Colorimetric and fluorometric detection of NADPH using imidazolium functionalized polydiacetylenes with high sensitivity and selectivity

The nicotinamide adenine dinucleotide derivatives (NADPH, NADP⁺, NADH, and NAD⁺) are important redox cofactors that involve in many biological activities, and their concentration levels are associated with a variety of diseases. In this work, an imidazolium functionalized polydiacetylenes sensing system (IM-PDAs) is reported to selectively detect the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH). Depending on the electrostatic attraction between the positively charged imidazolium heads and the negatively charged phosphate groups, the sensing system exhibits colorimetric and fluorescent responses when exposed to NADPH and its oxidized form (NADP⁺); while the system does not respond to the less negatively charged NADH and NAD⁺ at the concentration range tested in this study. Owing to the positively charged nicotinamide of NADP⁺, the detection sensitivity of IM-PDAs towards NADP⁺ is much lower than that towards NADPH, successfully differentiating NADPH from the rest three cofactors. Furthermore, IM-PDAs loaded paper-based sensor is constructed and demonstrates the potentials of IM-PDAs based sensing device for practical applications in NADPH detection.