Grain-like chiral metal-organic framework/multi-walled carbon nanotube composited electrosensing interface for enantiorecognition of Tryptophan

Abstract

Due to the widespread application of chiral substances in current society, the electrochemical strategy to assemble chiral metal–organic frameworks (CMOFs) as sensors has shown great potential for sensitive enantiorecognition. In this paper, an efficient and highly selective electrochemical sensor was proposed based on multi-walled carbon nanotube (MWCNT) and CMOF, and successfully achieved sensitive chiral recognition of Tryptophan (Trp) enantiomers. Numerous MOFs in multiple synthesis conditions were investigated for a regular process to access the electrochemical chiral recognition. A variety of amino acids were introduced into the MOFs skeleton by a simple hydrothermal method for the enantio-specificity. Meanwhile the MWCNT smoothly integrated with the CMOF to form a functional electrosensing interface with the increase of conductivity. Based on the current ratio (Rcp) of tryptophan enantiomers by different modified electrodes, a series of experimental conditions were optimized for the optimal chiral recognition performance of the CMOF/MWCNT-based sensor, finally reaching 2.9 times of ΔIL/D between enantiomers. In addition, D/l-Trp showed a good linear relationship with the current in the range from 0.4 μM to 19 μM with the detection limit of 0.11 μM for l-Trp and 0.16 μM for d-Trp. The prepared composite-functionalized sensor owned the desired reproducibility and selectivity to identify Tryptophan enantiomers with robust chiral recognition. The research on the structure–activity relationship of chiral MOFs to Tryptophan enantiomers provides a new path to construct more electrochemical sensors for the application of enantiorecognition in pharmaceutical analysis.