Enantioselective fluorescent detection of lysine enantiomers by functionalized achiral metal organic frameworks

In this work, achiral metal organic frameworks (MIL-53(Al)–NH2) were synthesized and functionalized with poly (amidoamine) (PAMAM) dendrimers. By dispersing PAMAM grafted MIL-53(Al)–NH2 to water, the obtained solution exhibited high fluorescence intensity and stability. Due to the strong affinity interaction, fluorescence of the solution was quenched when Cu2+ was added. Following the addition of lysine to the system, the quenched fluorescence intensity was partially restored based on the chelation between Cu2+ and lysine. In this case, the fluorescent signal of MIL-53(Al)–NH2-PAMAM-Cu2+ system became turn-on state. Furthermore, because of different chelating abilities with L-lysine and D-lysine, the system exhibited enantioselective fluorescence enhancement. Therefore, the PAMAM grafted MIL-53(Al)–NH2 were successfully used for enantioselective fluorescence detection of lysine after being quenched by Cu2+. The method showed good linearity in both L/D-lysine detection (R2 = 0.9976–0.9984) and ee values determination (R2 = 0.9921). The detection limit of L-lysine and D-lysine were 7.52 and 12.2 μmol L−1, respectively. Reliability of the method was verified by analysis of lysine enantiomers in spiked drinking water samples. Rapid enantioselective fluorescent imaging of lysine enantiomers showed great application prospects in test paper, diagnostic kit and vivo imaging system.