Theoretical Insight into the Interaction between Chloramphenicol and Functional Monomer (Methacrylic Acid) in Molecularly Imprinted Polymers

Abstract

Molecular imprinting technology is a promising method for detecting chloramphenicol (CAP), a broad-spectrum antibiotic with potential toxicity to humans, in animal-derived foods. This work aimed to investigate the interactions between the CAP as a template and functional monomers required for synthesizing efficient molecularly imprinted polymers for recognition and isolation of CAP based on density functional theory. The most suitable monomer, methacrylic acid (MAA), was determined based on interaction energies and Gibbs free energy changes. Further, the reaction sites of CAP and MAA was predicted through the frontier molecular orbitals and molecular electrostatic potentials. Atoms in molecules topology analysis and non-covalent interactions reduced density gradient were applied to investigate different types of non-covalent and inter-atomic interactions. The simulation results showed that CAP was the main electron donor, while MAA was the main electron acceptor. Moreover, the CAP-MAA complex simultaneously involved N-H···O and C=O···H double hydrogen bonds, where the strength of the latter was greater than that of the former. The existence of hydrogen bonds was also confirmed by theoretical and experimental hydrogen nuclear magnetic resonance and Fourier transform infrared spectroscopic analyses. This research can act as an important reference for intermolecular interactions and provide strong theoretical guidance regarding CAP in the synthesis of molecularly imprinted polymers.

Keywords: chloramphenicol; density functional theory; intermolecular interaction; methacrylic acid; molecularly imprinted polymers.

Figure 1

Interaction energies (ΔE) and Gibbs free energy changes (ΔG) of chloramphenicol+methyl methacrylate (CAP+MMA), chloramphenicol+acrylamide (CAP+AM), chloramphenicol+acrylic acid (CAP+AA), chloramphenicol+methacrylic acid (CAP+MAA) complexes.

Figure 2

Solvation energy of CAP and MAA in different solvents.

Figure 3

Frontier molecular orbitals (FMOs) and energy levels for highest occupied molecular orbitals (HOMOs) (top) and lowest unoccupied molecular orbital (LUMOs) (bottom) of the template CAP and monomer MAA.

Figure 4

Molecular electrostatic potential (MEP) maps of CAP and MAA.

Figure 5

Topological atoms in molecules (AIM) graph of the CAP–MAA complex.

Figure 6

(a) Non-covalent interaction (NCI) scatter diagram and (b) reduced density gradient (RDG) analysis of the CAP–MAA complex.

Figure 7

Theoretical and experimental fourier transform infrared spectroscopic (FTIR) of (a) functional monomer MAA, (b) template CAP, and (c) CAP–MAA complex.

Figure 8

Theoretical and experimental ¹H-NMR spectra of MAA, template CAP, and the CAP–MAA complex.