Doped-Iron Oxide Nanocrystals Synthesized by One-Step Aqueous Route for Multi-Imaging Purposes

Abstract

New doped inorganic nanocrystals (NC) consisting on iron oxide and other metal integrated into the structure have been synthesized in one-step by adapting the oxidant precipitation synthesis route for magnetite. Different metals have been chosen to confer extra and unique properties to the resulting magnetic heteronanostructure: Co and Gd for enhancing transversal and longitudinal relaxivities for Magnetic Resonance Imaging (MRI), and Bi and Au for achieving X-Ray absorption for CT imaging. Apart of that, gold optical properties are interesting for photothermal therapy and iron oxides for magnetic hyperthermia. All metals have been incorporated during the synthesis to the magnetite structure in different ways: by forming a solid solution, by modifying the surface of the NCs or by cocrystallization with the magnetite. The nanostructure formed in each case depends on the ionic radius of the secondary metal ion and the solubility of its hydroxide that control the co-precipitation in the initial steps of the reaction.Magnetic properties and imaging capabilities of the heteronanostructures have been analyzed as a function of the element distribution. Due to the synergistic combination of the different element properties, these magnetic heteronanostructures have great potential for biomedical applications.

Tunable magnetothermal properties of cobalt-doped magnetite–carboxymethylcellulose ferrofluids: smart nanoplatforms for potential magnetic hyperthermia applications in cancer therapy

“…19,45 Fig A/m.s) is lower than the recommended limit dose of 5 ×10 9 A/m•s, considering the safety of the patient under therapy avoiding uncontrolled heating of tissue caused by the induction of eddy currents and peripheral muscles stimulation. 13,14 As expected, the increase in the concentration of magnetic nanoparticles evidenced the enhancement of the ferrofluid temperature likely due to the magnetic dipolar interactions, which became more pronounced as the mean inter-particle distance was reduced. 32 Subsequently, in Fig.…”

“…It is well stated in the literature the increase of SAR parameter upon Co-doping up to values of x = 0.6 %. 13,14 This result was presumed, considering that the replacement of Fe 2+ by Co 2+ increases the magnetocrystalline anisotropy of the system, which is an efficient strategy to improve hyperthermia properties of the magnetite nanoparticles. 12 The increase in SAR values followed the same trend observed for the coercive field at low temperature as both parameters are associated with magnetic anisotropy of the systems (Fig.…”

“…However, the observed changes in crystallite sizes were also followed by the variation in the diameter of nanoparticles resulting in monodomain nanostructures. [13][14][15][16][17][18] This trend was expected even considering potential residual stress in the nanomaterials caused by gradual partial substitution of Fe 2+ species in the octahedral B sites of magnetite that possess an ionic radius (0.77 Å) by Co 2+ species with a smaller ionic radius (0.74 Å) as the lattice parameters were quite similar for magnetite (8.3963 Å) and cobalt ferrite (8.3919 Å) 13 . It should be noted that, according to the literature, [17][18][19] several aspects (e.g., amorphous phases and nanoparticle size) can interfere in the resolution of XRD patterns and, therefore, on the precision of Scherrer´s equation for directly measuring the average crystalline size of nanoparticles.…”

“…9B, right-axis). 13,14 Since SAR describes the efficiency of heat conversion, it is an important parameter for cancer nanomedicine from which one can determine the dosages applied to a tumor to achieve a reliable inactivation of target cells. For (nano)materials with high SAR values, it is possible to reduce the relative dose applied to the patient to a minimum level.…”

“…12 More interestingly, this effect can even be reached in nanoparticles with very small size, a condition that has good implications for biological application (e.g., prolongated circulation time of nanoparticles in the blood), but on the other hand, not satisfactory for the heat generation. 13,14 In this regard, the thorough understanding of the variation in structure and magnetic properties of magnetite nanoparticles conjugated with polymer ligands as a function of progressive Co-doping is of great interest for scientific and technological perspectives, which has not been comprehensively explored yet.…”