Minhua Feng

Effects of Tween 20 on the desorption of proteins from polymer surfaces

The effects of Tween 20 on the desorption of proteins from polyethylene and polyurethane were studied, using single protein solutions of the human proteins fibrinogen (Fb), immunoglobulin G (IgG), serum albumin (HSA), high density lipoproteins (HDL), and plasma. The surfactant may partly or even completely desorb the proteins, depending on the type of polymer and protein. About 40% of adsorbed HSA and 80% of adsorbed HDL from the corresponding single protein solutions were desorbed by Tween 20 from polyethylene, whereas Tween 20 had a small effect on the desorption of adsorbed Fb and IgG under the same conditions. However, the desorption of Fb and IgG by Tween 20 was much higher in the case of a diluted plasma solution compared to a pure protein solution. These findings may be explained by the differences of the interaction strengths between polymers and the adsorbed proteins. The displacement of HSA from polyethylene by Tween 20 occurred in the first few minutes and did not increase in time. It was also observed that preadsorbed Tween 20 was able to prevent in a large extent the adsorption of HSA onto polyethylene. Thus, the effect of Tween 20 on the desorption of protein is due to either the displacement of protein or prevention of protein adsorption onto the surfaces.

Iron(III) chelating resins-I. Preparation and properties of Sepharose-desferrioxamine gels

For the removal of iron(III), Sepharose-desferrioxamine gels were prepared by the coupling of CNBr-activated Sepharose with desferrioxamine (DFO) at pH 7.8-8.3. DFO densities of the gels were 12-23 mumol/ml gel with iron(III) chelating capacities of 8.5-18 mumol/ml gel. The Sepharose-DFO gels with a high affinity for iron(III) were used for the removal of iron(III) from aqueous iron(III) solutions, wine, milk and whey.

Iron(III) chelating resins II. 3-Hydroxy-4(1H)-pyridinones-sepharose gels.

3-Hydroxy-4(1H)-pyridinones(HP)-Sepharose gels were prepared to study their iron(III) chelating properties. As ligands, derivatives of 3-hydroxy-4(1H)-pyridinone were coupled to CNBr-activated Sepharose gels. HP-Sepharose gels were obtained with HP densities of 23-28 mumol/ml gel and iron(III) chelating capacities of 19-23 mumol/ml gel at pH 6.8. From preliminary experiments, it was found that with the gels 19-27% iron could be removed from milk. In addition, 74% of iron(III) was removed from 100% iron(III) saturated lactoferrin within 24 h at pH 6.8 in the presence of citrate and a Sepharose gel, onto which 1-(2-aminoethyl)-3-hydroxy-2-methyl-4(1H)-pyridinone had been immobilized as a ligand. The properties of the gels make them potentially useful as water-insoluble iron(III) chelating agents.

Iron(III)-chelating resins X. Iron detoxification of human plasma with iron(III)-chelating resins

Iron detoxification of human blood plasma was studied with resins containing desferrioxamine B (DFO) or 3-hydroxy-2-methyl-4(1H)-pyridinone (HMP) as iron(III)-chelating groups. The behaviour of four resins was investigated: DFO-Sepharose, HMP-Sepharose and crosslinked copolymers of 1-(s-acrylamidoethyl)-3-hydroxy-2-methyl-4(1H)-pyridinone (AHMP) with 2-hydroxyethyl methacrylate (HEMA) and of AHMP with N,N-dimethylacrylamide (DMAA). The efficiency of iron detoxification of plasma of the resins was mainly dependent on the affinity of the ligands and the hydrophilicity of the resins. The results of a stability study in phosphate-buffered saline at a physiological pH indicated that AHMP-DMAA was the most stable resin, whereas the Sepharose gels had a relatively lower stability. Experiments with the AHMP-DMAA resin showed that the resin was able to remove iron from plasma with different iron contents, and from plasma poisoned with FeCl3, iron(III) citrate or transferrin. A rapid removal from free serum iron was observed, whereas iron from transferrin was removed slowly afterwards. Only the overload iron was removed since in all cases the normal serum iron level of ca. 1 ppm was obtained.

Iron(III) chelating resins-IV. Crosslinked copolymer beads of 1-(B-acrylamidoethyl)-3-hydroxy-2-methyl-4(1H)-pyridinone (AHMP) with 2-hydroxyethyl methacrylate (HEMA)

Iron(III) chelating beads have been synthesized by copolymerization of 1-(s-acrylamidoethyl)-3-hydroxy-2-methyl-4(IH)-pyridinone (AHMP) with 2-hydroxyethyl methacrylate (HEMA), and ethyleneglycol dimethacrylate (EGDMA) as the crosslinking agent. The synthesis of the AHMP-HEMA beads was performed by suspension polymerization of AHMP, HEMA and EGDMA in benzyl alchol?20% aqueous NaCl solution using 2,2?-azobisisobutyronitrile (AIBN) as the initiator and polyvinylalcohol (40?88) as a suspending agent. The crosslinked copolymer beads were characterized by IR, and the AHMP content was determined by elemental analysis. The AHMP-HEMA beads were not too hydrophilic, and the copolymers absorbed at equilibrium only 40?50% water. It was found that the copolymer beads were very stable at 25°, but some degradation was observed at 121°. The AHMP-HEMA copolymers were able to chelate iron(III) and the chelation was dependent on the conditions such as pH and temperature. However, the capacities towards iron(III) chelation were always found to be much lower than the calculated values. The influence of the polymeric matrix on the iron(III) chelating ability was studied with iron(III) chelating resins containing various polymeric matrices. It was found that the iron(III) chelating efficiencies of the resins were strongly affected by their hydrophilicities. The low chelating efficiency of the AHMP-HEMA beads (0?40%) is probably due to their poor swelling in water.