Combining enzymatic hydrolysis with magnetic nanoparticles for resolution of chiral substances

Enantioseparation/Recognition based on nano techniques/materials

Enantiomers show different behaviors in interaction with the chiral environment. Due to their identical chemical structure and their wide application in various industries, such as agriculture, medicine, pesticide, food, and so forth, their separation is of great importance. Today, the term "nano" is frequently encountered in all fields. Technology and measuring devices are moving towards miniaturization, and the usage of nanomaterials in all sectors is expanding substantially. Given that scientists have recently attempted to apply miniaturized techniques known as nano-liquid chromatography/capillary-liquid chromatography, which were originally accomplished in 1988, as well as the widespread usage of nanomaterials for chiral resolution (back in 1989), this comprehensive study was developed. Searching the terms "nano" and "enantiomer separation" on scientific websites such as Scopus, Google Scholar, and Web of Science yields articles that either use miniaturized instruments or apply nanomaterials as chiral selectors with a variety of chemical and electrochemical detection techniques, which are discussed in this article.

Influence of Host-Guest Interaction between Chiral Selectors and Probes on the Enantioseparation Properties of Graphene Oxide Membranes

Graphene oxide (GO)-based membranes have displayed superior performances in the chiral resolution compared with conventional polymer-based and inorganic membranes. However, the effect of the host-guest interaction between chiral selectors and probes on the enantioseparation properties of GO-based membranes remains to be established. In this work, l-phenylalanine (l-Phe, as the chiral selector)-modified GO-based (l-Phe-GO) membranes were fabricated, and their enantioseparation performances toward various enantiomers, that is, d- and l-phenylalanine (d- and l-Phe), d- and l-methionine (d- and l-Met), N-acyl-d-phenylalanine (N-acyl-d-Phe) and N-acyl-l-phenylalanine (N-acyl-l-Phe), and N-acyl-d-methionine (N-acyl-d-Met) and N-acyl-l-methionine (N-acyl-l-Met), were detected. Results show that (i) l-Phe is preferential to transport d-enantiomers relative to l-enantiomers; (ii) as far as d-enantiomers are concerned, the d-Phe-like enantiomers move faster than d-Met-like ones through the l-Phe-GO membrane owing to their different host-guest interactions. The strength of interactions between chiral selectors and probes was further confirmed from both experimental and theoretical standpoints. In the former case, the enantioselective adsorption of l-Phe-GO nanosheets toward the aforementioned enantiomers demonstrates that l-Phe delivers a higher adsorption capacity to d-enantiomers relative to l-enantiomers, and meanwhile, d-Phe-like enantiomers are better than d-Met-like enantiomers in the adsorption capacity. In the latter case, the chiral separation mechanism is clarified using the periodical density functional theory (DFT) calculation, indicating that l-Phe interacts with d-enantiomers more strongly than l-enantiomers. Especially, our calculations unveil that the difference in the interaction strength is principally dominated by the nonstereoselective interactions between chiral probes and the GO surface. Therefore, our findings suggest that the nonstereoselective weak interaction can be employed to improve the enantioselectivity of GO-based membranes.