Ultrasensitive colorimetric and fluorescent dual-readout assay for D-penicillamine based on the chloride boosted oxidative ability of copper ions

Dual-readout protocols with two signal transduction channels can significantly improve the detection precision and diversity. In contrast to the previous tedious and time-consuming preparation of two response materials, a convenient and commercially available small molecule o-Phenylenediamine (OPD)-based dual-mode system was developed for the ultrasensitive detection of D-penicillamine (D-PA). Fortunately and interestingly, it is demonstrated that chloride ions (Cl-) could largely enhance the oxidative ability of copper ions (Cu2+) and improve the reaction rate and efficiency of the Cu2+-OPD system, leading to the boosted colorimetric and fluorescent signals and shorter reaction time. Meanwhile, D-PA could strongly bind with Cu2+ to form a stable Cu2+-D-PA complex, thereby inhibiting the aforementioned oxidation process and exhibiting decrease of absorbance values and fluorescence intensity. Inspired by the excellent analytical performance, an "INH" mo-lecular logic gate was devised by employing Cl- and D-PA as the inputs, and the dual-mode strategy has been successfully employed to probe D-PA in tablets and human serum samples. Such cost-effective yet efficacious analytical tool not only improve the sensing performance of the Cu2+-OPD reaction system, but also enhance the detection sensitivity for D-PA and promote the application and development of OPD-based reactions.