Computational and spectroscopic study of the prepolymerization complex formation in the tetracycline-based imprinted polymer synthesis

In this work, the capacity of four functional monomers such as (3-aminopropyl)triethoxysilane (APTES), 3-amino propyltrimethoxysilane (APTMS), 3-(2-aminoethyl)-3-aminopropyltriethoxysilane (AEAPTES) and 3-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AEAPTMS) to bind tetracycline (TC) and to form a noncovalent prepolimerization complex is evaluated by a DFT-based methodology. The investigation was carried out using quantum chemical calculations at B3LYP level of theory with the 6-311G(d,p) basis set. The computational model was used to determine the optimized geometry of the structures of TC template, monomers and TC-monomer complexes at different TC:monomer stoichiometric ratios. The changes in the binding energy (ΔE) due to complex formation were determined. The results demonstrated the formation of stable TC-monomer complexes through an electrostatic interaction with the donation of an H atom from the TC to the monomer and intermolecular H-bonds between groups of TC and functional monomers. APTMS and APTES monomers showed the most stable complexes with TC (-38.45 and -43.31 kcal/mol). Theoretically, solvent effects on the stability of the prepolymerization complexes was considered using the solvent model based on the solute electron density (SMD). Spectroscopic analysis using UV-Vis, fluorescence, and 1HNMR spectroscopy corroborate the TC-APTES prepolymerization complex. After the rational design, the MIPs based on APTES and AEAPTMS were synthesized and rebinding performance was evaluated, showing high adsorption capacity for the MIP based on APTES monomer. DFT calculations are in excellent agreement with experimental results.