Identifying the precise location of cells and their migration dynamics is of utmost importance for achieving the therapeutic potential of cells after implantation into a host. Magnetic resonance imaging is a suitable, non-invasive technique for cell monitoring when used in combination with contrast agents. This work shows that nanowires with an iron core and an iron oxide shell are excellent materials for this application, due to their customizable magnetic properties and biocompatibility. The longitudinal and transverse magnetic relaxivities of the core–shell nanowires were evaluated at 1.5 T, revealing a high performance as T2 contrast agents. Different levels of oxidation and various surface coatings were tested at 7 T. Their effects on the T2 contrast were reflected in the tailored transverse relaxivities. Finally, the detection of nanowire-labeled breast cancer cells was demonstrated in T2-weighted images of cells implanted in both, in vitro in tissue-mimicking phantoms and in vivo in mouse brain. Labeling the cells with a nanowire concentration of 0.8 μg of Fe/mL allowed the detection of 25 cells/µL in vitro, diminishing the possibility of side effects. This performance enabled an efficient labelling for high-resolution cell detection after in vivo implantation (~ 10 nanowire-labeled cells) over a minimum of 40 days. Iron-iron oxide core–shell nanowires enabled the efficient and longitudinal cellular detection through magnetic resonance imaging acting as T2 contrast agents. Combined with the possibility of magnetic guidance as well as triggering of cellular responses, for instance by the recently discovered strong photothermal response, opens the door to new horizons in cell therapy and make iron-iron oxide core–shell nanowires a promising theranostic platform.

中文翻译：

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磁性核壳纳米线作为细胞追踪的 MRI 造影剂


识别细胞的精确位置及其迁移动态对于实现细胞植入宿主后的治疗潜力至关重要。当与造影剂结合使用时，磁共振成像是一种合适的、非侵入性的细胞监测技术。这项工作表明，具有铁芯和氧化铁壳的纳米线由于其可定制的磁性和生物相容性而成为该应用的优异材料。在 1.5 T 下评估了核壳纳米线的纵向和横向磁弛豫率，显示出作为 T2 造影剂的高性能。在 7 T 下测试了不同水平的氧化和各种表面涂层。它们对 T2 对比度的影响反映在定制的横向弛豫率中。最后，在体外模拟组织模型和体内小鼠大脑中植入的细胞的 T2 加权图像中证明了纳米线标记的乳腺癌细胞的检测。用浓度为 0.8 μg Fe/mL 的纳米线标记细胞，可以在体外检测到 25 个细胞/μL，从而减少了副作用的可能性。这种性能能够在体内植入后（约 10 个纳米线标记的细胞）在至少 40 天内进行有效标记，以进行高分辨率细胞检测。铁-氧化铁核壳纳米线作为 T2 造影剂，通过磁共振成像实现高效、纵向的细胞检测。结合磁引导的可能性以及触发细胞反应的可能性，例如最近发现的强光热反应，为细胞治疗的新视野打开了大门，并使铁-氧化铁核壳纳米线成为一个有前途的治疗诊断平台。