Peptide-based fluorescent chemical sensors for the specific detection of Cu²⁺ and S²⁻

Cu²⁺ and S²⁻ play important roles in our environment, so it is beneficial to develop sensors capable of detecting Cu²⁺ and S²⁻ in biological samples. To accomplish this goal, a new peptide-based fluorescent chemical sensor L (FITC-Ahx-His-Glu-Phe-Cys-NH₂) has been designed and synthesized. It can specifically recognize Cu²⁺ by forming a L-Cu complex which can quench the fluorescence of L. The subsequent addition of S²⁻ can remove Cu²⁺ from the L-Cu complex, thereby restoring the fluorescence in a process described as an “On-Off-On” cycle. Cu²⁺ and S²⁻ can be detected by L with extremely high sensitivity and the detection limits is 32 nM and 53 nM respectively. Additionally, the sensor L can detect Cu²⁺ and S²⁻ at physiological pH conditions. The result of this research is the development of a peptide-based fluorescent chemical sensor L, which can specifically detect Cu²⁺ and S²⁻ in the environment.