Specific chiral recognition of amino acid enantiomers promoted by an enzymatic bioreactor in MOFs

Abstract

Chiral recognition and quantification of amino acid (AA) enantiomers are of great significance in many fields such as biology and biomedicine. Herein, a general enzyme-driven fluorescence sensing model is proposed to achieve this goal. The designed fluorescent probes consist of three components: a natural enzyme for enantioselective and chemoselective recognition, a borate ester-based fluorescent molecule as a fluorescent response reporter, as well as an ordered mesoporous Ce-based MOF (OMUiO-66(Ce)) for the integration of an enzyme and fluorescent reporter as a cascade response system. In the presence of L-AA oxidase, the sensory platform exhibited highly efficient L-type enantioselectivity toward a series of common AAs and the enantioselective enhancement ratios (ef or ΔI_L/ΔI_D) reached 212 for phenylalanine (Phe), 213 for leucine, 194 for tryptophan and so on. Furthermore, using a specific AA oxidase of L-glutamate oxidase was also exemplified to ensure the rapid quantification of L-glutamate (L-Glu) among numerous free amino acids with high enantioselectivity and chemoselectivity. The specificity of probes toward AA enantiomer recognition was scarcely disturbed by other possibly coexistent interfering species. The direct checking of L-Phe and L-Glu from mixed AA enantiomers in simulated body fluid samples was successfully achieved, indicating their great potential for the high-throughput screening of specific chiral AAs in complex biological samples.