Signal amplification in colorimetric biosensors usually requires labile reagents and/or additional steps, which are not ideal for in-field measurements. Here we show that the limit of detection of a gold nanoparticle-labeled colorimetric immunosensor can be decreased 10-fold by performing the assay on a folded piece of paper. In this approach, the intrinsic porosity of the substrate enables generating multiple signals with a single drop of reagent. This yields combined signals with higher optical density thanks to the semitransparent nature of the wet material. It will be shown that this method can decrease the limit of detection 10 times in a model immunosensor for the detection of immunoglobulins. The procedure is so straightforward that it could be easily implemented to decrease the limit of detection of microfluidic paper-based analytical devices with colorimetric readouts.

比色生物传感器中的信号放大通常需要不稳定的试剂和/或其他步骤，这对于现场测量而言并不理想。在这里，我们表明，通过在折叠的纸上进行测定，金纳米粒子标记的比色免疫传感器的检测极限可以降低10倍。在这种方法中，基体的固有孔隙率使得只需一滴试剂即可产生多个信号。由于湿材料的半透明特性，因此可以产生具有更高光密度的组合信号。将显示，该方法可以在用于检测免疫球蛋白的模型免疫传感器中将检测极限降低10倍。