Aptamer-based origami paper analytical device for electrochemical detection of adenosine.
Aptamer-based origami paper analytical device for electrochemical detection of adenosine.
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DOI：
10.1002/anie.201202929
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发表时间：
2012-07-09
影响因子：
16.6
通讯作者：
Crooks, Richard M
中科院分区：
文献类型：
--
作者：
Liu, Hong;Xiang, Yu;Lu, Yi;Crooks, Richard M
自供电折纸分析装置（oPAD）使用适体来识别分析物，使用葡萄糖氧化酶（GOx）标签来修改电活性氧化还原对的相对浓度，以及使用数字万用表（DMM）来验证测定结果。传感器是自供电的，因为它自产生电信号，因此读出过程类似于测试电池。传感器的原理如图1所示。简而言之，该设备被打印在一张纸上，折叠成三维（3D）配置，然后层压在塑料中。在入口处加载样品的等分试样，将其分成两个通道，然后引导至通道内截留的微珠。在一个通道中，固定在微珠上的适体与靶标结合，并释放出GOx标记的DNA链，该DNA链流向下游。另一通道中的微珠上不存在适体，其用作对照。分离的流体终止于沙漏形的双室电化学电池中。沙漏的腰部充当两个半电池之间的盐桥。在其中一个半电池中，GOx催化葡萄糖的氧化，这进而导致[Fe（CN）6] 3 β转化为[Fe（CN）6] 4 β。感测半电池和控制半电池中的[Fe（CN）6] 3H2和[Fe（CN）6] 4H2的浓度差异导致用于对电容器充电的电压。当开关（示意图1的下部）闭合时，电容器通过DMM放电。电容器提供高瞬时电流，实际上是放大的电流，因此比直流测量灵敏度更高。该设备及其操作功能很重要，原因有五个。首先，将适体固定在捕获在纸流体通道内的微珠上。与直接固定在纸上相比，这种设计大大简化了探针的引入[1]，因为现有的珠固定和表征方法可用于一系列不同的探针家族，包括适体，DNA酶[2，3]和抗体。第二，如在该装置中配置的，珠固定消除了对洗涤步骤的需要。第三，尽管适体和其他核酸探针已被用于测试条上，[4]但它们尚未与使用图案化纸的流体装置整合。适体可以结合到广泛的目标，包括那些（如腺苷目标，我们报告），是没有免疫原性。[2]此外，核酸探针通常比基于蛋白质的探针更稳定。[5]第四，传感器是基于一个浓度单元，它的作用就像一个电池充电的电容器，随后读出使用数字万用表。后者具有非常宽的动态范围，并且电容器的使用导致定量响应，与直流测量相比，灵敏度提高了17倍。最后，使用脉冲边缘热层压将器件封装在塑料中，这解决了许多问题，包括流体蒸发、试剂失活和器件污染。纸流控技术起源于侧流测试条，该测试条于1988年由Unipath以家用妊娠测试试剂盒的形式首次商业化发布。[6]该系列设备的低成本和易用性确保了可用测定类型数量的扩展，特别是对于即时护理应用。[5]2007年，Whitesides和同事通过开发一种将纸基材分为亲水性和疏水性区域的方法，为基本的侧向流设计增加了功能。[7]这些类型的装置现在被称为微流体纸分析装置（μ PAD）。[8-13 ...
A self-powered origami paper analytical device (oPAD) uses an aptamer to recognize an analyte, a glucose oxidase (GOx) tag to modify the relative concentrations of an electroactive redox couple, and a digital multimeter (DMM) to transduce the result of the assay. The sensor is self-powered in that it self-generates an electrical signal so that the read-out process is similar to testing a battery. The principle of the sensor is illustrated in Scheme1. Briefly, the device is printed on a single piece of paper, folded into a three-dimensional (3D) configuration, and then laminated in plastic. An aliquot of sample is loaded at the inlet, split into two channels, and then directed to microbeads entrapped within the channels. In one channel, an aptamer immobilized on microbeads binds to the target and releases a GOx-labeled DNA strand that flows downstream. No aptamer is present on the microbeads in the other channel, which is used as a control. The split fluids terminate in an hour-glass-shaped, two-compartment electrochemical cell. The waist of the hour glass serves as a salt bridge between the two half-cells. In one of the half-cells, GOx catalyzes the oxidation of glucose, which in turn results in conversion of [Fe (CN) 6] 3À to [Fe (CN) 6] 4À. The difference in concentrations of [Fe (CN) 6] 3À and [Fe (CN) 6] 4À in the sensing half-cell and control half-cell results in a voltage that is used to charge a capacitor. When the switch (lower part of Scheme1) is closed, the capacitor discharges through the DMM. The capacitor provides a high instantaneous current, in effect an amplified current, and hence a higher sensitivity than a direct current measurement. This device and its operational features are important for five reasons. First, the aptamer is immobilized on microbeads trapped within the paper fluidic channel. This design greatly simplifies probe introduction, compared to direct immobilization on paper,[1] because existing bead immobilization and characterization methods can be used for a range of different probe families, including aptamers, DNAzymes,[2, 3] and antibodies. Second, as configured in this device, bead immobilization eliminates the need for a washing step. Third, although aptamers and other nucleic acid probes have been used on test strips,[4] they have not been integrated with fluidic devices using patterned paper. Aptamers can bind to a wide range of targets, including those (like the adenosine target we report) that are not immunogenic.[2] Moreover, nucleic acid probes are generally more stable than those based on proteins.[5] Fourth, the transducer is based on a concentration cell, which acts like a battery to charge a capacitor that is subsequently read-out using a DMM. The latter has a very wide dynamic range, and the use of the capacitor results in a quantitative response that yields a 17-fold enhancement of sensitivity compared to a direct current measurement. Finally, the device is encapsulated in plastic using impulse edge thermal lamination, which solves many problems, including fluid evaporation, reagent deactivation, and device contamination. Paper fluidics have their genesis in the lateral flow test strip, which was first released commercially by Unipath in 1988 in the form of a home pregnancy test kit.[6] The low cost and ease of use of this family of devices ensured an expansion in the number of types of assays available, particularly for point-of-care applications.[5] In 2007, Whitesides and coworkers added functionality to the basic lateral flow design by developing a means for dividing the paper substrate into hydrophilic and hydrophobic regions.[7] These types of devices are now known as microfluidic paper analytical devices (μPADs).[8–13 …