Evaluation of selective composite cryogel for bromate removal from drinking water.

Bromate, which is a potential carcinogen, should be removed from drinking water to levels of less than 10 microg/L. A chitosan-based molecularly imprinted polymer (MIP) and a sol-gel ion-exchange double hydrous oxide (Fe(2)O(3) x Al(2)O(3) x xH(2)O) adsorbent (inorganic adsorbent) were prepared for this purpose. The sorption behavior of each adsorbent including sorption kinetics, isotherms, effect of pH and selective sorption were investigated in detail. Sorption experimental results showed that the MIP adsorbents had better selectivity for bromate, even in the presence of high concentrations of nitrate, as compared to the inorganic adsorbent. It was found that pH does not affect the adsorption of bromate when using the inorganic adsorbent. Additionally, both adsorbents were immobilized in a polymeric cryogel inside plastic carriers to make them more practical for using in larger scale. Regeneration of the cryogels either containing MIP or inorganic adsorbents were carried out by 0.1 M NaOH and 0.1 M NaCl, respectively. It was found that the regenerated MIP and inorganic adsorbents could be used at least three and five times, respectively, without any loss in their sorption capacity.

Affinity precipitation of proteins using metal chelates.

Metal affinity precipitation has been successfully developed as a simple purification process for the proteins that have affinity for the metal ions. The copolymers of vinylimidazole with N-isopropylacrylamide are easily synthesized by radical polymerization. When loaded with Cu(II) and Ni(II) ions, these copolymers are capable of selectively precipitating proteins with natural metal-binding groups or histidine-tagged recombinant proteins.

Affinity processing of cell-containing feeds using monolithic macroporous hydrogels, cryogels.

Monolithic macroporous hydrogels, "cryogels," are produced by polymerization in a partially frozen state when the ice crystals perform as a porogen. Cryogels have a unique combination of properties: (i) large (10-100 microm) pores; (ii) minimal non-specific interactions due to the hydrophilic nature of the polymers; (iii) porosities exceeding 80-90%; (iv) good mechanical stability. These properties of cryogels allow for their application for direct capture of extracellularly expressed histidine-tagged protein from the fermentation broth and separation of different cell types.

Metal-chelate affinity precipitation of proteins using responsive polymers.

Affinity precipitation of proteins uses polymers capable of reversible soluble-insoluble transitions in response to small environmental changes (temperature, pH or solvent composition). Here we describe protocols for (i) the synthesis of responsive polymers with specific affinity to target proteins and (ii) the purification of proteins using these polymers. The purification is based on precipitation of the affinity complex between the protein and the polymer, which is induced by environmental changes. This separation strategy is simpler and more cost effective than conventional affinity column chromatography. Specifically, we describe the synthesis of thermoresponsive 1-vinylimidazole:N-isopropylacrylamide copolymers. The whole procedure takes 2-3 h when applied to purification of recombinant His-tag proteins or proteins with natural metal binding groups by means of metal chelate affinity precipitation. Optimization of the polymer composition and the type of chelating ions allows for target protein yields of 80% and higher.

Characterization of a continuous supermacroporous monolithic matrix for chromatographic separation of large bioparticles.

A continuous supermacroporous monolithic chromatographic matrix has been characterized using a capillary model, experimental breakthrough curves, and pressure drop experiments. The model describes the convective flow and its dispersive mixing effects, mass transfer resistance, pore size distribution, and the adsorption behavior of the monolithic matrix. It is possible to determine an effective pore size distribution by fitting the capillary model to experimental breakthrough curves and pressure drop experiments. The model is able to describe the flow rate dependence of the experimental breakthrough curves. Mass transport resistance was due to: (i) dispersive mixing effects in the convective flow in the pores; and (ii) slow diffusion in the stagnant film covering the surface within each pore, under adsorption conditions. The monolithic matrix can be described by a very narrow pore size distribution, illustrating one of the advantages of the gel. A broader pore size distribution results in increased band broadening. This can be studied easily using the model developed in this investigation.