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” molecular 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.