Synthesis and study of chelating polymers and their application to protein and metal separation from aqueous solutions using novel metal affinity interaction techniques

Abstract

The main objective of this research work was the development, synthesis, and study of polymeric chelating derivatives. These derivatives were characterized in terms of their specific metal affinity interaction with biomolecules and metal ions. These engineered materials were used to test their feasibility as tools for separation of proteins and heavy metal ions from aqueous solutions using different affinity separation techniques. Linear and branched polymers were synthesized to create a variety of materials. Among the linear polymers synthesized was the chelated monomethoxy poly(ethylene) glycol (PEG-IDA). This derivative was used in metal affinity partitioning and metal affinity electrophoresis for fast protein-metal interaction analysis. Also a linear heterobifunctional poly(ethylene) glycol (Biotin - PEG - IDA) was synthesized and used as a tool to develop a modified enzyme-linked immuno sorbent assay (ELISA). A multi-armed high molecular weight chelating poly(ethylene) glycol (Star PEG-IDA) was prepared to enhance the separation of protein mixture in gel permeation chromatography. Iminodiacetic poly(ethyleneimine) (PEI-IDA) was prepared and used as a soluble chelating polymer in complexation-ultrafiltration studies for heavy metal ion removal from aqueous solutions. Similar PEIs were also used as casting polymers for the synthesis of affinity adsorbents useful in chromatographic applications. Either as a soluble macromolecule or as a casting polymer for the preparation of adsorbents, PEI chelated derivatives were used for ultratrace metal ion preconcentration and metal ion separations. All polymeric materials prepared were characterized using analytical techniques which include elementary analysis, atomic absorption, UV and IR spectroscopy, high performance liquid chromatography and several colorimetric assays for the determination of end groups and product purity. Metal affinity separation techniques studied with the aforementioned derivatives included: affinity partitioning, affinity electrophoresis and affinity size exclusion for protein purification; affinity complexation-ultrafiltration and metal ion affinity chromatography for removal of heavy metal. Efficient separation of protein mixtures were achieved based on selective affinity by some of the chelated polymers here described and extremely high metal adsorption capacities were found for some of the PEI-based adsorbents prepared. Even though, some of these techniques are still in developmental stages, the results are very promising and encouraging for biotechnical and environmental applications.