An electrochemical sensor based on metal-organic framework-chiral ionic liquid composites for the enantiorecognition of tryptophan enantiomers

Tryptophan (Trp) is an essential amino acid in the human body, and the dysregulation of l-tryptophan (l-Trp) can cause nervous system dysfunction, while d-tryptophan (d-Trp) is involved in the composition of some anticancer agents or cancer treatment drugs. Identification and detection of Trp enantiomers are of great value in clinical diagnosis, biomedicine, and other fields. In this work, an electrochemical chiral sensor Fe-MIL-88-NH₂ metal-organic framework-chiral ionic liquid/multi-walled carbon nanotube-MXene-chitosan/glassy carbon electrode (Fe-CIL/MWCNTs-MXene-CS/GCE) is proposed for the chiral recognition of Trp enantiomers (l/d-Trp). The chiral ionic liquid 1-ethyl 3-methylimidazole l-tartrate (CIL) was assembled on the surface of Fe-MIL-88-NH₂ metal-organic framework to synthesize the chiral recognition material Fe-CIL, which not only has chiral recognition properties and hydrophilicity but also excellent mechanical properties. The asymmetrical spatial structure of Fe-CIL provides the feasibility for the chiral recognition of l/d-Trp. In addition, differential pulse voltammetry (DPV) was used as the detection method and the DPV peak potential difference (ΔE_p) of l/d-Trp is referred to as the index of the chiral recognition performance. Moreover, even in the real sample, the percentage of d-Trp (d-Trp%) in the Trp mixture maintained a good linear relationship with the DPV peak potential (E_p), and this electrochemical chiral sensor showed good reproducibility, stability, and chiral recognition ability. Furthermore, the proposed sensor Fe-CIL/MWCNTs-MXene-CS/GCE has great potential in the field of chiral molecule recognition and determination.