Porous Gel Beads Research Articles

A renewable and functionalized chitosan gel bead for statically and dynamically capturing aquatic Hg(II) with a prominent capacity

Porous gel beads have aroused considerable interest in the field of wastewater treatment because of their enhanced adsorption capacity and ease of separation. Herein, a facile yet efficient method to synthesize porous chitosan gel beads (PBCSB) through the amide reaction and integrated with a porogenic process was proposed and further optimized. The well-preserved honeycomb internal structure was beneficial for aquatic Hg(II) to approach the surface and diffuse into the interior of the gel beads. The as-prepared adsorbent at a diameter of 3–5 mm possessed ultra-high adsorption ability (1139.82 mg g−1) toward Hg(II), declining the concentration from 500 mg L-1 to 0.017 mg L-1. Furthermore, the PBCSB could attain a high removal Hg(II) rate (>80%) even at pH 1 and maintained excellent Hg(II) adsorption performance (94.24%-99.99%) within five regeneration cycles. In the multi-component solution, the Kd of Hg(II) was 4–5 orders of magnitude higher in comparison with that of others. The superior adsorption performance was attributed to the complexation between Hg(II) and the functional groups involving sulfur, nitrogen, and oxygen based on the XPS analysis and density functional theory (DFT) calculation. The fixed-bed column filled with PBCSB exhibited a stable and satisfactory performance under different conditions. The findings confirmed the inherent superior performance, renewability, and application potential for selective capture Hg(II) from real industrial wastewater.

Insight: High intensity and activity carrier granular sludge cultured using polyvinyl alcohol/chitosan and polyvinyl alcohol/chitosan/iron gel beads

The newly developed carrier granular sludge (CGS) with polyvinyl alcohol/chitosan (PVA/CS) and PVA/CS/Fe gel beads assistance showed higher intensity and anammox activity than the natural granular sludge (NGS). Through comprehensive investigation, it was found: (1) the gel beads provided a stable framework of cells entangle with extracellular polymeric substances (EPS) to enhance the sludge intensity. In this framework, β-polysaccharides are distributed at the edge of CGS as a protection layer, α-polysaccharides and proteins are spread in the whole cross-section as backbones, and Fe2+/Fe3+ in CGS-PVA/CS/Fe act as bridges to link with the negatively charged groups on bacterial surfaces and proteins. (2) The porous gel beads satisfied a relatively unimpeded mass transfer. Thus, the sludge activity, microbe’s metabolism, membrane transportation and environmental adaption in CGS were apparently improved. The results improved the understanding about the advantages of the CGS and indicated their possible application in full-scale anammox processes.

Preparation of sugarcane bagasse succinate/alginate porous gel beads via a self-assembly strategy: Improving the structural stability and adsorption efficiency for heavy metal ions

Sugarcane bagasse, a kind of agricultural waste, was esterified by mechanical activation-assisted solid phase reaction with succinic anhydride as esterifying agent to prepare SB succinate (SBS) with rich carboxyl and ester functional groups. The layer-by-layer (LbL) self-assembly technology was used to prepare SBS/alginate (Alg) porous gel beads (SAPGB) with outstanding mechanical strength and desired porous structure from external surface to interior through the formation of gel network structure of SBS/Ca2+/Alg. The adsorption kinetics and isotherm indicated that the adsorption of metal ions onto SAPGB followed the pseudo-second-order kinetics and Langmuir isotherm mode (Qmax = 354.60 and 176.36 mg g−1 for Pb2+ and Cd2+, respectively). The adsorption behavior of SAPGB for metal ions was mainly amonolayer chemical adsorption process. The adsorption was fast and reached equilibrium within 60 min, ascribed to rapid diffusion from porous surface into internal pores. In addition, the stable SAPGB adsorbent exhibited excellent regeneration performance.

Preparation of nanogel-immobilized porous gel beads for affinity separation of proteins: fusion of nano and micro gel materials

We describe the preparation and evaluation of nanogel-immobilized porous gel beads (GB) for application as a protein purification medium. Nanogel particles (NP) that bind with the Fc fragment of immunoglobulin G (IgG) were immobilized on the pore surface of macroporous hard GB containing quaternary ammonium cations on the surface via multipoint electrostatic interactions. The amount of NPs that were irreversibly immobilized in 1 ml of GB slurry was determined to be ~30 mg using fluorescent-labeled NPs. Images obtained via scanning electron microscopy established that the NPs were uniformly immobilized on the surface of the pores without blocking the macropores. The model target protein (IgG) was reversibly captured by the NP-immobilized GBs through NP–IgG interactions. NP-immobilized GBs have potential applications as novel affinity purification media for proteins, combining inexpensive and stable ligands with high-performance supports. Nanogel particles (NP) that bind with the Fc fragment of immunoglobulin G (IgG) were immobilized on the pore surface of macroporous hard gel beads (GB) containing quaternary ammonium cations on the surface via multipoint electrostatic interactions. The model target protein (IgG) was reversibly captured by the NP-immobilized GBs through NP–IgG interactions. NP-immobilized GBs have potential applications as a novel affinity purification medium for proteins, combining an inexpensive and stable ligand with a high-performance support.

Magnetic Levitation as a Platform for Competitive Protein–Ligand Binding Assays

This paper describes a method based on magnetic levitation (MagLev) that is capable of indirectly measuring the binding of unlabeled ligands to unlabeled protein. We demonstrate this method by measuring the affinity of unlabeled bovine carbonic anhydrase (BCA) for a variety of ligands (most of which are benzene sulfonamide derivatives). This method utilizes porous gel beads that are functionalized with a common aryl sulfonamide ligand. The beads are incubated with BCA and allowed to reach an equilibrium state in which the majority of the immobilized ligands are bound to BCA. Since the beads are less dense than the protein, protein binding to the bead increases the overall density of the bead. This change in density can be monitored using MagLev. Transferring the beads to a solution containing no protein creates a situation where net protein efflux from the bead is thermodynamically favorable. The rate at which protein leaves the bead for the solution can be calculated from the rate at which the levitation height of the bead changes. If another small molecule ligand of BCA is dissolved in the solution, the rate of protein efflux is accelerated significantly. This paper develops a reaction-diffusion (RD) model to explain both this observation, and the physical-organic chemistry that underlies it. Using this model, we calculate the dissociation constants of several unlabeled ligands from BCA, using plots of levitation height versus time. Notably, although this method requires no electricity, and only a single piece of inexpensive equipment, it can measure accurately the binding of unlabeled proteins to small molecules over a wide range of dissociation constants (K(d) values within the range from ~10 nM to 100 μM are measured easily). Assays performed using this method generally can be completed within a relatively short time period (20 min-2 h). A deficiency of this system is that it is not, in its present form, applicable to proteins with molecular weight greater than approximately 65 kDa.

Retention behavior of very large biomolecules in ion-exchange chromatography

Hepatitis B virus surface antigen (HBsAg) particles were efficiently adsorbed (retained) on a Sulfate–cellulose (S–C) bead column, and then desorbed with sodium chloride solutions (0.5–3.0 M). The HBsAg particles were not efficiently retained onto either sulfopropyl–agarose (SP–A) or quaternary amine–agarose (Q–A) at pH 4.5, 6 and 8. The size-exclusion curve showed that proteins of molecular mass higher than ca. 20 000 cannot penetrate into the pores of S–C beads. The dynamic binding capacity (DBC) values of lysozyme (ca. 7 mg/ml-gel) and of γ-globulin (ca. 3 mg/ml gel) for S–C did not depend on the flow velocity while the DBC of γ-globulin for SP–A decreased sharply with an increase in flow velocity. These results indicated that very large molecules are adsorbed only onto the surface of S–C, which resulted in fast adsorption–desorption rates although the equilibrium adsorption capacity is lower than conventional porous gel beads. Because of the rapid adsorption rate, the DBC values of γ-globulin for S–C at high flow-rate regions are similar to those for SP–A. Bovine serum albumin was not adsorbed onto S–C. As this can not be explained by a simple electrostatic interaction mechanism, molecular recognition of S–C might be different from the agarose-based ion-exchange beads.

A review of gel permeation chromatography: Part I

Until comparatively recently, in the practice of gel permeation chromatography it has been customary to use porous gel beads that have an average diameter in the range between 75 and 100 microns, and which are packed into columns up to 4ft long and having an inside diameter of approximately 0.3in, in order to achieve a separation. A working pressure in the region of 40 psi is normal for each of these columns when eluted with solvents such as toluene or tetrahydrofuran (THF) at ambient temperature. Therefore, a pump that is capable of producing a steady pulseless flow at around 300 psi is sufficient to meet the working requirements of a combination of up to seven such GPC columns. At the customary flow rate of 1cm3 min‐1 a chromatograph equipped as described would produce a GPC scan of whole polymer in about 3 hours.