A colorimetric indicator-displacement assay for cysteine sensing based on a molecule-exchange mechanism

In this study, we developed an ingenious yet effective strategy for cysteine detection. The calorimetric cysteine assay is established through an indicator displacement process, where Cu2+ and pyrocatechol violet (PV) was employed as receptor and indicator, respectively. Proof-of-concept trials demonstrated that the stronger binding affinity of Cu2+ receptor toward cysteine than PV indicator endowed our calorimetric sensor with high selectivity and excellent sensitivity as well as with a lower detection limit (4.60 mu M and 120 mu M, S/N =3) by UV visible spectroscopy and the naked eye as the signal readout, respectively. More importantly, the proposed molecule exchange process in the indicator displacement process could be successfully used to the fabrication of a calorimetric INHIBIT logic gate and even converted into a facile naked eye analysis through paper-based analytical, devices for conveniently and reliably detecting cysteine (CySH) in practical applications.