Vanhecke Dimitri, Crippa Federica, Lattuada Marco, Balog Sandor, Rothen-Rutishauser Barbara, Petri-Fink Alke
Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, CH-1700 Fribourg, Switzerland.
Chemistry Department, University of Fribourg, Chemin du Musée 9, 1700 Fribourg, Switzerland.
Materials (Basel). 2020 Apr 25;13(9):2018. doi: 10.3390/ma13092018.
Magnetosomes are near-perfect intracellular magnetite nanocrystals found in magnetotactic bacteria. Their synthetic imitation, known as superparamagnetic iron oxide nanoparticles (SPIONs), have found applications in a variety of (nano)medicinal fields such as magnetic resonance imaging contrast agents, multimodal imaging and drug carriers. In order to perform these functions in medicine, shape and size control of the SPIONs is vital. We sampled SPIONs at ten-minutes intervals during the high-temperature thermal decomposition reaction. Their shape (sphericity and anisotropy) and geometric description (volume and surface area) were retrieved using three-dimensional imaging techniques, which allowed to reconstruct each particle in three dimensions, followed by stereological quantification methods. The results, supported by small angle X-ray scattering characterization, reveal that SPIONs initially have a spherical shape, then grow increasingly asymmetric and irregular. A high heterogeneity in volume at the initial stages makes place for lower particle volume dispersity at later stages. The SPIONs settled into a preferred orientation on the support used for transmission electron microscopy imaging, which hides the extent of their anisotropic nature in the axial dimension, there by biasing the interpretation of standard 2D micrographs. This information could be feedback into the design of the chemical processes and the characterization strategies to improve the current applications of SPIONs in nanomedicine.
磁小体是在趋磁细菌中发现的近乎完美的细胞内磁铁矿纳米晶体。它们的合成仿制品，即超顺磁性氧化铁纳米颗粒（SPIONs），已在多种（纳米）医学领域得到应用，如磁共振成像造影剂、多模态成像和药物载体。为了在医学中发挥这些功能，控制SPIONs的形状和大小至关重要。我们在高温热分解反应过程中每隔十分钟对SPIONs进行采样。使用三维成像技术获取它们的形状（球形度和各向异性）和几何描述（体积和表面积），该技术能够对每个颗粒进行三维重建，随后采用体视学定量方法。由小角X射线散射表征支持的结果表明，SPIONs最初呈球形，然后变得越来越不对称和不规则。初始阶段体积的高度异质性在后期被较低的颗粒体积分散性所取代。SPIONs在用于透射电子显微镜成像的支撑物上定向排列，这掩盖了它们在轴向维度上的各向异性程度，从而使对标准二维显微照片的解释产生偏差。这些信息可以反馈到化学过程设计和表征策略中，以改进SPIONs在纳米医学中的当前应用。
