An ultrasensitive lateral-flow assay is developed for rapid quantitative detection of small molecules on-site. The conceptual novelty, which transfers lateral-flow assays to the category of highly sensitive quantitative systems, is due to employment of a bifunctional ligand combined with volumetric registration of magnetic nanolabels. The ligand provides extremely high affinity for trapping the nanolabels and, simultaneously, efficiently competes with the analyzed molecules for the limited quantity of antigen-binding sites on the nanolabels. The developed assay has been demonstrated as the first express method for measuring in human serum of free thyroxine (fT4). The limit of detection is 20 fМ or 16 fg/ml at the assay time <30 min with the dynamic range of 3 orders. Besides, we present the results of first characterization of kinetic parameters of interaction between free thyroxine and monoclonal antibody, as well as of competitive relationship between fT4 and fT4-biotin. The proposed universal platform can be used for ultrasensitive detection of small molecules in human in vitro diagnostics, veterinary, biosafety and counter-terrorism, food quality control, environmental monitoring, etc., as well as for search of new, previously undetectable, diagnostic markers in medicine.

中文翻译：

---

基于高亲和性双功能配体和磁性纳米标记的快速侧向流法超灵敏定量检测小分子

开发了一种超灵敏的横向流动检测方法，用于现场快速定量检测小分子。将横向流动分析转移到高度敏感的定量系统类别的概念新颖性是由于采用了双功能配体与磁性纳米标记的体积配准相结合。配体为捕获纳米标记提供了极高的亲和力，同时，有效地与分析的分子竞争纳米标记上有限数量的抗原结合位点。开发的检测方法已被证明是第一种在人血清中测量游离甲状腺素 (fT4) 的快速方法。检测限为 20 fМ 或 16 fg/ml，分析时间 <30 分钟，动态范围为 3 个数量级。除了，我们展示了游离甲状腺素和单克隆抗体之间相互作用的动力学参数的首次表征结果，以及 fT4 和 fT4-生物素之间的竞争关系。拟议的通用平台可用于人体体外诊断、兽医、生物安全和反恐、食品质量控制、环境监测等领域的小分子超灵敏检测，以及寻找新的、以前无法检测的诊断标志物在医学上。