Vamvakidis K, Katsikini M, Sakellari D, Paloura E C, Kalogirou O, Dendrinou-Samara C
Department of Chemistry, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece.
Dalton Trans. 2014 Sep 7;43(33):12754-65. doi: 10.1039/c4dt00162a.
Manganese ferrite (MnFe2O4) nanoparticles of identical size (9 nm) and with different inversion degrees were synthesized under solvothermal conditions as a candidate theranostic system. In this facile approach, a long-chain amine, oleylamine, was utilized as a reducing and surface-functionalizing agent. The synthesized nanoparticles were shown to have a cubic-spinel structure as characterized by TEM and XRD patterns. Control over their inversion degree was achieved by a simple change of manganese precursor from Mn(acac)2 to Mn(acac)3. The variation in the inversion degree is ascribed to the partial oxidation of Mn(2+) to Mn(3+), as was evidenced by X-ray absorption near edge structure spectroscopy and extended X-ray absorption fine structure spectroscopy at both the Fe and Mn K-edges. The reduction of the inversion degree from 0.42 to 0.22 is close to the corresponding bulk value of 0.20 and led to elevated magnetization (65.7 emu g(-1)), in contrast to the Néel temperature, which was decreased owing to the weaker superexchange interactions between the tetrahedral and octahedral sites within the spinel structure. In order to evaluate the performance of these nanoprobes as a possible bifunctional targeting system, the (1)H NMR relaxation of the samples was tested together with their specific loss power under an alternating magnetic field as a function of concentration. The hydrophobic as prepared MnFe2O4 nanoparticles converted to hydrophilic nanoparticles with cetyltrimethylammonium bromide (CTAB). The MnFe2O4 nanoparticles, well-dispersed in aqueous media, were shown to have r2 relaxivity of up to 345.5 mM(-1) s(-1) and heat release of up to 286 W g(-1), demonstrating their potential use for bioapplications.
在溶剂热条件下合成了尺寸相同（9纳米）但反演度不同的锰铁氧体（MnFe₂O₄）纳米颗粒，作为一种潜在的诊疗系统。在这种简便方法中，长链胺油胺被用作还原剂和表面功能化剂。通过透射电子显微镜（TEM）和X射线衍射（XRD）图谱表征，合成的纳米颗粒呈现立方尖晶石结构。通过将锰前驱体从Mn(acac)₂简单地改变为Mn(acac)₃实现了对其反演度的控制。反演度的变化归因于Mn(2+)部分氧化为Mn(3+)，这在Fe和Mn K边的X射线吸收近边结构光谱和扩展X射线吸收精细结构光谱中得到了证实。反演度从0.42降至0.22接近相应的体相值0.20，并导致磁化强度升高（65.7 emu g⁻¹），而奈尔温度由于尖晶石结构中四面体和八面体位点之间较弱的超交换相互作用而降低。为了评估这些纳米探针作为可能的双功能靶向系统的性能，测试了样品的¹H NMR弛豫以及它们在交变磁场下作为浓度函数的比损耗功率。制备的疏水性MnFe₂O₄纳米颗粒用十六烷基三甲基溴化铵（CTAB）转化为亲水性纳米颗粒。分散在水性介质中的MnFe₂O₄纳米颗粒显示出高达345.5 mM⁻¹ s⁻¹的r₂弛豫率和高达286 W g⁻¹的热释放，证明了它们在生物应用中的潜在用途。
