DNA-Modified Polysulphone Microspheres for Endocrine Disruptors and Heavy Metal Ions Removal

Porous polysulphone (PSf) microspheres were modified by blending DNA into them and immobilizing DNA onto their surfaces. The DNA-modified microspheres, which were stable in water, were then used to remove endocrine disruptors and heavy metal ions from their aqueous solutions. Such microspheres could effectively accumulate pollutant compounds and endocrine disruptors, such as ethidium bromide, Acridine Orange, biphenyl, dibenzofuran and dibenzo- p-dioxin from their aqueous solutions. PSf microspheres without DNA also accumulated and removed endocrine disruptors due to their porosity and the hydrophobic interaction between the endocrine disruptors and PSf. Endocrine disruptors with and without a planar structure were effectively accumulated and removed by the DNA-modified PSf microspheres. In addition, PSf microspheres were found to be capable of selectively removing heavy metal ions such as Zn2+, Cu2+, Mg2+, Cd2+ and Ag+ from their aqueous solutions. These results show that DNA can be used to modify PSf microspheres, with the DNA-modified microspheres having a potential use in environmental applications.

Immobilized metal affinity beads for ferritin adsorption

A new metal-chelate adsorbent utilizing N-methacryloyl-(L)-cysteine methyl ester (MAC) was prepared as a metal-chelating ligand. MAC was synthesized by using methacryloyl chloride and L-cysteine methyl ester dihydrochloride. Spherical beads with an average diameter of 150-200 microm were produced by suspension polymerization of 2-hydroxyethyl methacrylate (HEMA) and MAC carried out in an aqueous dispersion medium. Then, Fe(3+) ions were chelated directly on the beads. Properties such as specific surface area, specific pore volume and ligand occupation were determined. The specific surface area of the beads was found to be 18.9 m2/g. The total pore volume was 2.8 ml/g and represented a porosity over 52%. The average pore size of the poly(HEMA-MAC) beads was 620 nm. Fe(3+)-chelated beads were used in the adsorption of ferritin from aqueous solutions. Ferritin adsorption increased with increasing ferritin concentration. The maximum ferritin adsorption capacity of the Fe(3+)-chelated poly(HEMA-MAC) beads (Fe(3+) loading 0.81 mmol/g) was found to be 3.7 mg/g at pH 4.0 in acetate buffer. The non-specific ferritin adsorption on the poly(HEMA-MAC) beads were 0.4 mg/g. Adsorption behavior of ferritin could be modelled using both the Langmuir and Freundlich isotherms. Adsorption capacity decreased with increasing ionic strength of the binding buffer. Ferritin molecules could be adsorbed and desorbed five times with these adsorbents without noticeable loss in their ferritin adsorption capacity.

Lead electrocapture on hydroxyapatite coated electrodes

Hydroxyapatite coated electrodes were made by a hydrolysis reaction involving silanes and hydroxyapatite particles on stainless steel. Aqueous lead ions were captured on the coatings with or without electromigration. Results depend on coating thickness, supporting electrolyte and the presence of the electric field. It was found that this new electrocapture method can remove lead from solutions down to ppb levels.