Molecularly imprinted cryogel for L-glutamic acid separation

Abstract

A molecular recognition based L-glutamic acid (L-GLU) imprinted cryogel was prepared for L-GLU separation via chromatographic applications. The novel functional monomer N-methacryloyl-(L)-glutamic acid-Fe3+ (MAGA-Fe3+) was synthesized to be complex with L-GLU. The L-GLU imprinted cryogel was prepared by free radical polymerization under semifrozen conditions in the presence of a monomer-template complex MAGA-Fe3+-L-GLU. The binding mechanism of MAGA-Fe3+ and L-GLU was characterized by Fourier transform infrared (FTIR) spectroscopy in detail. FTIR analyses on the synthesized MAGA-Fe3+-GLU complex reveals bridging bidentate and monodentate binding modes of Fe3+ in complex with the carboxylate groups of the glutamate residues. The template L-GLU could be reversibly detached from the cryogel to form the template cavities using a 100 mM solution of HNO3. The amount of adsorbed L-GLU was detected using the phenyl isothiocyanate method. The L-GLU adsorption capacity of the cryogel decreased drastically from 11.3 to 6.4 mu mol g-1 as the flow rate increased from 0.5 to 4.0 mL min-1. The adsorption onto the L-GLU imprinted cryogel was highly pH dependent due to electrostatic interaction between the L-GLU and MAGA-Fe3+. The PHEMAGA-Fe3+-GLU cryogel exhibited high selectivity to the corresponding guest amino acids (i.e., D-GLU, L-ASN, L-GLN, L-, and D-ASP). Finally, the L-GLU imprinted cryogel was recovered and reused many times, with no significant decrease in their adsorption capacities