A choline chloride-acrylic acid deep eutectic solvent polymer based on Fe3O4 particles and MoS2 sheets (poly(ChCl-AA DES)@Fe3O4@MoS2) with specific recognition and good antibacterial properties for ß-lactoglobulin in milk.

With the development of deep eutectic solvents (DESs), more DES-based functional materials have been explored and applied in various areas. In this work, a novel choline chloride-acrylic acid (ChCl-AA) DES polymer, on a 2D magnetic base, was prepared for the recognition of ß-lactoglobulin (ß-LG) biomacromolecules in milk and for the inhibition of common bacteria such as Escherichia coli (E. coli), Pseudomonas fluorescens (P. fluorescens), Staphylococcus aureus (S. aureus), and Bacillus subtilis (B. subtilis). The ChCl-AA DESs were polymerized on the surface of 2D MoS2 sheets doped with nano Fe3O4 particles, and the resulting polymer was abbreviated poly(ChCl-AA DES)@Fe3O4@MoS2. The free energy (ΔG=-92) of ChCl-AA DES was calculated using the Gaussian software, the composition and structure of poly(ChCl-AA DES)@Fe3O4@MoS2 were characterized by field emission scanning electron microscopy, transmission electron microscopy, etc., the qualitative and quantitative analyses of ß-LG were done by fluorescence spectra, sodium dodecyl sulfate polyacrylamide gel electrophoresis and high performance liquid chromatography, and the bioactivity of bacteria was analyzed by flat colony counting. Based on the present analysis, poly(ChCl-AA DES)@Fe3O4@MoS2 specifically recognized ß-LG in a good fitting Langmuir isotherm (R2 = 0.9909) and second-order kinetic model (R2 = 0.9989) by affinity, and evidently inhibited three bacteria, namely, E. coil (65%), S. aureus (50%), and B. subtilis (54%), effectively reducing the relative colony number. As the poly(ChCl-AA DES)@Fe3O4@MoS2 material did not only exhibit specific recognition of biomacromolecules, but also had an antimicrobial effect against common bacteria, it could be an ideal separation media or carrier for biomacromolecules in real samples.

Specific recognition of polyphenols by molecularly imprinted polymers based on a ternary deep eutectic solvent.

Typically, a target compound is selected as a template for a molecularly imprinted polymer (MIP); however, some target compounds are not suitable as templates because of their poor solubility. Using the tailoring properties of a deep eutectic solvent (DES), the insoluble target compound caffeic acid was transformed into a ternary choline chloride-caffeic acid-ethylene glycol (ChCl-CA-EG) DES, which was then employed as a template to prepare MIPs. The ternary DES-based MIPs were characterized by Fourier transform infrared spectroscopy, elemental analysis, scanning electron microscopy, and atomic force microscopy. The effects of time, temperature, ionic strength, and pH on the recognition processes for four polyphenols (caffeic acid, protocatechuic acid, catechin, and epicatechin) by 13 ChCl-CA-EG ternary DES-based MIPs was investigated using high-performance liquid chromatography. The recognition specificity of the MIPs for CA was significantly better than that for the other polyphenols, and the MIPs exhibited obvious characteristics of chromatographic packing materials. In addition, the recognition processes mainly followed a second-order kinetics model and the Freundlich isotherm model, which together indicated that the MIPs mainly recognized the polyphenols by chemical interactions including ion exchange, electron exchange, and new bond formation. Furthermore, the specific recognition ability of the MIPs for polyphenols, which was better than those of C18, C8, or non-molecularly imprinted polymer adsorbents, was successfully applied to the recognition of polyphenols in a Radix asteris sample. The transformation of an insoluble target compound in a polymeric DES for MIP preparation and recognition is a novel and feasible strategy suitable for use in further MIP research developments.

Ternary choline chloride/caffeic acid/ethylene glycol deep eutectic solvent as both a monomer and template in a molecularly imprinted polymer.

A molecularly imprinted polymer based on a ternary deep eutectic solvent comprised of choline chloride/caffeic acid/ethylene glycol was prepared. The caffeic acid in the ternary deep eutectic solvent was used as both a monomer and template. The molecularly imprinted polymer based on the ternary deep eutectic solvent was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, field-emission scanning electron microscopy, Brunauer-Emmett-Teller surface area analysis, atomic force microscopy, and elemental analysis. A series of molecularly imprinted polymers based on choline chloride/caffeic acid/ethylene glycol with different molar ratios was prepared and applied to the molecular recognition of polyphenols. A comparison of the recognition ability of molecularly imprinted polymers to polyphenols revealed that the choline chloride/caffeic acid/ethylene glycol (1:0.4:1, molar ratio) molecularly imprinted polymer had the best molecular recognition effect with 132 µg/g of protocatechuic acid, 104 µg/g of catechins, 80 µg/g of epicatechin, and 123 µg/g of caffeic acid in 6 h, as well as good molecular recognition ability for polyphenols from a Radix Asteris sample. These results show that the ternary deep eutectic solvent based molecularly imprinted polymer is a potential medium that can be applied to drug purification, drug delivery, and drug analysis.