Study of amino ligands fixation to macroporous supports and their influence on albumin adsorption

Heterogeneous networks of ethylene glycol dimethacrylate and 2‐hydroxyethyl methacrylate [poly(EGDMA‐co‐HEMA)] were synthesized by suspension polymerization using different EGDMA contents and agitation speeds. The networks were actived with epichlorhydrine (Ech) or 1,4‐butanediol diglycidyl ether (BDGE), and then hexamethylenediamine (HMDA) or ethylenediamine (EDA) were conjugated to the support by coupling reaction. Here, a higher alkyldiamine concentration and temperature, and a longer reaction time led to higher yields. Amino ligands of the support III were used to analyze their adsorption performance of bovine serum albumin (BSA) from the adsorption kinetic. A more external location of HMDA amino ligands into network led to get the maximum adsorption in a time shorter than that with EDA. Due to its bigger size, the HMDA molecule was attached mostly to the network surface between larger pores, which favored a faster protein adsorption. When derivatives containing BDGE were compared, the EDA ligand displayed a BSA retention higher than that with HMDA, because a shorter separation between the ammonium groups along the spacer arm yielded a stronger electrostatic attraction on the protein. Clearly, the balance obtained between the pores system and the reagents molecular structure used in the formation of Ech‐HMDA generated the most efficient BSA adsorption. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009     

Accounting for the size of molecules in determination of adsorption isotherms by XPS; exemplified by adsorption of chicken egg albumin on titanium

The adsorption of chicken egg albumin on commercially pure titanium has been studied as a function of protein concentration, using X‐ray photoelectron spectroscopy (XPS). The adsorption isotherm has been plotted using the increase in N 1s intensity and also by measurement in the decrease in the Ti 2p intensity as the adsorbed film reaches full coverage. It is shown that both sets of data are a good fit to the Temkin isotherm. The influence of the large size of the biomolecule is discussed and the isotherm is modified to take account of the molecular dimension according to the model proposed by Ratner and Paynter. The thicknesses of the adsorbed molecules are measured using atomic force microscopy (AFM) and it is shown that it is only when monolayer coverage has been reached that the molecules begin to take up the characteristic globular shape. Albumin reaches a coverage of 25% of a monolayer in solutions of only 10 ppb by volume, suggesting that it is easily bound to the TiO₂ surface. A complete monolayer is formed at a solution concentration of 100 ppm. The carbon 1s signal is used to estimate the surface free energy at different surface coverages using the model developed by Kinloch, Kodokian and Watts. The transformation from the initial coverage of hydrophobic contamination molecules to the hydrophilic surface presented by the adsorbed albumin film takes place over a range similar to that required to form the monolayer. Copyright © 2005 John Wiley & Sons, Ltd.     

Influence of albumin adsorption on physico-chemical properties of alumina surfaces

The effect of albumin adsorption on neutral active aluminium oxide was investigated in the presence of polar and non-polar liquids. The adsorbed values were highest near the isoelectric point of albumin and varied in the range 5–10 and 3–11 mg g^–1 with phosphate buffer and potassium chloride respectively after 2 and 24 h. In the case of aluminium oxide the effect of albumin adsorption on total heterogeneity of adsorbents is not explicit. On the one hand, the modified samples showed decreasing surface area with increase of surface coverage with albumin. On the other hand, modifications under the same conditions but without albumin caused similar changes. These effects suggest the strong influence of medium pH on surface properties (due to surface polarization) and competitive co-adsorption of ions on the process. The volumetric fractal dimensions of the studied materials change in the range 2.25–2.32 for pure aluminium oxide and BSA modified from the phosphate solution. E _d,max values (desorption energy in the maximum of distribution function) diminish (in the range 40–45 kJ mol^–1) compared with pure aluminium oxide (E _d,max=52 kJ mol^–1) for water thermodesorption at modified surfaces to the increase of a number of active centers of hydrophobic character, and weakening of the adsorbent–adsorbate increases.     

Equilibrium Swelling of an Epoxy‐Resin in Contact with Water – A Molecular Dynamics Simulation Study

Full Paper: We have studied the equilibrium swelling of an idealized model network based on a realistic epoxy‐resin in contact with water using the molecular dynamics simulation method. We use a novel method to measure the water chemical potential inside the network as function of water concentration. The equality of the water chemical potential computed in this fashion with the bulk water chemical potential under the same thermodynamic conditions determines the equilibrium water content and the swelling ratio. We study the dependence of the water content as function of temperature and as function of the size of the atomic partial charges.

Schematic representation of the simulation volume. Spheres represent epoxy units with n = 0. The dashed lines represent curing agent units with m = 5.     

Dynamics of Polymer Networks with Strong Differences in the Viscous Characteristics of their Crosslinks and Strands

We study theoretically the relaxation properties of polymer networks, whose monomers and junction sites have different friction parameters (ζ and ζ_jun, respectively). For this, we focus on topologically regular cubic networks built from “bead‐and‐spring” Rouse chains. Setting σ = ζ_jun/ζ, we determine analytically both the eigenvalues and the eigenmodes of the model for arbitrary values of σ. This allows us to extend previous approaches (Macromolecules 2000 , 33, 6578) which were restricted by the condition σ = 3. We compute the frequency dependent storage, G′(ω), and loss, G″(ω), moduli (which for σ ≫ 3 or σ ≪ 3 display two plateaus and two maxima, respectively) and also the mean‐square displacements of the network junctions and of the beads; these turn out to obey power laws, whose validity ranges depend on σ.

     

Flexibility transitions and looped adsorption of wormlike chains

When deposited from a solution onto a surface, superpolymeric chains display revealing transitions in their apparent stiffness. With simulated chains in adsorption, we varied the backbone rigidity and measured the chain persistence length (l_Pads). As the three‐dimensional persistence length (l_P3) increases toward the contour length, a transition can be seen from l_Pads = l_P2 (i.e., the two‐dimensional persistence length) to l_Pads = l_P3. Looped conformations decrease in frequency with a distinct nonlinear dependence. Finally, comparisons with experiments on polymeric worm micelles and purified neurofilaments demonstrate a simple new method for assessing the flexibility of these novel superpolymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 280–286, 2005     

Effect of surface charge on adsorption of bovine serum albumin as studied by ellipsometry 1. Adsorption on cationic monolayer

The adsorption of bovine serum albumin (BSA) onto a cationic monolayer (N,N-dimethyl-N,N-dialkylammonium chloride) spread at the air/water interface was studied by ellipsometry. Both thicknesses and refractive indices of the BSA layer adsorbed at the monolayer/solution interface are estimated from the observed change in phase difference and the ratio of reflection coefficients. The amount of adsorption of BSA resembles a Langmuir type isotherm. The adsorption changes with pH asymmetrically with respect to the pH of maximum adsorption, which was calculated to be 5.06 ± 0.47 mg/m². The amount of maximum adsorption implies that the BSA molecule adsorbs to the surface in a mode intermediate between side-on and end-on.     

Synthesis of Cationic and Ampholytic Starch Graft Acrylamide and their Aqueous Salt Absorption

Acrylamide was grafted onto starch using ceric(IV) ion as initiator. Starch–graft-polyacrylamide was then modified through Mannich reaction using formaldehyde and diethylamine to give poly(N, N′-[(diethylamino) methyl]-acrylamide). The modified-graft copolymer was quaternized using different reagents; methyl iodide, n-butylbromide, sodium chloroacetate and propane sultone to give cationic and ampholytic graft materials. The absorbing properties of the produced materials toward deionized water and aqueous salt solutions were investigated. Studies of the absorbing properties of polyampholytes have revealed that these materials do not shrink upon increasing salt concentration. Kinetics of swelling in deionized water is also discussed.     

In situ monitoring of gold-surface adsorption and acidic denaturation of human serum albumin by an isolation-capacitance-adopted electrochemical quartz crystal impedance system

Combined measurements of piezoelectric quartz crystal impedance (PQCI) and electrochemical impedance spectrum (EIS) using a suitable isolation capacitance is reported for the first time to monitor in situ adsorption and acidic denaturation of human serum albumin (HSA) on gold electrodes in Britton-Robinson (B-R) buffers. This method provides simultaneously mutual-interference-free and accurate parameters of EIS and PQCI. Effects of surface thiol-modification, electrode-potential and solution pH on HSA adsorption were examined and discussed. Comparative experiments of HSA adsorption in a B-R buffer of pH 6.42 on bare, cysteine- and 1-dodecanethiol-modified gold electrodes revealed that HSA adsorption is more significant on a hydrophobic (1-dodecanethiol-modified) surface. Insignificant electrode-potential effect implied minor electrostatic effects on HSA adsorption. The adsorption amount of HSA at pH 3.28 was found to be notably greater than those at pH 4.84 and 6.42. To characterize HSA adsorption, electrode standard rate constants (k_s) of the Fe(CN)₆³⁻/Fe(CN)₆⁴⁻ couple were measured before and after HSA adsorption. The k_s-pH curves on an HSA-modified Au electrode revealed that k_s increased abruptly with the decrease of solution pH below pH ∼4. Moreover, pH-dependent responses of the resonant frequency, the motional resistance, the double-layer capacitance, the capacitance of adsorbed HSA layer and the peak absorbance of HSA solutions at 278 nm all exhibited an inflexion change at pH ∼4, and these findings have been explained on the basis of acidic denaturation of HSA and electrical charges carried by HSA molecules.     

A study of adsorption behavior of human serum albumin and ovalbumin on hydroxyapatite/chitosan composite

In situ adsorption of human serum albumin (HSA) and ovalbumin (OVA) was real-time monitored by piezoelectric quartz crystal impedance (PQCI) technique to fully understand the initial cellular response on hydroxyapatite/chitosan (HAP/CS) composite. The PQCI parameters, such as resonant frequency (f), static capacitance (C_s), and motional resistance (R_m) were measured for investigating the kinetic adsorption behaviors of both proteins. The change in frequency shifts (Δf) depends on the amount of the adsorbed protein, and the change in motional resistance (ΔR_m) results from the microporosity variation of HAP/CS coating. The results show that the amount of the absorbed HSA is much greater than that of OVA on HAP/CS coating because of the unique construction of HSA as well as a flexible protein. Furthermore, Δf and ΔR_m data were fitted according to the kinetic exponential decay equations. It can be seen that there is only one adsorption process for OVA, but the absorption process for HSA is followed by a rearrangement process, and the former process is faster than the rearrangement process. Subsequently, the composite binding with proteins were demonstrated by the Fourier transform infrared (FTIR), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS).     

Competitive adsorption of fibrinogen and albumin onto polymer microspheres having hydrophilic/hydrophobic heterogeneous surface structures

The competitive adsorption of bovine fibrinogen (BFb) and bovine serum albumin onto polymer microspheres from the mixture solution was examined under various protein-to-microsphere ratios using various homopolymer microspheres and poly(2-hydroxyethyl methacrylate)/polystyrene composite microspheres having heterogeneous surface structures consisting of both hydrophilic and hydrophobic parts. They were produced by emulsifier-free (seeded) emulsion polymerizations. The selective adsorption of BFb was not observed for the homopolymer microspheres, but observed for the composite polymer microspheres having optimum compositions.Part CXXXVIII on the series Studies on Suspension and Emulsion     

Synthesis of macroporous polymer rods based on an acrylamide derivative monomer

New macroporous polymer rods were prepared by free‐radical crosslinking copolymerization from N‐acryloyl‐tris(hydroxymethyl)aminomethane and N,N′‐methylenebisacrylamide as a crosslinking agent with different porogenic mixtures and with azobisisobutyronitrile as an initiator. The porous properties of these materials were controlled through changes in the proportions of the porogenic mixture, the polymerization temperature, or the concentration of the crosslinking agent. Pore size distribution profiles that shifted toward a larger pore size were obtained in the following cases: when the percentage of the coporogen was increased, when the copolymerization reactions were carried out at a low temperature (55 °C), and when the crosslinking concentration was reduced. Alternatively, a porogenic mixture formed from dimethyl sulfoxide and a 1:1 combination of tetradecanol and poly(ethylene glycol) 6000 as coporogens yielded a polymer rod with a high porosity and pore size. These hydrophilic materials are promising as base supports for different chromatographic processes and as throughput bioreactors. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6616–6623, 2006     

Synthesis of thiol chelating resins and their adsorption properties toward heavy metal ions

A series of chelating resins, derived from a macroreticular styrene-divinylbenzene (2%) copolymer beads grafted with various poly(ethylene glycols) HO? (? CH₂? CH₂? O? )_n? H(n = 0, 4, 9, 13) and containing thiol groups as chelating functions, have been synthesized in a three-step reaction sequence. The structure of the functionalized resins was confirmed by IR spectrophotometry, elemental analysis, and differential scanning calorimetry. The complexation behavior of these thiol resins was investigated towards Hg(II), Cu(II), and Pb(II) ions in aqueous solution by a batch equilibration technique. The influence of pH on adsorption capacity was also examined. The adsorption values for metal ions' intake followed the order Hg(II) > Cu(II) > Pb(II). The affinity of these polymers towards Hg(II) ions was so high that the total mercury level in the liquid decreased from 20 ppm to below 10 ppb after 2 h of treatment. Polymers can be regenerated by washing with a solution of hydrochloric acid (6N) and 10% by weight of an aqueous solution of thiourea. © 1994 John Wiley & Sons, Inc.     

Synthesis of stimuli‐responsive macroazoinitiators and their use as an inistab toward hairy polymer latex particles

Stimuli‐responsive macroazoinitiators with central azo unit have been synthesized by atom transfer radical polymerization (ATRP) of 2‐(dimethylamino)ethyl methacrylate or 2‐(diethylamino)ethyl methacrylate in 2‐propanol at 25 °C. The mean degree of polymerization of the polymer chains besides the azo group was fixed between 25 and 60. ¹H NMR, gel permeation chromatography, UV‐Vis spectrophotometer, and surface tensiometer were used to characterize the stimuli‐responsive macroazoinitiators in terms of their chemical structure, molecular weight, polydispersity, and pH‐responsive behavior, respectively. Eventually, dispersion polymerization of styrene using the poly[2‐(diethylamino)ethyl methacrylate] (PDEA) macroazoinitiator as an inistab (initiator + stabilizer) in 2‐propanol medium was conducted. Near‐monodisperse 98 nm polystyrene (PS) latex particles with pH‐responsive PDEA hair were successfully synthesized. The PS latex particles with the PDEA hair can be dispersed in acidic aqueous media where the PDEA hair was protonated and was solvated, and can be flocculated in basic aqueous media where the PDEA hair was deprotonated and was precipitated. This dispersion‐flocculation cycle was reversible. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3431–3443, 2009     

Synthesis and interaction studies of benzimidazole derivative with human serum albumin

A benzimidazole derivative, 1-(2-picolyl)-3-(2-picolyl) benzimidazole iodide (PPB), was synthesized. Fourier transform infrared spectroscopy (FT-IR), UV–visible, three-dimensional (3D) fluorescence, synchronous fluorescence (SF) and fluorescence spectroscopic methods were used to determine the PPB binding mode and the effects of PPB on protein stability and secondary structure. Fluorescence results revealed the presence of static type of quenching mechanism in the binding of PPB to human serum albumin (HSA). The binding constants between PPB and HSA were obtained according to Scatchard equation. The number of binding sites, the binding constants and the thermodynamic parameters were measured. The results showed a spontaneous binding of PPB to HSA through hydrogen bonds and van der Waals forces. In addition, the distance between PPB and the Trp 214 was estimated via employing the Förster's non-radiative energy transfer theory, and was found to be 3.49 nm, which indicated that PPB can bind to HSA with high probability. Site marker competitive experiments indicated that the binding of PPB to HSA primarily took place in subdomain IIA.     

Role played by the head size of some non‐ionic surfactants on their adsorption onto montmorillonite clay

Sorption behavior of polyoxethylene(n)monooleate series [Ol(EO)_n] onto montmorillonite clay was studied at 25°C to investigate the influence of the surfactant's head size on the sorption process. All the tested surfactants exhibited L‐shaped isotherms that means a strong interaction between the adsorbent and the adsorbate. Also, all the obtained isotherms ended with a drastic increase in the isotherm slope at nearly constant equilibrium concentration. This abrupt increase reflected the fairly high affinity of the tested surfactants to the clay surface at high bulk concentration region. The maximum amount adsorbed at the plateau region, Γ_max, was calculated according to the Langmuir adsorption theory and followed the order: Ol(EO)₁₄ > Ol(EO)₂₀ < Ol(EO)₄₀ < Ol(EO)₈₀. In case of short ethylene oxide (EO) chain, Γ_max decreased with the increase in the chain length; but a reverse result was obtained in case of surfactants with longer EO chain length (20 to 80 units). The free energy of adsorption, ΔG°_ad, had negative values indicating the spontaneous adsorption of surfactant molecules onto clay. The values of ΔG°_ad increased with increasing EO units from 14 to 20 units and decreased with further elongation in the EO chain from 20 to 80 units. Copyright © 2004 John Wiley & Sons, Ltd.     

Synthesis and characterization of new polydiolcitrates with tunable properties

Polydiolcitrates are an emerging class of biocompatible polyesters with a great potential in the field of biomedicine and packaging for food and drug materials. In this work, a new type of (co‐)polydiolcitrates made of citric acid (CA) and ethylene glycol (EG) and/or poly(ethylene glycol) (PEG) is investigated. By varying both the EG/PEG and the CA/diol molar ratios, materials exhibiting very different swelling behavior, mechanical and thermal properties are obtained. In particular, the substitution of EG segments with longer and flexible PEG ones results in an increase in crosslinking density, with remarkable effects on swelling capacity, glass transition temperature, and Young modulus. Moreover, polyesters with CA/diol molar ratio equal to 1:1 exhibit shape memory properties, with full capacity of keeping the temporary shape and high capacity of recovering the original shape. This work demonstrates that the appropriate choice of polyester composition allows modulating the sample properties, that permits to these materials to cover a wide range of possible applications. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3713–3720     

Synthesis of hydrophilic sorbents from N‐vinylimidazole/divinylbenzene and the evaluation of their sorption properties in the solid‐phase extraction of polar compounds

This article reports the synthesis of N‐vinylimidazole/divinylbenzene resins by suspension polymerization. Several polymerization conditions were tested to achieve a quantitative incorporation of the N‐vinylimidazole monomer into the final polymer while a high specific surface area was maintained. The retention properties of several copolymers with different nitrogen contents were evaluated with the solid‐phase extraction of polar compounds from water samples, and the best results were obtained for a polymer containing 6.3% N with a surface area of 627 m² g^?1. The sorption properties of the resins were compared to those of styrene–divinylbenzene and other copolymers containing nitrogen, and the results were best for the new sorbents with N‐vinylimidazole as the polar monomer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2019–2025, 2004     

PS-TEPA树脂合成及其吸附蛋白质性质

本文以四乙烯五胺与氯乙酰化聚苯乙烯树脂反应合成PS-TEPA树脂。考察了温度、时间、胺用量以及溶剂等合成条件。研究了PS-TEPA树脂吸附牛血清蛋白的条件,包括吸附温度、吸附时间以及蛋白质的用量。结果发现,当以二氯甲烷作分散剂,合成温度为85℃,反应时间为12 h,投料比为32g四乙烯五胺/g树脂条件下,树脂接枝的增重率和氮元素含量最大;当吸附温度为30℃,吸附时间为12 h,牛血清蛋白溶液的浓度为2.0 mg/mL时,PS-TEPA树脂的蛋白吸附量达到80mg/g树脂,吸附回收率为84%。