Adsorption and viscoelastic properties of fractionated mucin (BSM) and bovine serum albumin (BSA) studied with quartz crystal microbalance (QCM-D)

The adsorption profile and viscoelastic properties of bovine submaxillary gland mucin (BSM) and bovine serum albumin (BSA), extracted from a commercial mucin preparation, adsorbing to polystyrene surfaces has been studied using quartz crystal microbalance with dissipation monitoring (QCM-D). A significant difference in the adsorption properties of the different proteins was detected; with the BSA adsorbing in a flat rigid layer whilst the mucin adsorbed in a diffuse, highly viscoelastic layer. Subsequent addition of BSA to the preadsorbed mucin layer resulted in stiffening of the protein layer which was attributed to complexation of the mucin by BSA. In contrast, a preadsorbed layer of BSA prevented mucin adsorption altogether. Combined mixtures of mucin and BSA in well defined ratios revealed intermediate properties between the two separate protein species which varied systematically with the protein ratios. The results shed light on the synergistic effects of complexation of lower molecular weight biomolecular species with mucin. The possibility to selectively control protein uptake and tailor the physical properties of the adsorbed layer makes mucin an attractive option for application in biomaterial coatings.     

Mucin coating on polymeric material surfaces to suppress bacterial adhesion

Mucin, a group of large glycoproteins, constitutes one of the major components of mucous which covers the lumenal surfaces of epithelial organs and serves as a physical barrier between the extracellular milieu and the plasma membrane. The molecules have a generic structure consisting of a thread-like peptide backbone with densely packed carbohydrate side chains. Protein and carbohydrate contents are about 30 and 50%, respectively. On hydrophobic materials in aqueous environments the naked parts of mucin’s protein backbone will adhere due to their hydrophobicity, while the carbohydrate side chains are thought to orient themselves away from the surface. This gives the mucin molecules their unique properties as surfactants, i.e. they tend to adsorb to hydrophobic surfaces via protein-surface interactions while they hold water molecules via their hydrophilic oligosaccharide clusters. In the present work, bovine submaxillary gland mucin (BSM) is purified by SEC and subsequently characterized with PAGE. Four polymeric materials, PMMA, silicone, Tecoflex® polyurethane and polystyrene, are selected as coating targets. Contact angle measurements show significant changes in these materials after coating with BSM. Surface concentrations of adsorbed BSM are determined by amino acid analysis and found to correlate well with observed reductions in contact angle. Both Staphylococcus aureus and CNS S. epidermidis are used to contaminate uncoated and BSM coated surfaces of all four materials, demonstrating a correlation between suppression of bacterial adhesion and surface concentration of BSM. Thus, bacterial counts on the coated PMMA, PS, PU and silicone specimens amount to ≈3, 10, 8 and 30% of the counts found on their uncoated counterparts. These results suggest that mucin coatings could profitably be employed to reduce the risk of microbial infections on polymeric biomaterials.     

Interactions of β-Lactoglobulin with Bovine Submaxillary Mucin vs. Porcine Gastric Mucin: The Role of Hydrophobic and Hydrophilic Residues as Studied by Fluorescence Spectroscopy

The aim of this study was to investigate binding interactions between β-lactoglobulin (BLG) and two different mucins, bovine submaxillary mucins (BSM) and porcine gastric mucin (PGM), using intrinsic and extrinsic fluorescence spectroscopies. Intrinsic fluorescence spectra showed an enhanced decrease of fluorescence intensity of BLG at all pH conditions when BLG was mixed with PGM rather than with BSM. We propose that, unlike BSM, the tertiary structure of PGM changes and the hydrophobic regions are exposed at pH 3 due to protonation of negatively charged residues. Results suggest that PGM also facilitated the structural unfolding of BLG and its binding with PGM by a hydrophobic interaction, especially at acidic pH, which was further supported by extrinsic fluorescence spectroscopy. Hydrophobic interaction is suggested as the dominant interaction mechanism between BLG and PGM at pH 3, whereas electrostatic interaction is the dominant one between BLG and BSM.     

Effects of mucin addition on the stability of oil–water emulsions

In this work, bovine submaxillary gland mucin (BSM) was used as an emulsifier to stabilize oil–water emulsion systems. Prior to use, commercial BSM was purified by jacalin affinity chromatography. Emulsions consisting of 5% mineral oil in phosphate buffered saline (PBS) were prepared through the addition of different amounts of purified mucin followed by sonication using either of two methods: (1) low energy input for a long time (2 h), or (2) high energy input for a short time (20 s). The surfactancy property of mucin was investigated by surface tension measurements, which showed the BSM to greatly reduce the surface tension of PBS. Compared to several synthetic surfactants of the Pluronic® type, mucin showed comparable or better surface activity than F68, F88 and F108 products in dilute solutions. The formed emulsions had a mean droplet size that decreased monotonically with increasing concentration of mucin until a plateau was reached at concentrations around 0.1% by weight. The stability of these emulsions was evaluated by monitoring their average droplet size during a 33-day period. Emulsions with more than 0.25% mucin showed a constant mean size throughout the period. Specifically, an emulsion produced with 0.95% mucin showed a stable mean droplet size of about 300 nm. The stability of the mucin-emulsified systems was also evaluated by measuring turbidity changes with time, which allowed a comparison with similar emulsions stabilized by the Pluronic® surfactants in the same concentration. Thus, mucin showed its ability to establish more stable and more efficient oil–water emulsion systems. Since mucin is a glycoprotein, and hence biodegradable, our results suggest that mucin might serve as an ideal biological surfactant for the stabilization of emulsion systems intended for biomedical and pharmaceutical applications.     

聚(N-对乙烯基苄基二甲胺)树脂对苯酚的吸附性能

采用二甲胺为功能化试剂,化学修饰氯甲基化苯乙烯-二乙烯基苯共聚物合成了大孔交联聚(N-对乙烯基苄基二甲胺)树脂,测得树脂的氯含量由4.2mmol/g降低到0.24mmol/g,树脂的弱碱交换量为4.0mmol/g,说明氯甲基化苯乙烯-二乙烯基苯共聚物发生胺化反应完全。在水溶液中,测定了大孔交联聚(N-对乙烯基苄基二甲胺)树脂对苯酚的吸附等温线,发现吸附平衡数据符合Freundlich等温吸附方程,相关系数大于0.99。计算得到在吸附量为15、20和25mg/g时,等量吸附焓在-20.81~-30.74kJ/mol范围内,吸附自由能和吸附熵均小于0,说明吸附过程中存在氢键作用,吸附是自发、混乱度变小的过程。比较树脂对水溶液中苯酚、对硝基苯酚和对硝基甲苯的吸附性能以及树脂对水、环己烷、乙醇和乙酸乙酯溶液中苯酚的吸附性能,进一步说明大孔交联聚(N-对乙烯基苄基二甲胺)树脂对水溶液中苯酚的吸附是基于疏水作用和氢键作用协同的机理。     

Adsorption-desorption isotherm hysteresis of beta-lactoglobulin A with a weakly hydrophobic surface.

Adsorption-desorption isotherms of bovine beta-lactoglobulin A (beta-lact A) on a weakly hydrophobic stationary phase (C1-ether) were measured by frontal analysis. The adsorption isotherms obtained at different pH were found to be dramatically different in shape, column capacity and desorption reversibility. At pH 4.5, an S-shaped adsorption isotherm was observed whereas at pH 6.0 a Langmuir isotherm was found. In addition, the desorption isotherm at pH 6.0 was found to overlap with the adsorption isotherm, and the adsorption-desorption process of beta-lact A under this condition could be characterized by a fully reversible Langmuir model. The desorption isotherm at pH 4.5, however, did not retrace the adsorption isotherm, resulting in hysteresis loops. A higher aggregate (tetramer) of beta-lact A is shown to be in an equilibrium with the beta-lact A protomer (dimer) at pH 4.5 whereas the dimer alone is predominant at pH 6.0. It is further shown that changes in the absorption coefficient between the adsorption and the desorption cycles for the tetramer at pH 4.5 can account for the hysteresis. The results demonstrate that pH can be a sensitive parameter in protein adsorption isotherm behavior and ultimately the behavior of species in preparative-scale chromatography.     

Experimental Approaches to Adsorption-Desorption Dynamism of Human Serum Albumin (HSA) onto Crosslinked N,N′-Diethylaminoethyl (DEAE) Dextran Microbeads

Crosslinked N,N′-Diethylaminoethyl (DEAE) groups containing dextran microbeads have been used in human serum albumin (HSA) adsorption-desorption studies. For the HSA adsorption onto positively charged hydrophilic DEAE dextran microbeads, the adsorption kinetic was slightly decreased by the changing concentration of the protein solution. Adsorption kinetics and equilibrium isotherms for the adsorption of HSA on crosslinked DEAE dextran have been determined experimentally. Modeling of the adsorption processes on DEAE dextran microbeads were realized by applying different adsorption isotherms. Among the several isotherm equations, Langmuir and Freundlich adsorption isotherms were investigated depending on the two temperatures. These were only slightly dependent on the initial concentration of HSA but were considerably affected by the pH of the medium. The HSA adsorption capacity factor and the adsorption equilibrium constant were obtained and mathematical modeling of adsorption, adsorption rate constants and maximum adsorption were determined. Besides the adsorption mechanism, optimum ionic strength and optimum pH also were investigated. Desorption studies and desorption ratio of the system were determined for optimum medium conditions. It was been proved both experimentally and theoretically that human HSA is adsorbed by electrostatic attraction, ion-exchange, hydrophobic interaction and/or hydrogen bonding.     

Preliminary assessment of the modification of polystyrene‐divinylbenzene resin with lipid‐tethered ligands for selective separations

Functionalized lipid tethered ligands use physical adsorption to anchor reactive head groups to hydrophobic supports. We previously demonstrated the use of these species adsorbed onto polypropylene capillary‐channeled polymer fibers. The general use of lipid tethered ligands on other hydrophobic chromatographic supports is demonstrated here for polystyrene‐divinylbenzene. Evaluation of ligand adsorption conditions was performed using a fluorescein isocyanate head group to quantify the extent of loading by UV‐Vis absorbance and by fluorescence microscopy. Selective protein capture was demonstrated by the detection of Texas Red labeled streptavidin (using fluorescence microscopy imaging, with quantification assessed through the depletion of solution‐phase protein using UV‐Vis absorbance. A second demonstration of the coupling involved an iminodiacetic acid head group lipid tethered ligand to capture the cationic dye, methylene blue. Two common means of alleviating nonspecific binding, adsorption in detergent media and use of a bovine serum albumin block, were evaluated. The first was found to cause release of the ligands, while the second was nominally effective. Indeed, the lipid tethered ligands itself may be most effective at impeding nonspecific binding. While further optimization and chromatographic evaluation is required, the general viability of this ligand immobilization method onto this common polymer support is demonstrated.     

ZrO2负载碳纳米管吸附去除水中氟的研究

以ZrO2负载多壁碳纳米管(ZrO2-MWCT)为吸附剂,系统研究了其对水中F-的吸附、脱附性能。结果表明,F-在ZrO2-MWCT吸附剂上的吸附等温线可以用Freundlich方程模拟,吸附动力学符合拟二级动力学方程,吸附速率随着F-初始浓度的提高而减低。当pH为4~5时,F-在ZrO2-MWCT吸附剂上的吸附量最大。水中阴离子的存在降低ZrO2-MWCT对F-的吸附量,不同阴离子对F-影响的大小顺序为:CO32->SO42->Cl->NO3-。吸附饱和的ZrO2-MWCT可用0.1mol/L的NaOH脱附再生,经4次再生后,其吸附量仍为14.55mg/g。     

Adsorption of polyethylene glycol (PEG) from aqueous solution onto hydrophobic zeolite

In the present study, a hydrophobic zeolite was used as an adsorbent for the adsorption of polyethylene glycol (PEG) in water solution and electroplating solution at 25 degrees C. The adsorption capacities were determined through the adsorption isotherms in a thermostated shaker. The rate of adsorption, on the other hand, was investigated in a batch adsorber under controlled process parameters such as initial PEG concentration (30, 70, 110, 150, 200, and 300 mg x dm(-3)), agitation speed (200, 800, and 1000 rpm), and adsorbent particle size (0.72, 1.44, and 2.03 mm). A batch kinetic model, according to a pseudo-second-order mechanism, has been tested to predict the rate constant of adsorption, equilibrium adsorption capacity, time of half-adsorption, and equilibrium concentration by the fitting of the experimental data. The results of the adsorption isotherm and kinetic studies show that the adsorption process can well be described with the Langmuir and Freundlich models and the pseudo-second-order equation, respectively. Comparing the values of adsorption parameters of PEG in water solution and electroplating solution, there are no significant differences. In addition, the effective diffusion coefficient of the PEG molecule in the microporous adsorbent has been estimated at about 3.20 x 10(-8) cm(2)s(-1) based on the restrictive diffusion model.     

玻璃硅烷化处理对罗丹明6G和亚甲基蓝吸附行为的影响

利用六甲基二硅烷胺对平面玻璃光波导(高折射率透明导光薄膜介质)进行硅烷化处理, 得到水接触角大于90°的疏水表面. 然后使用时间分辨光波导分光光谱技术研究水溶液中的罗丹明6G (R6G)和亚甲基蓝(MB)分子在疏水玻璃表面的吸附行为, 并与亲水玻璃条件下测得的结果进行对比. 对利用疏水玻璃光波导测得的R6G的吸附-脱附动力学曲线进行Langmuir拟合得到了R6G的吸附速率常数, 脱附速率常数以及吸附自由能. 并且发现与亲水玻璃情况相比, 吸附速率常数增大, 脱附速率常数减小, 吸附自由能更负. 在疏水玻璃表面形成的R6G和MB吸附层的吸光度与亲水玻璃情况相比显著升高, 表明这两种分子更倾向于吸附在疏水玻璃表面. 实验结果还发现玻璃硅烷化处理能够有效抑制这两种染料分子在表面的聚合反应.     

大孔交联聚(对乙烯基苄基苯基醚)树脂对苯酚的吸附机理

由氯甲基化聚苯乙烯合成了大孔交联聚(对乙烯基苄基苯基醚)树脂(简称为苯基醚树脂), 测定了其对正己烷和水中苯酚的吸附等温线, 计算了吸附焓. 同时, 比较了聚(对乙烯基苄甲醚)、苯基醚树脂、聚(对乙烯基苄基对硝基苯基醚)和聚(对乙烯基苄基对甲基苯基醚)对正己烷中苯酚的吸附性能以及氯甲基化聚苯乙烯和苯基醚树脂对水中苯酚、2,3,5-三甲基苯酚和对硝基甲苯的吸附性能. 结果表明, 苯基醚树脂是通过氢键吸附正己烷溶液中苯酚的, 而其对水中苯酚的吸附是基于氢键和疏水作用的协同.     

Synthesis of the water-compatible p-acetaminophen resin and its adsorption performances for vanillin in aqueous solution

A novel p-acetaminophen resin(named as GQ-1) was synthesized with chloromethylated polystyrene and p-acetaminophen.It can be used without any wetting process.The objective of this work was to study the adsorption performances for vanillin onto GQ-1 with two kinds of the hydrogen bond site of acetamino group and hydroxyl group.The results showed that the adsorption property of vanillin onto GQ-1 was superior to XAD-4,H103,NDA150,and NDA88.The adsorption capacity of vanillin onto GQ-1 is not greatly discrepant until the solution pH is higher than 5.31.The saturated adsorption quantity of vanillin was up to 141.32 mg/mL(wet resin) according to the dynamic adsorption and desorption experiments at 293 K.The resin could be regenerated by 7 BV ethanol.     

Preferential adsorption of bovine serum albumin dimer onto polymer microspheres having a heterogeneous surface consisting of hydrophobic and hydrophilic parts

The adsorption behaviors of bovine serum albumin (BSA) containing both dimeric and monomeric species onto polymer microspheres were examined using various homopolymers and poly(2-hydroxyethyl methacrylate)/polystyrene composite microspheres which were produced by the emulsifier-free (seeded) emulsion polymerization technique. The preferential adsorption of the BSA dimer was clearly observed in an optimum region of the surface hydrophilicities of the polymer microspheres. The preferential adsorption of the BSA dimer onto the composite polymer microspheres having heterogeneous surfaces consisting of hydrophilic and hydrophobic parts was more marked than those onto the homopolymer and copolymer microspheres having homogeneous surfaces.     

Protein interactions with model chromatographic stationary phases constructed using self-assembled monolayers

Model surfaces representative of chromatographic stationary phases were developed by immobilising an homologous series (C2-C18) of n-alkylthiols, mixed monolayers of C4/C18 and thioalkanes with alcohol, carboxylic acid, amino and sulphonic acid terminal groups onto a flat, silver-coated glass surface using self-assembled monolayer (SAM) chemistry. The processes of adsorption and desorption of serum albumins onto the monolayer surfaces was monitored in real-time using surface plasmon resonance (SPR). Alkyl-terminated SAMs all showed a strong adsorption of bovine serum albumin which was largely independent of alkyl chain length, the ratio of mixed C4/C18 SAMs or the solution pH/ionic strength. The adsorption of human serum albumin to carboxylic and amine terminated SAMs was shown to be predominantly via non-electrostatic interactions (hydrophobic or hydrogen bonding). However, sulphonic acid terminated SAMs showed almost exclusively electrostatic interactions with human serum albumin. This preliminary work using self-assembled monolayer chemistry confirms the usefulness of well characterised SAMs surfaces for investigating protein adsorption and desorption onto/from model chromatography surfaces and gives some guidance for selecting appropriate functionalities to develop better surfaces for chromatography and electrophoresis.     

Interaction of 2-chloronaphthalene with high carbon iron filings (HCIF): adsorption, dehalogenation and mass transfer limitations

Interaction of 2-chloronaphthalene (2-CN) with high-carbon iron filings (HCIF) was studied in anaerobic batch systems, both under well-mixed and poorly-mixed conditions. In well-mixed conditions, partitioning of 2-CN between solid and aqueous phases was fast, resulting in rapid attainment of equilibrium. Equilibrium partitioning could be described by a Freundlich isotherm, C(s)=K x [C(a)](m), where C(s) (micromoles g(-1) iron) and C(a) (micromoles L(-1)) were the solid and aqueous phase 2-CN concentrations, respectively. Isotherm parameters, m and K were determined to be 0.76 and 5.6 x 10(-2) (micromole g(-1) iron)/(micromole L(-1)), respectively. Sorption (k(2)) and desorption (k(3)) rate constants were determined to be 5.60 x 10(-1) h(-1) g(-1) iron L and 10 h(-1), respectively. Reductive dehalogenation of aqueous phase 2-CN occurred concurrently but at a slower rate, and could be described by the expression (dC(T)//dt)= -k(1) x M x (C(a))(N), where C(T) (micromoles L(-1)) was the total 2-CN concentration and M (g iron L(-1)) the concentration of HCIF. The values of k(1) and N were determined to be 1.09 x 10(-2) h(-1) g(-1) iron L and 1.647, respectively. In poorly mixed conditions, adsorption (k(2)) and desorption (k(3)) rate constants were 3.92 x 10(-5) h(-1) g(-1) iron L and 7 x 10(-4) h(-1), respectively, i.e., several orders of magnitude less than in well-mixed systems. The dehalogenation rate parameters, k(1) and N were determined to be 2.22 x 10(-4) h(-1) g(-1) iron L and 0.986, respectively, suggesting slower dehalogenation. These results highlight how mass-transfer limitations during the interaction between HCIF and 2-CN in poorly mixed systems, such as permeable reactive barriers (PRBs), can potentially impact the dehalogenation process.     

Rinse and evaporation coating of poly(methyl methacrylate) microchip for separation of sodium dodecyl sulfate-protein complex

We developed a novel channel wall coating on a poly(methyl methacrylate) (PMMA) microchip using methylcellulose (MC) as a coating reagent to suppress electroosmotic flow (EOF) following the strong analytes adsorption via hydrophobic interaction with channel walls of PMMA. Our coating was obtained by first rinsing channel walls with MC-containing aqueous solution followed by evaporation. The coating made the hydrophilic channel wall lowering EOF by two orders of magnitude (1.2 x 10(-5)cm(2)V(-1)s(-1)) as well as reducing the hydrophobic adsorption. On the coated channel walls, we successfully separated sodium dodecyl sulfate-protein complexes with high reproducibility and efficiency using dextran as a lower viscosity protein separation medium.     

Macroporous chitosan layer coated on non-porous silica gel as a support for metal chelate affinity chromatographic adsorbent

A new immobilized metal affinity chromatography (IMAC) matrix was prepared by coordinating Cu2+ with cross-linked chitosan coated on non-porous silica gel (Cu-CTS-SiO2). Macroporous structure could be formed on the coated layer by imprinting polyethylene glycol (PEG) in chitosan film. The surface morphology changes on Cu-CTS-SiO2 bead prepared in different condition were confirmed by scanning electron microscopy (SEM). Effects of chitosan and PEG content in coating solution, the molecular mass of PEG on the surface macropore formation and adsorption capacity of bovine serum albumin (BSA) were investigated. Results indicated that coating solution with 2% chitosan and 10% PEG 20000 was optimal. Batch experiments were also conducted for elucidating the optimal pH, the adsorption isotherm and adsorption kinetics of BSA. Adsorption isotherm of trypsin on the same adsorbent was also performed. Results showed that the support itself had low non-specific interaction with both BSA and trypsin. The maximum adsorption capacity for BSA and trypsin on the prepared IMAC adsorbent could reach 192 mg and 5000 IU, respectively calculated by every gram of chitosan. The binding and eluting condition for BSA were tested on column filled with the adsorbent. Crude BSA sample could be purified on the IMAC column.     

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     

Synergistic Properties of Arabinogalactan (AG) and Hyaluronic Acid (HA) Sodium Salt Mixtures

The properties of mixtures of two polysaccharides, arabinogalactan (AG) and hyaluronic acid (HA), were investigated in solution by the measurement of diffusion coefficients D of water protons by DOSY (Diffusion Ordered SpectroscopY), by the determination of viscosity and by the investigation of the affinity of a small molecule molecular probe versus AG/HA mixtures in the presence of bovine submaxillary mucin (BSM) by ¹HNMR spectroscopy. Enhanced mucoadhesive properties, decreased mobility of water and decreased viscosity were observed at the increase of AG/HA ratio and of total concentration of AG. This unusual combination of properties can lead to more effective and long-lasting hydration of certain tissues (inflamed skin, dry eye corneal surface, etc.) and can be useful in the preparation of new formulations of cosmetics and of drug release systems, with the advantage of reducing the viscosity of the solutions.