Integration of a screening-guided near-infrared aptasensor into a portable platform for quantitative on-site...

N¹-Methyladenosine (m¹A) is an important RNA modification associated with diverse biological processes and disease states, yet rapid and quantitative on-site detection of m¹A remains challenging. Herein, we report a near-infrared aptasensor (NiRApt) for the quantitative detection of m¹A based on a screening-guided strategy to identify an optimal dye-aptamer pair. Systematic evaluation of 32 commercially available fluorescent dyes identified crystal violet (CV) as an optimal NIR reporter for an m¹A aptamer. Aptamer binding enhances CV fluorescence, while competitive binding of m¹A induces efficient dye displacement and fluorescence quenching. The NiRApt exhibits a linear response to m¹A from 0 to 2 µM with a detection limit of 0.09 µM and high selectivity against structurally related nucleosides. Direct analysis of m¹A in human urine was achieved without pretreatment. Integration with a portable fluorometer enables quantitative on-site detection without reliance on smartphone-based imaging, providing a general and practical framework for portable aptamer-based sensing.