Naked-eye quantitative aptamer-based assay on paper device

This work initially describes the design of low-cost, naked-eye quantitative aptamer-based assays by using microfluidic paper-based analytical device (μPAD). Two new detection motifs are proposed for quantitative μPAD measurement without using external electronic readers, which depend on the length of colored region in a strip-like μPAD and the number of colorless detection microzones in a multi-zone μPAD. The length measuring method is based on selective color change of paper from colorless to blue–black via formation of iodine–starch complex. The counting method is conducted on the basis of oxidation–reduction reaction between hydrogen peroxide and potassium permanganate. Their utility is well demonstrated with sensitive, specific detection of adenosine as a model analyte with the naked eye in buffer samples and undiluted human serum. These equipment-free quantitative methods proposed thus hold great potential for the development of more aptamer-based assays that are simple, cost-efficient, portable, and user-friendly for various point-of-care applications particularly in resource-constrained environments. •Naked-eye quantitative aptamer-based assays on paper devices are firstly reported.•Two new methods are used for equipment-free quantitative readout of paper devices.•Sensitive detection of adenosine in human serum with the naked eye is achieved.