A new ensemble approach based chemosensor for the reversible detection of bio-thiols and its application in live cell imaging

Based on an aldazine-copper chemosensing ensemble (NP-Cu²⁺), a new fluorescence chemosensor for the detection of biothiols (Cys, Hcy and GSH) was designed and synthesized. In aqueous solution, the ligand NP exhibited high selectivity toward Cu²⁺ ions by forming a 2:1 complex, accompanied with a dramatic fluorescence quenching and a notable bathochromic-shift of the absorbance band. Due to the high affinity of thiols and copper, the specific interaction of thiols (Cys, Hcy and GSH) with NP-Cu²⁺ ensemble led to the liberation of the NP. As the result, recovery of fluorescence and UV-vis absorbance was observed. The detection limits of NP-Cu²⁺ to Cys, Hcy and GSH were estimated to be 1.5 μM, 1.8 μM and 2.2 μM, respectively. The fluorescence "OFF-ON" circle can be repeated to a minimum of 5 times by the alternative addition of thiols and Cu²⁺, implying that NP-Cu²⁺ is a recyclable chemosensor for thiols. Results of fluorescence microscopy imaging suggested that NP-Cu²⁺ has potential to be used as a powerful tool for the detection of intracellular thiols.