18β-Glycyrrhetinic acid derivative-based metallo-hydrogels with highly selective and sensitive for histidine detection

Quantitative detection of His has aroused great interest in disease diagnosis since abnormal histidine (His) metabolism would cause a variety of serious diseases. However, exploiting a strategy with facile, highly selective, sensitive sensing and low-cost to monitor His remains a challenge. In this study, a series of novel metallo-hydrogels were successfully constructed, which were composed of 18β-glycyrrhetinic acid (GA) derivative (GA-O-09) with rare earth metal ions (Ce³⁺, Tb³⁺, Eu³⁺ and La³⁺). In addition, these metallo-hydrogels possessed excellent thermodynamics stability with the gel melting temperature (T_gel) ranging from 62.4 ± 0.49 °C to 67.4 ± 0.49 °C and remarkable pH stability over a range of pH values of 3–10. Interestingly, the Histidine (His)-loaded GA-O-09/Eu³⁺ hydrogel and the His-loaded GA-O-09/La³⁺ hydrogel displayed extraordinary fluorescence enhancement, in which the lowest fluorescence response concentrations (LODs) of the His-loaded GA-O-09/Eu³⁺ hydrogel and the His-loaded GA-O-09/La³⁺ hydrogel were 1.14 × 10^-8 and 1.07 × 10^-8 M, respectively. Therefore, the result showed that the study of the GA-O-09/Eu³⁺ and GA-O-09/La³⁺ hydrogels could provide a potential application for highly selective and sensitive detection for His.