Abstract
Molecularly imprinted thermoresponsive hydrogels for dopamine recognition were synthesized using N-isopropylacrylamide as the temperature-sensitive element, methacrylic acid or itaconic acid as functional monomer and N,N’-methylenebisacrylamide or ethylene glycol dimethacrylate as crosslinking agent. The stoichiometry of the template–functional monomer prepolymerization complexes was determined by 1H NMR experiments according to the Job method of continuous variation as well as signal line width analysis. It was found that dopamine hydrochloride forms complexes with methacrylic acid and itaconic acid with 1:3 and 2:3 template to functional monomer stoichiometry, respectively. Hydrogels composed of itaconic acid and with appropriate template content revealed the highest efficiency of imprinting process and relatively high selectivity of dopamine hydrochloride rebinding in water near the phase transition temperature.
Highlights
Molecular imprinting (MI) into organic polymers, first reported by Wulff and Sarhan [1], nowadays is widely reported technique of preparing polymeric materials with molecular recognition elements
Theoretical analysis of the intermolecular interactions in the prepolymerization complexes between dopamine hydrochloride and functional monomers in different solvent was reported by Lulinski et al [12]
1H NMR analyses of the prepolymerization complexes formed between methacrylic acid or itaconic acid and dopamine hydrochloride (MAc-D and ItAc-D) in deuterated Dimethyl sulfoxide (DMSO) were performed
Summary
Selection of appropriate monomers and porogen (solvent in which complexes are formed) seems to be crucial in noncovalent imprinting. Additional difficulty of this method inheres in proper monomer–template ratio fitting. Equimolar solutions (0.04 M) of carboxylic acid and dopamine hydrochloride in DMSO-d6 were prepared, respectively, dried over molecular sieves (4 A ) and distributed among 11 NMR tubes in such a way that the ratios of monomer and templates varied between 0:1 and 1:0 (with a constant sample volume of 0.7 mL). In order to determine the swelling ratio (S) of non-imprinted hydrogels, the dried samples were immersed in water at specific temperature until equilibrium was confirmed (usually 48 h). All experiments were performed at given temperature in triplicate, and data were expressed as the mean ± standard deviation
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