Efficient removal of interferents from complex matrices would significantly improve the performance of state of the art dipstick assays. Herein, we evaluate a graphitized carbon black (GCB)-incorporated dipstick, a configuration that has not been explored before, for reliable and facile on-site analysis of complex matrices. Carrot juice, a highly pigmented sample matrix, is chosen for evaluating the retention of interferents within the sorbent-incorporated cleanup pad on the dipstick. A peptide with a specific cleavage site for botulinum neurotoxin A light chain (BoNT/A LC), a model protease for validation of the proposed dipstick assay, is incubated with the test samples containing BoNT/A LC. Subsequently, the BoNT/A LC digested substrate and sample matrix flow vertically through the GCB-deposited cleanup pad within which the matrix interferents are captured, while the substrate, with a minimum of interferents, continues to flow toward a conjugation pad for labelling with Europium particles. Finally, the cleaved and uncleaved substrates flow toward a detection zone, where they bind to the test line producing a pinkish band which is not visible in the absence of GCB incorporation. The dipstick assay yields a LOD of 0.1 nM (5 ng/mL) of BoNT/A LC in carrot juice, within 20 min. The reported approach enables detection of proteases in a wide range of matrices upon incorporation of appropriate sorbents, ultimately aiming to exclude tedious laboratory-based sample pre-treatment protocols. Thus, merging extraction, cleanup, and pre-concentration steps with a sensitive optical detection approach is an attractive strategy for on-site assaying in complex matrices. Graphical abstract.

中文翻译：

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掺有吸附剂的量油尺可直接测定蛋白酶。

从复杂基质中有效去除干扰物将显着改善现有量油尺检测的性能。在本文中，我们评估了一种石墨化炭黑（GCB）掺入量油尺，该量尺以前未曾探索过，可用于复杂基质的可靠且便捷的现场分析。选择胡萝卜汁（一种色素含量高的样品基质）来评估干扰物在量油尺上结合有吸附剂的清洁垫内的保留。将具有肉毒杆菌神经毒素A轻链（BoNT / A LC）特异性切割位点的肽（一种用于验证所建议的试纸法的模型蛋白酶）与含有BoNT / A LC的测试样品一起孵育。后来，BoNT / A LC消化的底物和样品基质垂直流过GCB沉积的净化垫，其中捕获了基质干扰物，而底物中的干扰物最少，继续流向结合垫，用with颗粒进行标记。最后，裂解和未裂解的底物流向检测区，在此处它们结合到测试线，产生带粉红色的条带，在没有引入GCB的情况下看不到该条带。量油尺检测在20分钟内在胡萝卜汁中产生的BoNT / A LC的LOD为0.1 nM（5 ng / mL）。所报道的方法能够在掺入适当的吸附剂后检测多种基质中的蛋白酶，最终目的是排除基于实验室的乏味样品预处理方案。因此，合并提取，清理，灵敏的光学检测方法进行预浓缩步骤是在复杂基质中进行现场分析的一种有吸引力的策略。图形概要。