requirements in biomedical applications. In this work, SPIONs were synthesized in air through a reduction-precipitation method and coated with four different polymers (Polyethylene glycol(PEG) 1000/6000 and dextran T10/T70). All the synthesized samples were structurally and magnetically characterized by transmission electron microscopy, Fourier transform infra-red spectroscopy, X-ray powder diffraction, Mössbauer spectroscopy, and Superconducting Quantum Interference Device (SQUID) magnetometry. SPIONs centrifuged and dried in vacuum with an average diameter of at least 7.5 nm and a composition ≤60% of maghemite and ≥40% of magnetite showed the best magnetization results, namely a saturation magnetization of ~64 emu/g at 300 K, similar to the best reported values for SPIONs prepared in controlled atmosphere. As far as SPIONs’ coatings are concerned, during their preparation procedure, surface polymers must be introduced after the SPIONs’ precipitation. Furthermore, polymers with shorter chains do not affect the SPIONs’ magnetization performance, although longer chain polymers significantly decrease the coated particle magnetization values, which is undesirable.
Highlights
Superparamagnetic iron oxide nanoparticles (SPIONs), the only clinically approved metal oxide nanoparticles (NPs) [1], emerge as medically interesting nanoparticles (NPs), being able to integrate multifunctional platforms and to perform multiple objectives such as imaging and therapy, or to perform a single advanced function through the incorporation of multiple functional units [2,3,4,5,6,7,8,9]
Hydrophobic surface NPs are, in general, rapidly and efficiently coated with plasma components being rapidly removed from the mammal’s circulation system, while some hydrophilic NPs are able to resist this immune system elimination process, for example, those which are coated with polymers such as polyethylene glycol (PEG) or dextran [27,28,29]
SPIONs were synthesized as described in the previous Section 2.2.1 and their coating was made as follows: 800 mg of SPIONs were suspended in 10 mL of 0.5 M NaOH and 4% w/w of polymer (PEG 1000/6000 or dextran T10/T70) was dissolved in 10 mL of 0.5 M NaOH
Summary
Superparamagnetic iron oxide nanoparticles (SPIONs), the only clinically approved metal oxide nanoparticles (NPs) [1], emerge as medically interesting nanoparticles (NPs), being able to integrate multifunctional platforms and to perform multiple objectives such as imaging and therapy, (theranostics) or to perform a single advanced function through the incorporation of multiple functional units [2,3,4,5,6,7,8,9]. The composition of protein corona is strongly dependent on the physicochemical properties of NPs. Hydrophobic surface NPs are, in general, rapidly and efficiently coated with plasma components (corona/opsonins) being rapidly removed from the mammal’s circulation system (by phagocytose and clearance), while some hydrophilic NPs are able to resist this immune system elimination process, for example, those which are coated with polymers such as polyethylene glycol (PEG) or dextran [27,28,29]. It is important to mention that this surface coating, depending on its nature, amount, composition and thickness, may affect the inherent magnetic properties of SPIONs. SPIONs’ size is another final parameter in the capability to reach and interact with target cells [32,33]. Two different magnetic behaviours have been identified as dependent on SPIONs’ dimensions
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