A novel peptide fluorescent chemical sensor capable of detecting Cu²⁺, Zn²⁺, and S²

A novel peptide-based chemical fluorescence sensor L (Dansyl-His-Pro-Thr-Cys-NH₂) was designed and synthesized. This sensor exhibits an "On-Off-On" detection cycle to detect Cu²⁺, Zn²⁺, and S^2- in solution. According to the chelation-enhanced fluorescence (CHEF) mechanism, when Zn²⁺ is present, the fluorescence is significantly enhanced and a blue shift occurs, representing a "Turn-On" phase of the fluorescence detection mode. Because copper ions (Cu²⁺) have a paramagnetic quenching sensing mechanism, the fluorescence of L quenches rapidly with the formation of the L-Cu system, representing the "Turn-Off" phase. The subsequent introduction of S^2- to the L-Cu system results in the recovery of the L-fluorescence, thereby representing the second "Turn-On" phase. As a peptide molecule, the sensor L has several advantages over other types of sensors, including water solubility, high sensitivity, and good biocompatibility, with a very low detection limit. The detection lines of Zn²⁺ and Cu²⁺ are 97 nM (R = 0.993) and 75 nM (R = 0.995), respectively. Additionally, the sensor does not exhibit any obvious cell toxicity. These results indicate that this peptide chemiluminescent sensor has the potential to be applied in in vivo detection.