Department of Physical and Analytical Chemistry & Institute of Biotechnology of Asturias, University of Oviedo, c/Julián Clavería 8, 33006 Oviedo, Spain.
Department of Physics & IUTA, University of Oviedo, Campus de Viesques, 33204 Gijón, Spain.
Biosensors (Basel). 2020 Jul 22;10(8):80. doi: 10.3390/bios10080080.
Superparamagnetic iron oxide nanoflowers coated by a black carbon layer (FeO@C) were studied as labels in lateral flow immunoassays. They were synthesized by a one-pot solvothermal route, and they were characterized (size, morphology, chemical composition, and magnetic properties). They consist of several superparamagnetic cores embedded in a carbon coating holding carboxylic groups adequate for bioconjugation. Their multi-core structure is especially efficient for magnetic separation while keeping suitable magnetic properties and appropriate size for immunoassay reporters. Their functionality was tested with a model system based on the biotin-neutravidin interaction. For this, the nanoparticles were conjugated to neutravidin using the carbodiimide chemistry, and the lateral flow immunoassay was carried out with a biotin test line. Quantification was achieved with both an inductive magnetic sensor and a reflectance reader. In order to further investigate the quantifying capacity of the FeO@C nanoflowers, the magnetic lateral flow immunoassay was tested as a detection system for extracellular vesicles (EVs), a novel source of biomarkers with interest for liquid biopsy. A clear correlation between the extracellular vesicle concentration and the signal proved the potential of the nanoflowers as quantifying labels. The limit of detection in a rapid test for EVs was lower than the values reported before for other magnetic nanoparticle labels in the working range 0-3 × 10 EVs/μL. The method showed a reproducibility (RSD) of 3% (n = 3). The lateral flow immunoassay (LFIA) rapid test developed in this work yielded to satisfactory results for EVs quantification by using a precipitation kit and also directly in plasma samples. Besides, these FeO@C nanoparticles are easy to concentrate by means of a magnet, and this feature makes them promising candidates to further reduce the limit of detection.
用碳层（FeO@C）包裹的超顺磁氧化铁纳米花被用作侧向流动免疫分析中的标记物。它们通过一锅溶剂热法合成，并进行了（尺寸、形态、化学成分和磁性能）表征。它们由几个嵌入在保持羧基的碳涂层中的超顺磁核组成，这些羧基适合生物偶联。它们的多核结构对于磁性分离特别有效，同时保持了适合免疫分析报告物的磁性和适当的尺寸。它们的功能通过基于生物素-亲和素相互作用的模型系统进行了测试。为此，使用碳二亚胺化学将纳米粒子与亲和素偶联，并使用生物素测试线进行侧向流动免疫分析。使用感应磁传感器和反射阅读器进行了定量。为了进一步研究 FeO@C 纳米花的定量能力，将磁性侧向流动免疫分析作为一种检测系统进行了测试，用于检测细胞外囊泡（EVs），这是一种具有液体活检应用前景的新型生物标志物来源。EV 浓度与信号之间的明显相关性证明了纳米花作为定量标记物的潜力。用于 EV 的快速检测的检测限低于以前报道的其他磁性纳米粒子标记物在 0-3×10 EV/μL 工作范围内的检测限。该方法的重现性（RSD）为 3%（n=3）。使用沉淀试剂盒和直接在血浆样品中，本工作开发的侧向流动免疫分析（LFIA）快速测试对 EVs 的定量取得了令人满意的结果。此外，这些 FeO@C 纳米粒子易于通过磁铁进行浓缩，这一特性使它们有望进一步降低检测限。
