Molecular recognition-based detoxification of aluminum in human plasma

Molecular recognition-based Al³⁺-imprinted poly(hydroxyethyl methacrylate-N-methacryloyl-L-glutamic acid) (PHEMAGA-Al³⁺) beads were prepared to be used in selective removal of Al³⁺ out of human plasma overdosed with Al³⁺ cations. The PHEMAGA-Al³⁺ beads were synthesized by suspension polymerization in the presence of a template-monomer complex (MAGA-Al³⁺). The specific surface area of PHEMAGA-Al³⁺ beads was found to be 55.6 m²/g on the average. The MAGA content in the PHEMAGA-Al³⁺ beads were found to be 640 μmol/g polymer. The template Al³⁺ cations could be reversibly detached from the matrix to form PHEMAGA-Al³⁺ using a 50 mM solution of EDTA. The Al³⁺-free PHEMAGA-Al³⁺ beads were then exposed to a selective separation procedure of Al³⁺ out of human plasma, which was implemented in a continuous system by packing the beads into a separation column (10 cm long with an inner diameter of 0.9 cm) equipped with a water jacket to control the temperature. The Al³⁺ adsorption capacity of the PHEMAGA-Al³⁺ beads decreased drastically from 0.76 mg/g polymer to 0.22 mg/g polymer as the flow rate was increased from 0.3 ml/min to 1.5 ml/min. The relative selectivity coefficients of the PHEMAGA-Al ³⁺ beads for Al³⁺/Fe³⁺, Al³⁺/Cu ²⁺ and Al³⁺/Zn²⁺ were found to be 4.49, 8.95 and 32.44 times greater than those of the non-imprinted PHEMAGA beads, respectively. FT-IR analyses on the synthesized PHEMAGA-Al³⁺ beads reveals monodentate and bidentate binding modes of Al³⁺ in complex with the carboxylate groups of the glutamate residues. Density functional theory computations at the B3LYP/6-31G(d,p) basis set suggests that structured water molecules play essential role in the stability of the monodentate binding mode in 1:1 PHEMAGA-Al³⁺ complexes. The PHEMAGA-Al³⁺ beads were recovered and reused many times, with no significant decrease in their adsorption capacities.