Conjugated polymer with carboxylate groups-Hg^{2 +} system as a turn-on fluorescence probe for label-free detection of cysteine-containing compounds

In this work, a turn on fluorescent sensor, based on Hg^{2 +} coordination conjugated polymer, was developed to detect cysteine-containing compounds. The fluorescence of conjugated polymer (poly(2,5-bis (sodium 4-oxybutyrate) -1,4 - phenylethynylene-alt-1,4-phenyleneethynylene; PPE-OBS) would be quenched by Hg^{2 +} because of the coordination-induced aggregation and electron transfers of PPE-OBS toward Hg^{2 +}. When there were some cysteine-containing compounds in PPE-OBS-Hg^{2 +} system, the fluorescence of PPE-OBS would be recovered. It indicated that the PPE-OBS-Hg^{2 +} system could be used to detect cysteine-containing compounds. Under the optimized conditions, the experiment results showed that there were particularly linear range, high sensitivity and selectivity over other amino acids. The limit of detection (LOD) of cysteine (Cys), homocysteine (Hcy) and glutathione (GSH) were 0.725 μmol L^{− 1}, 0.982 μmol L^{− 1} and 1.21 μmol L^{− 1} by using this sensor. In addition, Cys standard recovery in several green tea drink and honey samples was also demonstrated. The recovery of Cys was range from 96.3 to 105.0% and RSD was less than 3.25%. The satisfactory results demonstrated that the proposed method could be as a potential fluorescent method for determining cysteine-containing compounds in real samples.