Lactoferrin is an abundant glycoprotein in human body fluids and is known as a biomarker for various diseases. Therefore, point-of-care testing (POCT) for lactoferrin is of interest. Microfluidic paper-based analytical devices (µPADs) have gained a lot of attention as next-generation POCT device candidates, due to their inexpensiveness, operational simplicity, and being safely disposable. This work presents a colorimetric sensing approach for quantitative lactoferrin analysis. The detection mechanism takes advantage of the high affinity of lactoferrin to ferric ions (Fe3+). Lactoferrin is able to displace an indicator from a colorimetric 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP)-Fe3+ complex, resulting in a color change. A 5-Br-PADAP-Fe3+ complex was encapsulated into water-dispersible poly(styrene-block-vinylpyrrolidone) particles, whose physical entrapment in the cellulosic fiber network results in the immobilization of the complex to the paper matrix. The complex-encapsulating particles showed a color change response in accordance with lactoferrin concentration. Both color intensity-based paper well plates and distance readout-based µPADs are demonstrated. Color intensity-based devices allowed quantitative analysis of lactoferrin concentrations with a limit of detection of 110 µg/mL, using a smartphone and a color readout app. On the other hand, distance readout-based µPADs showed changes of the length of colored sections in accordance with lactoferrin concentration. In summary, we successfully developed both colorimetric intensity-based paper wells and distance-based µPADs for lactoferrin detection. This work demonstrates a user-friendly colorimetric analysis platform for lactoferrin without requiring lab equipment and expensive antibodies.

中文翻译：

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比色法检测乳铁蛋白的微流控纸基分析设备。

乳铁蛋白是人体体液中丰富的糖蛋白，被称为各种疾病的生物标志物。因此，乳铁蛋白的即时检测（POCT）引起了人们的兴趣。基于微流体纸质的分析设备（µPAD）由于其价格便宜，操作简便且可安全使用，因此成为下一代POCT设备的候选者。这项工作提出了用于定量乳铁蛋白分析的比色传感方法。检测机制利用了乳铁蛋白对三价铁离子（Fe3 +）的高亲和力。乳铁蛋白能够从比色的2-（5-溴-2-吡啶基偶氮）-5-二乙基氨基苯酚（5-Br-PADAP）-Fe3 +复合物中取代指示剂，从而导致颜色变化。将5-Br-PADAP-Fe3 +复合物封装在水分散性聚（苯乙烯嵌段-乙烯基吡咯烷酮）颗粒中，该颗粒在纤维素纤维网络中的物理截留导致复合物固定在纸基上。配合物包封的颗粒根据乳铁蛋白浓度显示出颜色变化响应。演示了基于颜色强度的纸质孔板和基于距离读数的µPAD。基于颜色强度的设备可以使用智能手机和颜色读取应用程序对乳铁蛋白浓度进行定量分析，检测限为110 µg / mL。另一方面，基于距离读数的µPAD显示出有色部分的长度根据乳铁蛋白浓度而变化。综上所述，我们成功开发了基于比色强度的纸孔和基于距离的µPAD，用于乳铁蛋白检测。这项工作证明了无需乳化设备和昂贵抗体即可对乳铁蛋白进行用户友好的比色分析平台。